Error of % + digits?

[Commander Kinsey]

I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?

[Commander Kinsey]

On Thu, 18 Jun 2020 14:03:42 +0100, Commander Kinsey <CFKi...@military.org.jp> wrote:

> I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?

Answering my own question, I found this page, it means aswell as the percentage error, the last digit (eg the 2 in 147.2V) can vary by 3.:

https://www.baylor.edu/content/services/document.php/49697.pdf

[Pimpom]

On 6/18/2020 6:33 PM, Commander Kinsey wrote:
> I just bought an amp clamp meter, and it states the error is "+/- 1.9% + 3 digits". What does the "3 digits" part mean?
>

If your meter should read, say 1.875 A, the correct reading could
be anywhere from 1.872 to 1.878. This is a possible error in the
display presented to you in the analog-digital display conversion
process. The +/-1.9% possible error is about the measurement
taken including - but not only - any error made by the sensor.

To put it another way: If the actual current is 1.875 A,
inaccuracies in the sensor and associated circuits may process it
as somewhere between 1.875 A +/-1.9%. The analog-digital process
may introduce a further error of +/- 3 counts in the least
significant display digit. Therefore a current of 1.875 A may be
displayed as anywhere from 1.836 to 1.913 A.

[Commander Kinsey]

Thanks, I wonder why all my other meters only list a % error. Is it included within it somehow, or are they just lying, or do some meters not have this error?

[Ralph Mowery]

In article <op.0meweog5wdg98l@glass>, CFKi...@military.org.jp says...

>
> > If your meter should read, say 1.875 A, the correct reading could
> > be anywhere from 1.872 to 1.878. This is a possible error in the
> > display presented to you in the analog-digital display conversion
> > process. The +/-1.9% possible error is about the measurement
> > taken including - but not only - any error made by the sensor.
> >
> > To put it another way: If the actual current is 1.875 A,
> > inaccuracies in the sensor and associated circuits may process it
> > as somewhere between 1.875 A +/-1.9%. The analog-digital process
> > may introduce a further error of +/- 3 counts in the least
> > significant display digit. Therefore a current of 1.875 A may be
> > displayed as anywhere from 1.836 to 1.913 A.
>
> Thanks, I wonder why all my other meters only list a % error. Is it included within it somehow, or are they just lying, or do some meters not have this error?
>
>

Most that use a digital meter should know the last digit is not accurate
because of a rounding error. Say it shows 1.5 volts. It could be 1.45
to 1.55 or so and still show 1.5. Some meters such as the one under
discussion is less accurate and can be 3 numbers high or low on the last
digit. That is why on digital meters you should try to use a range that
shows as many digits as you can.

-My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1
digit.

[Commander Kinsey]

Yes, but I was surprised to see up to 7 digits out on this one, depending on the range. I think DC amps is 3 or 5 dependant on range, and AC amps is 5 or 7.

> -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1
> digit.

The meters I have are not several hundred dollars, so are you saying they're only +/- 1 digit? Is the error much higher on the one under discussion because it's a clamp meter?

[Ralph Mowery]

In article <op.0mfizcwhwdg98l@glass>, CFKi...@military.org.jp says...

> > -My several hundred dollar Fluke meter shows DC volts to be .05 % +- 1
> > digit.
>
> The meters I have are not several hundred dollars, so are you saying they're only +/- 1 digit? Is the error much higher on the one under discussion because it's a clamp meter?
>
>

The larger error is because of the price difference. It costs more to
make a part that is .01 % than it does to make one that is 2 %. The
.01% parts may just be the 2 % ones that are hand sorted to .01%.

I am sure that the clamp part does play some part in how accurate the
meter is.

[Commander Kinsey]

But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays?

[Ralph Mowery]

In article <op.0mg7zmz6wdg98l@glass>, CFKi...@military.org.jp says...

>
> But what I'm surprised at is a £5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays?
>
>

You have to be careful how you throw precision and accurecy around.

A meter that shows 4 digits is more precice than one that shows only 3
digits, however the 4 digit one may only be 1% accurate and the 3 digit
one may be .5% accurate.

It is easy to get precision, but difficule to be accurate. Think of it
as shooting a gun. Precision may be how close the bullets land to each
other where ever they land on the target, but to be accurate the bullets
have to land on the center of the target. Such as all the bullets could
land very close to each other, but not even hit the target.

As I mentioned, a good meter will not have a digits error outside the +-
one digit due to rounding.

[Commander Kinsey]

That didn't help. I interchange the two. I just want to know how close to the correct reading the readout is. Adding another digit doesn't improve anything if it's incorrect. And shooting all the bullets in one place doesn't help if they all miss.

[Pimpom]

Take pi as an example. It can be said that 3.14 is accurate as a
three-digit value, but 3.1416 is more precise because it has a
higher resolution.

OTOH, deriving it from 22/7 or 3.1429 has the same 5-digit
resolution and is just as precise as far as the number it
represents is concerned but is less accurate.

In this particular case, 3.1416 is both more precise and more
accurate than 3.14 but that's not always the case with measurements.

My mechanical slide caliper has a resolution of 0.001 inch. This
means that it can display measurements with a precision of 1 mil,
but that doesn't guarantee that a measurement taken with it will
be accurate to 1 mil. I may not always press the jaws snugly
enough and the scale may not be perfectly accurate.

[Commander Kinsey]

I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage.

[Ralph Mowery]

In article <op.0miefkhkwdg98l@glass>, CFKi...@military.org.jp says...

>
> I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage.
>
>

Try this.

A doctor does a very complicated operation on your left arm like a joint
replacement. It all goes very well. Very precise.

However he should have done the operation on the right arm that was
causing trouble. Not accurate.


That is why a voltmeter can show 3 digits and be accurate to only the
last digit being in question by one number either way, but a 5 digit
volt meter can show many numbers, but if it is not calibrated corrctly
the 2nd digit to the 5 th digit could be way off and the meter not
accurate at all.

[Commander Kinsey]

On Sat, 20 Jun 2020 16:24:41 +0100, Ralph Mowery <rmower...@earthlink.net> wrote:

> In article <op.0miefkhkwdg98l@glass>, CFKi...@military.org.jp says...
>>
>> I'd need to contract OCD to understand that. There's only one thing in question here, how close is the reading to the correct value. You can't split that into two. 3.1416 is better than 3.14, and that's it. All you can state with a reading is it's correct to within a certain percentage.
>
> Try this.
>
> A doctor does a very complicated operation on your left arm like a joint
> replacement. It all goes very well. Very precise.
>
> However he should have done the operation on the right arm that was
> causing trouble. Not accurate.

Nope, because the first one is 100% useless. I wouldn't call that precise at all, as he was out by half a metre.

> That is why a voltmeter can show 3 digits and be accurate to only the
> last digit being in question by one number either way, but a 5 digit
> volt meter can show many numbers, but if it is not calibrated corrctly
> the 2nd digit to the 5 th digit could be way off and the meter not
> accurate at all.

Showing those extra two numbers is pointless if they're wrong. All that matters is how many volts difference between the actual voltage and what is shown.

[Pimpom]

You keep saying that it's only the accuracy that matters. That's
true to some - and only some - extent.

Now let's compare two different hypothetical meters, both 100%
accurate. Let's say that meter A has 3.5 digits (max count 1999)
and meter B is 4.5 digits (19999). Use them to measure a battery
cell of exactly 1.612345V.

Meter A will display 1.612V whereas meter B will show 1.6123V.
Meter B allows you to evaluate the result to a higher degree of
precision.

Further suppose that both meters are not perfectly accurate and
read 1% low. A will show 1.596V while B will read 1.5962V. B is
still more precise in showing you what it thinks the voltage is.
An order of magnitude more precise, in fact, even though both
meters are off by -1%.

That's how the term 'precision' is used in engineering. Perhaps
what's confusing you is the fact that the term is more loosely
applied in everyday language.

As to the +/- 3 count (or 1 or whatever) possible error, it's an
*uncertainty*, not a fixed inaccuracy, in digitizing an analog
quantity. It will take too long to explain in detail here. Let me
put it this way: If you measure the example voltage above
multiple times with a meter with +/-3 count uncertainty, you may
get a reading that varies from measurement to measurement by up
to 6 points in the last digit. That's not a percentage inaccuracy.

[Ralph Mowery]

In article <U6sHG.61028$Nj4....@fx24.ams1>, nob...@nowhere.com says...

>
> You keep saying that it's only the accuracy that matters. That's
> true to some - and only some - extent.
>
>
>

Sometimes it is precision.

I worked at a company making polyester from raw materials. In a room
was a panel with about 10 temperature gauges. At a certain time all
gauges were marked and a sample of the material was sent to the lab. If
it came back good, then the object was to keep all the gauges on the
mark. It did not matter how far off the gauges were from the actual
temperature. No mater how well we calibrated the guages there were
several other factors that we had no control over. Such as the
thermocouples they were connected to. The specifications were +- 3 deg
C. on the thermocouples from the factory. If the temperature varied
more than 1 deg C at 300 deg C it could mess up the material.

So the object was precision and not accuracy.

[Jeroen Belleman]

On 2020-06-20 17:58, Commander Kinsey wrote:
[...]

>
> Showing those extra two numbers is pointless if they're wrong. All
> that matters is how many volts difference between the actual voltage
> and what is shown.

Engineers distinguish between accuracy, a measure of how close
a observed value is to the true value, and resolution, which
is a measure of the device's ability to resolve small changes.
Either specification is useful in its own right, and professional
instrumentation will always have both specs. So even if the
last digit or two of a measuring device are not accurate, they
may still be useful.

You may want to check audio ADCs and DACs for example, which
have atrocious accuracy, but excellent resolution. An example
of the opposite might be a voltage reference, which has excellent
accuracy, but no resolution at all.

Of course in general, there is a tendency of accurate instruments
to have a better resolution too.

Jeroen Belleman

[Tom Gardner]

I once worked for a company that made an instrument that
measured cable attenuation to 0.001dB +- 0.1dB. The customers
didn't care about the 0.1dB, since all they were interested
in was the /stability/ of the 0.001dB and the ability to
measure small changes.

Why? Because the instrument measured the attenuation change
as a function of temperature, and each temperature cycle
test took 7 days. Yes, it was a /large/ drum of undersea cable.

[Dieter Michel]

Hi,

> I just bought an amp clamp meter, and it states the error is "+/- 1.9% +
> 3 digits".  What does the "3 digits" part mean?

I'll try to explain that with a simplified model of
a digital meter (please everybody correct me if it's
oversimplified and wrong):

The typical digital meter consist of some kind of
processing of the signal to be measured and an
A/D-converter that converts it's analog input
signal to a number that is displayed.

The input processing serves to transform the quantity
to be measured into an analog signal that is properly
adapted to cover the range of possible input signals
of the A/D-converter.

Let's say we want to measure an AC current of 10A with
a clamp meter like yours. Let the display of the meter
have 3 1/3 digits, so the range of displayable numbers
goes from 0000 to 1999 with an additional decimal point
somewhere.

The A/D-converter will not be able to directly convert
a 10A current, so we pickup the current to be measured
with a transformer, the wire carrying your 10A current
being the primary and a coil internal to the clamp
assembly being the secondary winding.

An AC current flow through the wire will induce an AC voltage
in the secondary winding. Since the A/D-converter may not
directly accept AC voltages, further processing may be
required, such as amplification or voltage division and
e.g. True-RMS detection of the AC voltage. All this
processing will end up in a voltage that is suitable for
the A/D-converter - say, 1V DC for 10A of AC current.

All the (analog) signal processing described here will
not be free of unwanted influences and processing errors.
The transformer at the input could e.g. pick up unwanted
magnetic fields, the amplifier could exhibit noise and
nonlinearities, the TRMS detection could exhibit some errors.

All these error sources or influences may be described in
the meter's specification as a percentage - e.g. the +/- 1.9%
you mentioned.

Now, the A/D converter converts the analog input voltage
into a number. One method to do this, when speed is not
a critical factor, is (dual) slope integration.

Let's assume for a moment that the input voltage is static,
i.e. the 1V DC mentioned before.

Basically, the conversion works by comparing the input
voltage (to be measured) to a linearly rising voltage
(ramp). Similar to a stopwatch, a counter starts when
the reference voltage begins to rise and a comparator
stops it when the ramp voltage is equal to the input voltage.

In our example with 1V input, the counter may stop at a
count of 1000. With the knowledge that, by means of the
input processing and the calibration of the meter, this
corresponds to 10A AC current. The meter would probably
display 10.00 (A).

But: At some time in the process, the counter will switch
from 999 to 1000 in a very short (almost zero) time.
That means, that the input voltage may just be a tiny little bit
less and the counter is stopped at 999, not at 1000.

That means, that for any input signal, you always have +/-1 digit
display uncertainty because you cannot know whether the
counter maybe was just before switching to the next count.

With a specification of +/-3 digits, the A/D converter has
a greater uncertainty when counting. For example, even at
a constant input of 1V, the internal counter may be less
precise and stop at 997, 998, 999, 1000, 1001, 1002 or 1003,
even if the input signal doesn't change. You can think of
this as a stopwatch that may be off some counts each time
you make a measurement.

This type of error is not related to the input signal
processing, so it is not very meaningful to express the
error as a percentage of the measured value. It is usually
expressed as a number of digits, because the error is mainly
caused by the process of converting input signals to numbers.

Of course, I know that this very simple single slope integration
is not used in meters, dual slope is the least you can do.
Also, the A/D conversion may contribute to the percentage error spec.
The (over)simplification is just a means to explain why there
are two numbers in the specification.

Just my two cents,

Dieter

[Commander Kinsey]

On Sat, 20 Jun 2020 19:18:24 +0100, Jeroen Belleman <jer...@nospam.please> wrote:

> On 2020-06-20 17:58, Commander Kinsey wrote:
> [...]
>>
>> Showing those extra two numbers is pointless if they're wrong. All
>> that matters is how many volts difference between the actual voltage
>> and what is shown.
>
> Engineers distinguish between accuracy, a measure of how close
> a observed value is to the true value, and resolution, which
> is a measure of the device's ability to resolve small changes.
> Either specification is useful in its own right, and professional
> instrumentation will always have both specs. So even if the
> last digit or two of a measuring device are not accurate, they
> may still be useful.

I can see that, although when I've had an instrument with more digits than its accuracy, it usually has a fluctuation of its own (perhaps through interference from inadequate shielding), so I can't actually tell if the real value has changed.

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
> I just bought an amp clamp meter, and it states the error is "+/-
> 1.9% + 3 digits". What does the "3 digits" part mean?

The "3 digits" part is a measure of absolute error (i.e., the amount of
error that does not depend upon the magnitude of the value being
measured). The percentage part is a measure of relative error (i.e.,
the amount of error that does depend upon the magnitude of the value
being measured).

So if you clamp around a wire and get a reading of 1.234A on the
display, then the actual current in the wire could be anywhere within
this range:

1.234 +/- (1.234 * 0.019) +/- 0.003

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:

> On Thu, 18 Jun 2020 15:38:46 +0100, Pimpom <nob...@nowhere.com> wrote:
>
>> On 6/18/2020 6:33 PM, Commander Kinsey wrote:
>>> I just bought an amp clamp meter, and it states the error is "+/-
>>> 1.9% + 3 digits". What does the "3 digits" part mean?
>>>
>>
>> If your meter should read, say 1.875 A, the correct reading could
>> be anywhere from 1.872 to 1.878. This is a possible error in the
>> display presented to you in the analog-digital display conversion
>> process. The +/-1.9% possible error is about the measurement
>> taken including - but not only - any error made by the sensor.
>

> Thanks, I wonder why all my other meters only list a % error. Is it
> included within it somehow, or are they just lying, or do some meters
> not have this error?

One generally finds the percentage plus digits error measures on more
expensive equipment. Less expensive equipment more often than not only
lists a percentage and nothing more.

[Cydrome Leader]

In sci.electronics.equipment Pimpom <nob...@nowhere.com> wrote:
> On 6/20/2020 4:29 AM, Commander Kinsey wrote:
>> On Fri, 19 Jun 2020 23:55:42 +0100, Ralph Mowery <rmower...@earthlink.net> wrote:
>>
>>> In article <op.0mg7zmz6wdg98l@glass>, CFKi...@military.org.jp says...
>>>>

>>>> But what I'm surprised at is a ?5 multimeter (not clamp) not giving a digits error. Maybe precision on a simple voltmeter is cheap as chips nowadays?

>>>>
>>>>
>>>
>>> You have to be careful how you throw precision and accurecy around.
>>>
>>> A meter that shows 4 digits is more precice than one that shows only 3
>>> digits, however the 4 digit one may only be 1% accurate and the 3 digit
>>> one may be .5% accurate.
>>>
>>> It is easy to get precision, but difficule to be accurate. Think of it
>>> as shooting a gun. Precision may be how close the bullets land to each
>>> other where ever they land on the target, but to be accurate the bullets
>>> have to land on the center of the target. Such as all the bullets could
>>> land very close to each other, but not even hit the target.
>>>
>>> As I mentioned, a good meter will not have a digits error outside the +-
>>> one digit due to rounding.
>>
>> That didn't help. I interchange the two. I just want to know how close to the correct reading the readout is. Adding another digit doesn't improve anything if it's incorrect. And shooting all the bullets in one place doesn't help if they all miss.
>>
>
> Take pi as an example. It can be said that 3.14 is accurate as a
> three-digit value, but 3.1416 is more precise because it has a
> higher resolution.
>
> OTOH, deriving it from 22/7 or 3.1429 has the same 5-digit
> resolution and is just as precise as far as the number it
> represents is concerned but is less accurate.
>
> In this particular case, 3.1416 is both more precise and more
> accurate than 3.14 but that's not always the case with measurements.
>
> My mechanical slide caliper has a resolution of 0.001 inch. This
> means that it can display measurements with a precision of 1 mil,

What if your caliper had a resolution of 1 mil +/- 3 counts on the last
digit? That's the issue with multimeters that have completely bogus digits
at the end. Those number are just noise and serve no purpose at all. They
don't even compare to all bullets missing the target but landing in the
same wrong spot.

[Cydrome Leader]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:

agreed. The problem with the bullets and the target story is that when
explained, we somehow perfectly know where the bullets are- be in on
target or a small grouping somewhere else. Cheapo meters won't give
CONSISTENT or REPEATABLE results, not matter how "precise" they pretended
to be, or how accurate the spec sheet claims, especially considering the
last digit(s) may be totaly wrong, and random. It's like having crappy or
dirty test leads or a component. You'll get all the digits in the world,
but they keep changing. You won't even be able to pick a reading.

Keep in mind that "calibrated" equipment doesn't even have to be precise
or accurate. An example would be an adjustable power supply with digital
readout. Say it's always reads high by 0.7 volts. It's not precise or
accurate, but by knowing the offset it can used with success and may even
have great regulation.

On the other hand say you have an alibaba special power supply that's
"accurate" to +/- 0.35 volts, with terrible regulation that oscillates.

What power supply is better?

So the point is cheapo equipment can have lots of bogus digits and
readings that flop up and down, while better equipment can be more
consistently wrong, which can be compensated for. Precision and accuracy
mean little by themselves if you need multiple readings.

[Cydrome Leader]

If the goal was keep the needle on their marks it does't have to mean
anything was precise. Maybe your guages had no faces, or read mA instead
of degrees, and bent needles. As long as your +/- 3 degree thermocouples
and controllers did not jump up and down + and then -3 degrees all the
time, you were good.

It's like the zener diode or voltage standard that came up in this thread.
Those have no precision. They may not even be accurate. They might be
consistent though. Accuracy and precision by themselves can be useless
where time or multiple readings are needed.

[Pimpom]

You seem intent on picking an argument by inserting a statement
that agrees with the following sentences. BTW, my caliper is not
digital, so the matter of +/- count is irrelevant.

[Ralph Mowery]

In article <rd400g$egj$2...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> > So the object was precision and not accuracy.
>
> If the goal was keep the needle on their marks it does't have to mean
> anything was precise. Maybe your guages had no faces, or read mA instead
> of degrees, and bent needles. As long as your +/- 3 degree thermocouples
> and controllers did not jump up and down + and then -3 degrees all the
> time, you were good.
>
>

One good example of what we had is this.

In a vat of material is a test hole. In that hole is a rod about 3/8
inch in diameter and a foot long. At the end there are two
thermocouples and two RTDs. The thermocouples wires go about 100 feet
to a PLC (similar to a computer) card that converts the milivolts to
digital that is then displayed on a compute screen. The RTDs go about
10 feet to a converter that converts the change in resistance to a 4 to
20 miliamp signal. That goes to a card on the PLC and then to the
computer display.

While the computer will display to 3 decimal places at 300 deg C from
the lowest to the highest temperature shown on the display can be around
3 deg differnet and all 3 be within the limits of the equipmnet.

At a certain time a sample is sent to the lab and one of the computer
displays is set as a standard and the object of the PLC is to keep the
actual temperature , whatever it actually is, to that 'standard'. Not
too accurate as to temperature, but very precice. The operators only
needed to keep that one computer display as close to that 'mark' as they
can if for some reason the PLC messes up and they have to adjust the
control manual.

[Cydrome Leader]

What's the control loop if the PLC dies? How do people control temperatures
manually? Is there a foot pedal to stomp on to switch the heaters on and
off?


There's a couple machines I fuss with that use platinum junction RTDs and
we have alarm limits set. If the machine drifts into an alarm state,
outside of a warmup period that's pretty much the end of the day and
everything stops until it can be fixed. The loops on these machines are
tuned to maintain and hold a set point of less than 1 degree F. The
displays are all wrong, show fake levels of precision, and read in C, but
are wrong by several degrees, even if you do the math. We gave up trying to
calibrate the displays against what the real temperature with the offset
features when the probes were last changed. It just isn't worth the time.
Those machines are not accurate, they're not precise (as measured with
their own instrumentation), but they will absolutely hold a stable
temperature if you can determine the set points yourself.

[Cydrome Leader]

In sci.electronics.basics Pimpom <nob...@nowhere.com> wrote:
> On 6/26/2020 9:53 AM, Cydrome Leader wrote:
>> In sci.electronics.equipment Pimpom <nob...@nowhere.com> wrote:
>>>
>>> My mechanical slide caliper has a resolution of 0.001 inch. This
>>> means that it can display measurements with a precision of 1 mil,
>>
>> What if your caliper had a resolution of 1 mil +/- 3 counts on the last
>> digit? That's the issue with multimeters that have completely bogus digits
>> at the end. Those number are just noise and serve no purpose at all. They
>> don't even compare to all bullets missing the target but landing in the
>> same wrong spot.
>>
> You seem intent on picking an argument by inserting a statement
> that agrees with the following sentences. BTW, my caliper is not
> digital, so the matter of +/- count is irrelevant.

electronic test equipment is digital these days, so my question is very
valid.

How would you feel if your vernier or thimble readouts on your hand tools
had number that randomly moved around? That's the goofiness of how these
digital integrating meters work. It makes very little sense when directly
translated into the physical word.

Take a 100 foot surveyor's tape measure. Those are simple to read. You have
feet and inches, and they're all in order. Let's our 100 foot tape is
accurate to 3inches over that 100 feet. Not great, but fine for us.

Now go digital, with the analog feel. Say the tape is now a long e-ink
display and has no factory printed numers on it like a conventional tape.
Every time you pull the tape out it redisplays tape measure printing and
you get stuff like this:

... 12ft 1in 2in 4in 5in 3in 6in 7in 8in 9in 11in 10in 13ft ...

How would that feel?

It makes absolutely no sense unless you understand the silly types of
errors that are display on devices where we expect direct read out of
numbers.

>>> but that doesn't guarantee that a measurement taken with it will
>>> be accurate to 1 mil. I may not always press the jaws snugly
>>> enough and the scale may not be perfectly accurate.

crappy meters can lack "snug" readings.

[Ralph Mowery]

In article <rd6pl5$42t$1...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> What's the control loop if the PLC dies? How do people control temperatures
> manually? Is there a foot pedal to stomp on to switch the heaters on and
> off?
>
>
>

The process has two PLCs running all the time. There are two or more
computers hooked to the data stream for the PLCs One PLC is the so
called hot backup. It is not controlling, but if the primary one quits,
the secondary one will either switch over automatically or it can be
manually switched.

One thermocouple is connected to the control loop. If that TC goes bad,
there are other TCs that give the temperature readout and the operators
switch the control screen for that temperature to manual and they have
to keep an eye on it and manually enter on the computer keyboard what
percentage of valve opening is needed to mantain the correct
temperature.

[Cydrome Leader]

In sci.electronics.basics Ralph Mowery <rmower...@earthlink.net> wrote:

OK, so if a PLC croaks, the operators can switch to the redundant one. If a
probe of whatever you have between it and the current loop or whatever it
was fails, it's 100% manual control? How do you share the reading from one
problem? Not trying to pole holes in theory here, just actually curious.

One thing annoying about the probes I deal with is it seems no two are
alike. Never been able to swap one for another, even with short leads, even
with three lead compensation and get the same behavior on the same
controller.

[Ralph Mowery]

In article <rdblel$f8m$5...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> OK, so if a PLC croaks, the operators can switch to the redundant one. If a
> probe of whatever you have between it and the current loop or whatever it
> was fails, it's 100% manual control? How do you share the reading from one
> problem? Not trying to pole holes in theory here, just actually curious.
>
> One thing annoying about the probes I deal with is it seems no two are
> alike. Never been able to swap one for another, even with short leads, even
> with three lead compensation and get the same behavior on the same
> controller.
>
>

Here is sort of how it works. One PLC quits. The second PLC takes over
automatically or can be switched manually at any time.


A TC feeding the PLCs fails. An alarm is sounded as the PLC thinks the
process has gone out of limits. The operator is at a computer (was
running a graphics program on Win XP when I left) , He calls up the
control screen and puts the control in manual and sets the signal to the
valve to where it was before the device fails. There is a secondary
temperature TC. The operator looks back in the history of the read outs
and sees that the primary control TC was showing 300.2 deg C when the
lab said the process was on target. At the same time the secondary TC
was showing 301.6 deg C. So the operator now has the control in manual
and adjusts the output of the contoler to try and keep the process at
301.6 deg C showing on the readiout now.

When the bad TC is replaced and the process is checked out by the lab,
The new setting may come back as 301.1 deg C. So that will be the new
target.

The vessels are large enough , around 10 feet tall and 5 feet in
diameter so the temperature change takes a long time.

The process is making polyester material. We put in a powder that looks
like flour and a liquid Glycol. It is heated to about 300 deg C. There
are 5 vessels in the process and it is continious. The powder and
liquid are put in the first vessel and at the bottom is a pipe that
conveys it to the next one. The process is repeated and small ammouts
of other chemicals are added at each stage. It is extruded after the
last vessel to what looks like string.
It takes about 15 hours for the material to make it from start to
finish. We make about 3000 pounds to 10,000 pounds of material each
hour depending on the size of the process line.

About 2 years ago the plant that had around 3000 people 20 years ago
went out of business. Mostly because of other countries makeing the
material much cheaper.

[Commander Kinsey]

So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?

[Cydrome Leader]

In sci.electronics.equipment Ralph Mowery <rmower...@earthlink.net> wrote:

Interesting.

I met an engineer who worked at Eastman decades ago. He had good stories
about the complexity of starting a new production line of chemicals or
plastics whatever they were making at the time. The amusing part was none
of the people that designed the new systems could never get the first
batches to work at full scale. They'd have an old timer operator figure it
out for them after they all gave up. This process could take days.

The final "say" on the machines I deal with are the colors of test strips
that run through the entire process.

[Cydrome Leader]

might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
have been from a raffle or something like that.

The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
AC ranges which are "1.2% RDG +10 Digits". If I had new leads, I'd trust it
with outlet voltage, but would stay away from 208volts. The meter has 3.5
digits or max display of 1999. I'm figuring a real 100volt AC reading could
be 99 to 101 plus another error of +/- 1 volt for the 10 digits tolerance
on the display or count. so 100volts from your Japanese outlet reference
might read 98 to 102 volts. So while in the ballpark, it's better than you
can read off a Simpson 260 meter in the AC voltage range. I could be wrong
on this too.

It's a pretty decent meter for poking at DC circuits for the tens of
dollars is must have cost when new.

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
> On Wed, 24 Jun 2020 21:06:04 +0100, Rich <ri...@example.invalid> wrote:
>
>> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>>> On Thu, 18 Jun 2020 15:38:46 +0100, Pimpom <nob...@nowhere.com> wrote:
>>>
>>>> On 6/18/2020 6:33 PM, Commander Kinsey wrote:
>>>>> I just bought an amp clamp meter, and it states the error is "+/-
>>>>> 1.9% + 3 digits". What does the "3 digits" part mean?
>>>>>
>>>>
>>>> If your meter should read, say 1.875 A, the correct reading could
>>>> be anywhere from 1.872 to 1.878. This is a possible error in the
>>>> display presented to you in the analog-digital display conversion
>>>> process. The +/-1.9% possible error is about the measurement
>>>> taken including - but not only - any error made by the sensor.
>>>
>>> Thanks, I wonder why all my other meters only list a % error. Is
>>> it included within it somehow, or are they just lying, or do some
>>> meters not have this error?
>>
>> One generally finds the percentage plus digits error measures on
>> more expensive equipment. Less expensive equipment more often than
>> not only lists a percentage and nothing more.
>
> So should I assume the cheaper ones are lying?

More likely they simply invested less effort in measuring their
respective meters accuracy. And a generally safe assumption is that
lower cost often equates to less accurate.

> Or have they just made a rough estimate adding the two errors?

This is likely, but without being able to ask the maker, anything we
surmise here is just a guess anyway.

[Ralph Mowery]

In article <rdecuc$m73$1...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> > So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?
>
> might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
> have been from a raffle or something like that.
>
> The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
> AC ranges which are "1.2% RDG +10 Digits". If I had new leads, I'd trust it
> with outlet voltage, but would stay away from 208volts. The meter has 3.5
> digits or max display of 1999. I'm figuring a real 100volt AC reading could
> be 99 to 101 plus another error of +/- 1 volt for the 10 digits tolerance
> on the display or count. so 100volts from your Japanese outlet reference
> might read 98 to 102 volts. So while in the ballpark, it's better than you
> can read off a Simpson 260 meter in the AC voltage range. I could be wrong
> on this too.
>
> It's a pretty decent meter for poking at DC circuits for the tens of
> dollars is must have cost when new.
>
>

It seems that maybe due to modern manufactoring the meters are more
accurate than they were 20 years ago. I bought some DC voltmeters from
China. They display 3 digits. They read from 0 to 99.9 volts. I coulg
get 4 of them for less than $ 15 including the shipping. I hooked all 4
of them in parallel with a Fluke 87 . Three of them tracked right along
with the Fluke with the last digit sometimes being one high or low from
0 to 24 volts. The fourth one was off by an average of 2 on the last
digit. I found an adjustment screw on the back of the meter and tweaked
it and re ran the test. It then fell in line with the other meters.

I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
usually sell for around $ 5. They seem to be reasonable accurate for
the money. Plenty accurate for the home user to test things around the
house. I do admit that the safety issue of putting them across the 120
or 240 volt power wires is somewhat doubtful. I sure would not use one
where I worked to put across the 480 volt 3 phase system that is fused
with 200 amps.

[Cydrome Leader]

In sci.electronics.equipment Ralph Mowery <rmower...@earthlink.net> wrote:

Have you run this test with AC? That seems to be where the wheels come
off. I brought up this thread to a friend and he mentioned his quest to
repair some sort of HP true RMS meter that uses a thermocouple and heater
to properly measure complex waveforms. I can't even guess how slow such a
meter might be.

> I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
> usually sell for around $ 5. They seem to be reasonable accurate for
> the money. Plenty accurate for the home user to test things around the
> house. I do admit that the safety issue of putting them across the 120
> or 240 volt power wires is somewhat doubtful. I sure would not use one
> where I worked to put across the 480 volt 3 phase system that is fused
> with 200 amps.

I'm pretty timid with anything upstream from a plain outlet. I had an
edison base fuse burst in my hand once. Never seen one come apart before.
It was just a 120v lighting circuit, but right off the service panel.
There's way more excitement near those things.

[Jasen Betts]

The heaters used in thermal printers manage a speed better than 10mS
stuff done in a microchip (like LT1088) could be even faster.

--
Jasen.

[Ralph Mowery]

In article <rdjsa6$28b$1...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> Have you run this test with AC? That seems to be where the wheels come
> off. I brought up this thread to a friend and he mentioned his quest to
> repair some sort of HP true RMS meter that uses a thermocouple and heater
> to properly measure complex waveforms. I can't even guess how slow such a
> meter might be.
>
> > I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
> > usually sell for around $ 5. They seem to be reasonable accurate for
> > the money. Plenty accurate for the home user to test things around the
> > house. I do admit that the safety issue of putting them across the 120
> > or 240 volt power wires is somewhat doubtful. I sure would not use one
> > where I worked to put across the 480 volt 3 phase system that is fused
> > with 200 amps.
>
> I'm pretty timid with anything upstream from a plain outlet. I had an
> edison base fuse burst in my hand once. Never seen one come apart before.
> It was just a 120v lighting circuit, but right off the service panel.
> There's way more excitement near those things.
>
>

I have not ran any tests for AC . The things I work with don't care
about very much about being accurate to more than around 5 %. Usually
it is more of do I have a voltage/current or not.

When I work on most anything other than low voltage (below 100 volts) I
ues either my Simpson 260 analog meter or a Fluke meter that is rated
for cat 3 and 4. If you have not heard of the Cat numbers, they are for
devices used in different power circuits. I don't know the numbers off
hand, but it goes something like this, Cat 1 is for low voltage items,
Cat 2 for things like stoves and refrigerators, Cat 3 for homw
wiring,and Cat 4 for the very high power circuits like I often worked on
like the 480 volt AC and 300 amps.

For a real scare you should see some of the safety movies that Fluke put
out. They show under test conditions what can hapen to inexpensive
meters and their meters under different conditions like having the
meter set for amps and putting across a 480 volt circuit that has plenty
of amps .

[RheillyPhoull]

Ahh the old "Leaving it on amps" trick. How many of us can say they
never did it ?

[Jasen Betts]

or even just this document.

https://content.fluke.com/promotions/promo-dmm/0518-dmm-campaign/dmm/fluke_dmm-chfr/files/safetyguidelines.pdf

--
Jasen.

[Ralph Mowery]

In article <rdnant$2sm$3...@gonzo.revmaps.no-ip.org>, ja...@xnet.co.nz
says...

>
> > I have not ran any tests for AC . The things I work with don't care
> > about very much about being accurate to more than around 5 %. Usually
> > it is more of do I have a voltage/current or not.
> >
>
>

Just for the fun of it, I did test the 3 'free' Harbor Freight meters on
AC and DC yeaterday. From 0 to 25 VDC the HF meters were within about
.5 % of the Fluke meter. On AC up to 130 VAC they were around 3 %. One
was always low and the other 2 were always high.

So they are accurate for most anything around the house for most people.

[Commander Kinsey]

I've got thermostats like that, I've calibrated them to 0.1C. Trouble is, they have remote sensors which work perfectly, but if the actual unit gets very warm (as in direct sunlight), the reading goes up by as much as 2C. Nevermind, they happen to be in my conservatory (the main source of heat in the summer), along with the air conditioner, so on a hot day they switch it on slightly too soon, then correct themselves when the AC cools them off.

[Commander Kinsey]

In America, what is a "mill"? In the UK, it used to mean a thousandth of an inch, but people use it to mean a millimetre nowadays.

[Pimpom]

On 7/12/2020 11:15 PM, Commander Kinsey wrote:
> On Fri, 26 Jun 2020 05:23:31 +0100, Cydrome Leader <pres...@mungepanix.com> wrote:
>
>> In sci.electronics.equipment Pimpom <nob...@nowhere.com> wrote:

>>> My mechanical slide caliper has a resolution of 0.001 inch. This
>>> means that it can display measurements with a precision of 1 mil,
>>
>> What if your caliper had a resolution of 1 mil +/- 3 counts on the last
>> digit?

.....<snip>........

>
> In America, what is a "mill"? In the UK, it used to mean a thousandth of an inch, but people use it to mean a millimetre nowadays.
>

It's not a mill. It's mil - single l. It means, and has always
meant, a thousandth of an inch. It's not an Americanism.

[Tom Gardner]

In the UK "mill" means millilitre.

If you want to refer to fractions of an inch, then
it is /always/ "thou", i.e. thousandths of an inch.

In the UK "mil/mill" /never/ means 0.001".

[Cydrome Leader]

Is it the controller that's off by 2C when it warms up?

[Pimpom]

My bad. This is the first time I heard that the mil is not used
as the unit for .001" in the UK. (I'm *not* an American).

[Commander Kinsey]

Yes. The controller is in the conservatory in direct sunlight. The sensor is on a long wire in a cooler room (the living room) which is what I want to control the temperature of. The controller's reading goes up by 2C if it gets really hot, but the AC blows across it, so it doesn't do it wrong for long.

[Commander Kinsey]

Yes it does. My neighbour's a tradesman (in Scotland) and says "mill/mil" (I don't know which as they sound the same in speech) as shorthand for millimetre. As in "that kitchen unit is 600 mill wide". Since we don't use inches for such things in the UK, there's no confusion.

[Commander Kinsey]

If you're not American why did you say "my bad"? Your bad what? Finish the sentence!

[Commander Kinsey]

I only expect such ambiguity from Australians. They say "6 Ks" to mean 6 km. I say the complete words. Kilometre, millimetre, millilitre, etc.

[Pimpom]

So now you're a grammar Nazi? This after I (and others) spent
considerable time and effort patiently explaining to you a
concept that many/most readers here probably already knew, and
would quickly grasp if they didn't. Sheesh!

And is there a law against non-Americans using an American
expression? FYI I'm none of these: American, British, Australian
or Canadian - or a citizen of any other country where English is
natively spoken.

[Jeroen Belleman]

On 2020-07-13 17:27, Pimpom wrote:
> On 7/13/2020 6:06 PM, Commander Kinsey wrote:

[...]

>> If you're not American why did you say "my bad"?  Your bad what?
>> Finish the sentence!
>>
> So now you're a grammar Nazi? This after I (and others) spent

> considerable time and effort[...]

Just drop it. There are better things to do than to argue
with a cantankerous teenager. If a conversation turns into
a source of irritation, the best way is to simply drop out.

Jeroen Belleman

[Tom Gardner]

Precisely.

That was my decision too. An easy decision given the moniker
"Commander Kinsey" is either someone that has too high a
regard for themselves, or is indicating that they intend to
troll.

[Cydrome Leader]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:

The context there is key too. While I'd not measure a countertop or
whatever in millimeters, it would make no sense that anything in a kitchen
would be measured thicknesses of paper.

We (in the US) use "guage" for wire and sheet metal. We also use "guage"
for measuring really thin stuff like plastic films. In the last case, it's
a completly different unit, but with proper context won't confuse anybody.

Question for the metric woodworkers. Does anybody cut a piece of wood to
317mm or 429mm or other off numbers when building a house or handing a
door or installing a countertop?

[Commander Kinsey]

Whyever not? Even the cheap ones usually state you can use them up to 1000 volts. I've used them on 240 and 415 just fine. I used one on 2000 volts once, and it just failed inside, not even smoke or noise.

[Commander Kinsey]

On Tue, 30 Jun 2020 04:52:44 +0100, Cydrome Leader <pres...@mungepanix.com> wrote:

> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>> On Wed, 24 Jun 2020 21:06:04 +0100, Rich <ri...@example.invalid> wrote:
>>
>>> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>>>> On Thu, 18 Jun 2020 15:38:46 +0100, Pimpom <nob...@nowhere.com> wrote:
>>>>
>>>>> On 6/18/2020 6:33 PM, Commander Kinsey wrote:
>>>>>> I just bought an amp clamp meter, and it states the error is "+/-
>>>>>> 1.9% + 3 digits". What does the "3 digits" part mean?
>>>>>>
>>>>>
>>>>> If your meter should read, say 1.875 A, the correct reading could
>>>>> be anywhere from 1.872 to 1.878. This is a possible error in the
>>>>> display presented to you in the analog-digital display conversion
>>>>> process. The +/-1.9% possible error is about the measurement
>>>>> taken including - but not only - any error made by the sensor.
>>>>
>>>> Thanks, I wonder why all my other meters only list a % error. Is it
>>>> included within it somehow, or are they just lying, or do some meters
>>>> not have this error?
>>>
>>> One generally finds the percentage plus digits error measures on more
>>> expensive equipment. Less expensive equipment more often than not only
>>> lists a percentage and nothing more.
>>
>> So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?
>
> might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
> have been from a raffle or something like that.
>
> The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
> AC ranges which are "1.2% RDG +10 Digits".

TEN!? Surely that's more than the number of digits it has? In which case it has no accuracy at all.

> If I had new leads, I'd trust it
> with outlet voltage, but would stay away from 208volts.

You oughta complain about that low voltage. Some equipment needs at least 220.

[Commander Kinsey]

How well do these things work measuring dodgy waves like from a cheap UPS or invertor?

>> I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
>> usually sell for around $ 5. They seem to be reasonable accurate for
>> the money. Plenty accurate for the home user to test things around the
>> house. I do admit that the safety issue of putting them across the 120
>> or 240 volt power wires is somewhat doubtful. I sure would not use one
>> where I worked to put across the 480 volt 3 phase system that is fused
>> with 200 amps.
>
> I'm pretty timid with anything upstream from a plain outlet.

I've replaced outlets (240V, not the namby pamby USA stuff) without turning off the power - other outlets on the same circuit were being used in the office and I saw no point in interrupting them.

Just keep your fingers off the metal things and don't short stuff together. Wear goggles and gloves if you want to be a girl about it.

> I had an
> edison base fuse burst in my hand once. Never seen one come apart before.
> It was just a 120v lighting circuit, but right off the service panel.
> There's way more excitement near those things.

Try shorting two phases together with 500A cables. That causes lots of smoke, a fire alarm, 3 fire engines, and a visit from the power company. Do not ever employ Irish electricians.

[Michael Terrell]

208 is a standard three phase voltage. It is three 120 volt lines phased 120 degrees apart.

[Commander Kinsey]

I find it crazy that you can select volts and have the wires in the amps holes. The switch should change the contacts. I've broken a meter doing that, just measuring the voltage on a car battery. £100 meter, but UNFUSED FFS! At least the mA range was fused, but they couldn't be bothered putting in a 20A fuse for the big range....

[Commander Kinsey]

Yes I've heard of them, they're a measurement scale for pansies.

> I don't know the numbers off
> hand, but it goes something like this, Cat 1 is for low voltage items,
> Cat 2 for things like stoves and refrigerators, Cat 3 for homw
> wiring,and Cat 4 for the very high power circuits like I often worked on
> like the 480 volt AC and 300 amps.
>
> For a real scare you should see some of the safety movies that Fluke put
> out. They show under test conditions what can hapen to inexpensive
> meters and their meters under different conditions like having the
> meter set for amps and putting across a 480 volt circuit that has plenty
> of amps .

Safety movies designed to sell Fluke meters, and you fell for them hook line and sinker.

[Ralph Mowery]

In article <op.0nuzmdi9wdg98l@glass>, CFKi...@military.org.jp says...

> I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
> > usually sell for around $ 5. They seem to be reasonable accurate for
> > the money. Plenty accurate for the home user to test things around the
> > house. I do admit that the safety issue of putting them across the 120
> > or 240 volt power wires is somewhat doubtful. I sure would not use one
> > where I worked to put across the 480 volt 3 phase system that is fused
> > with 200 amps.
>
> Whyever not? Even the cheap ones usually state you can use them up to 1000 volts. I've used them on 240 and 415 just fine. I used one on 2000 volts once, and it just failed inside, not even smoke or noise.
>
>

Because I have seen what damage can be done with those circuits.

I have also seen some safty films that the Fluke meter company put out.
Say you take your HF meter and by mistake have it on the ohms or amp
range. Normally an internal fuse would blow. However there is enough
power in the circuits to arc over the fuse, the meter leads instantly
almost explode or look like an arc welder. If you have one hand on each
lead it is possiable the insulation will melt off and maybe into your
hands. You could also become part of the circuit and fry.

Look here around the 6 minuit point.

https://www.youtube.com/watch?v=OEoazQ1zuUM

[Ralph Mowery]

In article <op.0nu3kdf9wdg98l@glass>, CFKi...@military.org.jp says...

>
> Safety movies designed to sell Fluke meters, and you fell for them hook line and sinker.
>
>

No, I have actually seen a few blowups and the results of some others.

Have you ever worked at a place that has lots of 480 volt 3 phase
equipment ? I did before retiring. One learns to respect what can
hapen.

[Michael Terrell]

He is just an arc flash away from making an ash of himself.

[Commander Kinsey]

On Thu, 16 Jul 2020 21:03:04 +0100, Ralph Mowery <rmower...@earthlink.net> wrote:

> In article <op.0nu3kdf9wdg98l@glass>, CFKi...@military.org.jp says...
>>
>> Safety movies designed to sell Fluke meters, and you fell for them hook line and sinker.
>>
>>
>
> No, I have actually seen a few blowups and the results of some others.
>
> Have you ever worked at a place that has lots of 480 volt 3 phase
> equipment ?

Yes.

> I did before retiring. One learns to respect what can hapen.

I've seen what happens when you connect two phases to one phase equipment, it's quite amusing.

And I don't respect things that will probably never happen.

[Commander Kinsey]

On Thu, 16 Jul 2020 21:13:11 +0100, Michael Terrell <terrell....@gmail.com> wrote:

> He is just an arc flash away from making an ash of himself.

I've done that actually, just scorched my hand for a couple of weeks.

[Commander Kinsey]

On Thu, 16 Jul 2020 18:54:08 +0100, Michael Terrell <terrell....@gmail.com> wrote:

> 208 is a standard three phase voltage. It is three 120 volt lines phased 120 degrees apart.

Ah, I didn't know that existed. I thought you only got 120 when you centre tapped a single 240. If you're gonna use three phase, wouldn't you want more voltage?

[Commander Kinsey]

Isn't that really hard to work out? We use cross sectional area in mm. Which is really easy to imagine. With the added bonus that a higher number is thicker. It's also pretty handy as a rough guide that 1 square mm carries 10 amps.

> and sheet metal.

Seriously? Wow. Why would you nbot measure a thickness in a unit of distance?

> We also use "guage"
> for measuring really thin stuff like plastic films. In the last case, it's
> a completly different unit, but with proper context won't confuse anybody.

We use microns.

> Question for the metric woodworkers. Does anybody cut a piece of wood to
> 317mm or 429mm or other off numbers when building a house or handing a
> door or installing a countertop?

Depends if something else is in the way. I'd always try to use round numbers.

[Ralph Mowery]

In article <op.0nvd9pimwdg98l@glass>, CFKi...@military.org.jp says...

>
> > He is just an arc flash away from making an ash of himself.
>
> I've done that actually, just scorched my hand for a couple of weeks.
>
>

If you had respected things that probably would never hapen, you would
not have scorched your hand.

[Jasen Betts]

sheet metal in mm (1.6mm, 0.65mm etc...)
plastic sheet in microns 40um etc.
electric wire in square mm.
fencing wire in mm diameter.

> Question for the metric woodworkers. Does anybody cut a piece of wood to
> 317mm or 429mm or other off numbers when building a house or handing a
> door or installing a countertop?

Yes, if that is the right size. buildings are usually specified in
multiples of 100mm. often multiples of 300mm or 1000mm
furniture usually in multiples of 25mm

Factory door sizes are 620mm + multiples of 50mm, but not all openings
are the right size for the factory door.

Timber sizes for dressed finger-jointed framing timber are accurate to
withion 0.5mm are are certain preferred multiples of 5mm eg: 70x35 used
mainly for non-structual walls. 90x45 used mainly for structural walls.

The stud spacing and top-plate height will typically be some multiple
of 50mm So a lot of the cutting for studs, and blocking is at multiples
of 5mm. that's if you're not using pre-fabricated framing.

Carpenters use millimeteres. they say centimeters
are for tailors, and inches are for cobblers.

--
Jasen.

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:

The separate amps jacks exist for at least two reasons:

1) If the range switch also switched in/out the current shunt, then the
user could accidentally create a short circult across the probe tips
simply by turning the range switch to or across the amps measurement
ranges. Even if they were quickly turning /across/ the amps settings
ranges, a brief short circuit would be created, which would cause
damage to the meter as well as the device under test depending upon
what was connected at the time.

2) By having the amps jacks separate, the range switch itself does not
have to have contacts beefy enough to carry the current for the amps
settings. Remember, when measuring amps, the current being measured
flows *through* the meter itself. This would require very different
(and likely much more expensive) range switch contacts.

Some meters do have sensors for the amps jacks that sound an alarm if
the probes are inserted in the amps jacks but the range switch is on a
different setting than amperes.

[Commander Kinsey]

On Fri, 17 Jul 2020 15:02:16 +0100, Rich <ri...@example.invalid> wrote:

> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>> On Fri, 03 Jul 2020 02:20:53 +0100, RheillyPhoull <Rhe...@bigslong.com> wrote:
>>
>>> On 2/07/2020 10:41 pm, Ralph Mowery wrote:
>>>> For a real scare you should see some of the safety movies that
>>>> Fluke put out. They show under test conditions what can hapen to
>>>> inexpensive meters and their meters under different conditions like
>>>> having the meter set for amps and putting across a 480 volt circuit
>>>> that has plenty of amps .
>>>>
>>> Ahh the old "Leaving it on amps" trick. How many of us can say they
>>> never did it ?
>>
>> I find it crazy that you can select volts and have the wires in the
>> amps holes. The switch should change the contacts. I've broken a
>> meter doing that, just measuring the voltage on a car battery. £100
>> meter, but UNFUSED FFS! At least the mA range was fused, but they
>> couldn't be bothered putting in a 20A fuse for the big range....
>
> The separate amps jacks exist for at least two reasons:
>
> 1) If the range switch also switched in/out the current shunt, then the
> user could accidentally create a short circult across the probe tips
> simply by turning the range switch to or across the amps measurement
> ranges. Even if they were quickly turning /across/ the amps settings
> ranges, a brief short circuit would be created, which would cause
> damage to the meter as well as the device under test depending upon
> what was connected at the time.

Then you put the amps ranges on one end of the dial. You would never go through them. And what idiot turns the dial while it's connected?!

> 2) By having the amps jacks separate, the range switch itself does not
> have to have contacts beefy enough to carry the current for the amps
> settings. Remember, when measuring amps, the current being measured
> flows *through* the meter itself. This would require very different
> (and likely much more expensive) range switch contacts.

Or a relay.

[Rich]

Some meters have range switches that rotate through a full 360 degrees
with no stops - there would be no "end of the dial" in those instances.

And even with an 'end of the dial' there is still the possibility of
landing 'off by one' while turning the dial.

> And what idiot turns the dial while it's connected?!

The same idiot who'd leave the leads plugged into the amps jacks and
then attempt to measure the voltage of a car battery (or some other low
impedance high current voltage source).

I suspect you would find changing the range switch while connected is
much more common than your response implies. Esp. for switching
up/down a range for meters that are not auto-ranging.

>> 2) By having the amps jacks separate, the range switch itself does not
>> have to have contacts beefy enough to carry the current for the amps
>> settings. Remember, when measuring amps, the current being measured
>> flows *through* the meter itself. This would require very different
>> (and likely much more expensive) range switch contacts.
>
> Or a relay.

Which also equates directly to added expense vs. having the user
themselves be that "relay". And for battery powered meters, shorter
battery life (due to the current consumed by the relay coil).

It is also possible (this is a guess in my part) that the CAT ratings
specify separate amps jacks for an added safety factor of "user must
deliberately move lead to obtain short circuit through meter".

As well, the user who'd leave the leads plugged into amps, and then try
to measure voltage on car battery or other high current source is also
just as likely to leave the range switch in the amps setting (after
having measured current somewhere) and subsequently try to measure
voltage. It is not possible to fully protect users who don't pay
attention from doing stupid things. Either they forget to unplug from
the amps jack, or they forget to switch away from the amps range,
either way they get a local fireworks display of their own doing.

[Commander Kinsey]

Then don't make them like that.

> And even with an 'end of the dial' there is still the possibility of
> landing 'off by one' while turning the dial.

Then have a gap which is connected to nothing.

>> And what idiot turns the dial while it's connected?!
>
> The same idiot who'd leave the leads plugged into the amps jacks and
> then attempt to measure the voltage of a car battery

Wrong. You adjust the dial to what you want to do, not remembering what you were measuring yesterday. Having only one thing to change makes it way easier to get it right.

> (or some other low impedance high current voltage source).

It only has to get over 20 amps to fuck the meter.

> I suspect you would find changing the range switch while connected is
> much more common than your response implies. Esp. for switching
> up/down a range for meters that are not auto-ranging.

Meters should always auto range. Mine all do, and I've never even considered adjusting the dial while it's connected. I'm not going to change between resistance, current, and volts and want to leave it connected to the same thing.

>>> 2) By having the amps jacks separate, the range switch itself does not
>>> have to have contacts beefy enough to carry the current for the amps
>>> settings. Remember, when measuring amps, the current being measured
>>> flows *through* the meter itself. This would require very different
>>> (and likely much more expensive) range switch contacts.
>>
>> Or a relay.
>
> Which also equates directly to added expense vs. having the user
> themselves be that "relay".

No, because you save on an extra socket.

> And for battery powered meters, shorter
> battery life (due to the current consumed by the relay coil).

Latching relays use very little indeed, like the one in my room thermostat. 2 AA batteries last years.

> It is also possible (this is a guess in my part) that the CAT ratings
> specify separate amps jacks for an added safety factor of "user must
> deliberately move lead to obtain short circuit through meter".

Then they're fools, because now "user can obtain short circuit by forgetting he was measuring current yesterday, or because a colleague was without him knowing". If it was selected on the dial, there is no possibility to make a mistake. You select what you want and that's what you get. It's illogical to have one thing pointing at volts while another thing is expecting current!

Anyway, a simple fuse would solve all this. All you lose if you make a mistake is a fuse, not the internal workings of the meter, the test leads, the thing you're testing, and possibly your face.

> As well, the user who'd leave the leads plugged into amps, and then try
> to measure voltage on car battery or other high current source is also
> just as likely to leave the range switch in the amps setting (after
> having measured current somewhere) and subsequently try to measure
> voltage.

Nope. I pick up a multimeter and set it to what I'm about to measure. Same way as I don't drive into my house because I left my car in forward gear yesterday.

> It is not possible to fully protect users who don't pay
> attention from doing stupid things. Either they forget to unplug from
> the amps jack, or they forget to switch away from the amps range,
> either way they get a local fireworks display of their own doing.

People make mistakes. The best equipment prevents this. My VW Golf for example would not allow me to select 1st gear when going 100mph. It was quite clever in fact. I could do that on purpose and it would drop one gear at a time to slow the car as quickly as possible to assist the brakes in an emergency. And yes I did try it a few times, one time I scared the shit out of the passenger (who had never seen an automatic gearbox before).

[Ralph Mowery]

In article <ret1h6$stk$1...@dont-email.me>, ri...@example.invalid says...

>
> I suspect you would find changing the range switch while connected is
> much more common than your response implies. Esp. for switching
> up/down a range for meters that are not auto-ranging.
>
> >> 2) By having the amps jacks separate, the range switch itself does not
> >> have to have contacts beefy enough to carry the current for the amps
> >> settings. Remember, when measuring amps, the current being measured
> >> flows *through* the meter itself. This would require very different
> >> (and likely much more expensive) range switch contacts.
> >
> > Or a relay.
>
> Which also equates directly to added expense vs. having the user
> themselves be that "relay". And for battery powered meters, shorter
> battery life (due to the current consumed by the relay coil).
>
> It is also possible (this is a guess in my part) that the CAT ratings
> specify separate amps jacks for an added safety factor of "user must
> deliberately move lead to obtain short circuit through meter".
>
> As well, the user who'd leave the leads plugged into amps, and then try
> to measure voltage on car battery or other high current source is also
> just as likely to leave the range switch in the amps setting (after
> having measured current somewhere) and subsequently try to measure
> voltage. It is not possible to fully protect users who don't pay
> attention from doing stupid things. Either they forget to unplug from
> the amps jack, or they forget to switch away from the amps range,
> either way they get a local fireworks display of their own doing.
>
>
>

I often leave the leads connected to a Simpson 260 and change voltage
ranges. Where I worked there were so many wires in a conduit carrring
120 VAC control voltage it was difficult to tell if the voltage was
'real' or induced by the coupling. I found out that if I started on the
500 volt range and then switched to the 250 volt range if the meter
pointer stayed in the same relative position I could then switch to the
50 volt range and the meter pointer would still be near the same
relative position if the voltage was induced. If the pointer changed
positions to follow the 120 VAC when going to the 250 volt scale the
voltage was real.

I doubt that the CAT rating requies seperate Amps positions for the
leads. Fluke uses special fuses in their meters to get the CAT ratings.
They do not have a seperate jack for the ohms settings either which is
more likely where the meter would be set. Most of the time the
circuit would have to be broken and the meter inserted to measuer amps.

As you say it is impossiable to fully protect everyone from doing
somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
dollar one goes a long ways.

I do have a Fluke test meter that is purty much fool proof up to 600
volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
wire through the prongs. It does have a switch for voltage and ohms. I
have on purpose set it to ohms and put it across a fuse in a 480 volt AC
circuit to see if the fuse is good or bad. No problem to do this.

[Commander Kinsey]

Better to use something that draws bit of current, like one of those screwdrivers that lights a neon through your capacitance.

> I doubt that the CAT rating requies seperate Amps positions for the
> leads. Fluke uses special fuses in their meters to get the CAT ratings.
> They do not have a seperate jack for the ohms settings either which is
> more likely where the meter would be set. Most of the time the
> circuit would have to be broken and the meter inserted to measuer amps.
>
> As you say it is impossiable to fully protect everyone from doing
> somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
> dollar one goes a long ways.
>
> I do have a Fluke test meter that is purty much fool proof up to 600
> volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
> wire through the prongs. It does have a switch for voltage and ohms. I
> have on purpose set it to ohms and put it across a fuse in a 480 volt AC
> circuit to see if the fuse is good or bad. No problem to do this.

With a bad fuse it doesn't blow up?

[Rich]

In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
> On Fri, 17 Jul 2020 21:26:15 +0100, Rich <ri...@example.invalid> wrote:
>> As well, the user who'd leave the leads plugged into amps, and then
>> try to measure voltage on car battery or other high current source
>> is also just as likely to leave the range switch in the amps setting
>> (after having measured current somewhere) and subsequently try to
>> measure voltage.
>
> Nope. I pick up a multimeter and set it to what I'm about to
> measure. Same way as I don't drive into my house because I left my
> car in forward gear yesterday.

Interesting....

Yet you said this yesterday:

From: "Commander Kinsey" <CFKi...@military.org.jp>
Date: Thu, 16 Jul 2020 20:09:20 +0100
Message-ID: <op.0nu3hup8wdg98l@glass>

...

I find it crazy that you can select volts and have the wires in the

amps holes. ... I've broken a meter doing that, just measuring the
voltage on a car battery. A £100 meter, but UNFUSED FFS!

...

One aspect of "set it to what I'm about to measure" should normally
include: "are the leads in the correct jacks".

[Ralph Mowery]

In article <op.0nw7h4ytwdg98l@glass>, CFKi...@military.org.jp says...

> I do have a Fluke test meter that is purty much fool proof up to 600
> > volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
> > wire through the prongs. It does have a switch for voltage and ohms. I
> > have on purpose set it to ohms and put it across a fuse in a 480 volt AC
> > circuit to see if the fuse is good or bad. No problem to do this.
>
> With a bad fuse it doesn't blow up?
>
>

No it does not . It is designed to protect its self from voltage on the
ohms scale. They are only about $ 130

Even better is a quick tester by Fluke. it has 2 leads and about 8 or
so leds on it. Both it and the T1000 look similar to bannanas, even
yellow in color. The 2nd tester is fully automatic. Connect the two
leads to anything under 600 or so volts. If voltage, the leds light up
, the more for more voltage. Anoter is for AC or DC. If there is less
than about 200 ohms and no voltage, there is a led and buzzer for that.

About as fool proof as they make it for quick tests.

[Commander Kinsey]

No, because it's illogical to change two things to set one thing.

[Commander Kinsey]

On Sat, 18 Jul 2020 00:10:49 +0100, Ralph Mowery <rmower...@earthlink.net> wrote:

> In article <op.0nw7h4ytwdg98l@glass>, CFKi...@military.org.jp says...
>> I do have a Fluke test meter that is purty much fool proof up to 600
>> > volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
>> > wire through the prongs. It does have a switch for voltage and ohms. I
>> > have on purpose set it to ohms and put it across a fuse in a 480 volt AC
>> > circuit to see if the fuse is good or bad. No problem to do this.
>>
>> With a bad fuse it doesn't blow up?
>>
>>
>
> No it does not . It is designed to protect its self from voltage on the
> ohms scale. They are only about $ 130

Howe does it measure ohms and distinguish its own current from the current from the circuit? That's if you're testing a DC circuit.

> Even better is a quick tester by Fluke. it has 2 leads and about 8 or
> so leds on it. Both it and the T1000 look similar to bannanas, even
> yellow in color. The 2nd tester is fully automatic. Connect the two
> leads to anything under 600 or so volts. If voltage, the leds light up
> , the more for more voltage. Anoter is for AC or DC. If there is less
> than about 200 ohms and no voltage, there is a led and buzzer for that.
>
> About as fool proof as they make it for quick tests.

Does it check for current if there's no voltage?

[Ralph Mowery]

In article <op.0nw7h4ytwdg98l@glass>, CFKi...@military.org.jp says...
>

> > I do have a Fluke test meter that is purty much fool proof up to 600
> > volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
> > wire through the prongs. It does have a switch for voltage and ohms. I
> > have on purpose set it to ohms and put it across a fuse in a 480 volt AC
> > circuit to see if the fuse is good or bad. No problem to do this.
>
> With a bad fuse it doesn't blow up?
>
>

No, it is designed to protect its self.

[Ralph Mowery]

In article <op.0nw9prwrwdg98l@glass>, CFKi...@military.org.jp says...

>
> > About as fool proof as they make it for quick tests.
>
> Does it check for current if there's no voltage?
>
>

Just how can there be curent if there is no voltage ?

There is no current by the leads, but works like a clamp on meter to
check for AC Current. Does not do DC current.

There can be voltage but no current.

[Commander Kinsey]

On Mon, 13 Jul 2020 21:04:07 +0100, Tom Gardner <spam...@blueyonder.co.uk> wrote:

> On 13/07/20 16:39, Jeroen Belleman wrote:
>> On 2020-07-13 17:27, Pimpom wrote:
>>> On 7/13/2020 6:06 PM, Commander Kinsey wrote:
>> [...]
>>>> If you're not American why did you say "my bad"? Your bad what? Finish the
>>>> sentence!
>>>>
>>> So now you're a grammar Nazi? This after I (and others) spent considerable
>>> time and effort[...]
>>
>> Just drop it. There are better things to do than to argue
>> with a cantankerous teenager. If a conversation turns into
>> a source of irritation, the best way is to simply drop out.
>
> Precisely.
>
> That was my decision too. An easy decision given the moniker
> "Commander Kinsey" is either someone that has too high a
> regard for themselves, or is indicating that they intend to
> troll.

No such thing as a troll, just someone you disagree with.

[Commander Kinsey]

On Mon, 13 Jul 2020 16:27:26 +0100, Pimpom <nob...@nowhere.com> wrote:

> On 7/13/2020 6:06 PM, Commander Kinsey wrote:

>> On Mon, 13 Jul 2020 05:53:29 +0100, Pimpom <nob...@nowhere.com> wrote:

>>
>>> On 7/13/2020 12:51 AM, Tom Gardner wrote:
>>>> On 12/07/20 19:01, Pimpom wrote:
>>>>> On 7/12/2020 11:15 PM, Commander Kinsey wrote:
>>>>>> On Fri, 26 Jun 2020 05:23:31 +0100, Cydrome Leader <pres...@mungepanix.com>
>>>>>> wrote:
>>>>>>
>>>>>>> In sci.electronics.equipment Pimpom <nob...@nowhere.com> wrote:
>>>>>
>>>>>>>> My mechanical slide caliper has a resolution of 0.001 inch. This
>>>>>>>> means that it can display measurements with a precision of 1 mil,
>>>>>>>
>>>>>>> What if your caliper had a resolution of 1 mil +/- 3 counts on the last
>>>>>>> digit?
>>>>> .....<snip>........
>>>>>>
>>>>>> In America, what is a "mill"? In the UK, it used to mean a thousandth of an
>>>>>> inch, but people use it to mean a millimetre nowadays.
>>>>>>
>>>>>
>>>>> It's not a mill. It's mil - single l. It means, and has always meant, a
>>>>> thousandth of an inch. It's not an Americanism.
>>>>
>>>> In the UK "mill" means millilitre.
>>>>
>>>> If you want to refer to fractions of an inch, then
>>>> it is /always/ "thou", i.e. thousandths of an inch.
>>>>
>>>> In the UK "mil/mill" /never/ means 0.001".
>>>>
>>>

>>> My bad. This is the first time I heard that the mil is not used
>>> as the unit for .001" in the UK. (I'm *not* an American).

>>
>> If you're not American why did you say "my bad"? Your bad what? Finish the sentence!
>>
> So now you're a grammar Nazi? This after I (and others) spent

> considerable time and effort patiently explaining to you a
> concept that many/most readers here probably already knew, and
> would quickly grasp if they didn't. Sheesh!
>
> And is there a law against non-Americans using an American
> expression? FYI I'm none of these: American, British, Australian
> or Canadian - or a citizen of any other country where English is
> natively spoken.

It's not grammar, it's missing off an entuire word, the one with the meaning in it!

It's like saying "Today I went out and did some".

[Cydrome Leader]

Not really. If you can only count with your fingers you probably aren't
building anything impressive to start with. The entire fallacy of "metric
is easy, base 10, duh" is just bullshit. Check dimensions of anything
designed by people that don't know what fractions are. There are tons of
weird numbers like 13.1mm and so forth. It's no different than 1-1/8th
inches.

>> and sheet metal.
>
> Seriously? Wow. Why would you nbot measure a thickness in a unit of distance?

The guage for sheet metal is sort of obnoxious. It will vary by type of
metal as well, if that makes any sense.

>> We also use "guage"
>> for measuring really thin stuff like plastic films. In the last case, it's
>> a completly different unit, but with proper context won't confuse anybody.
>
> We use microns.

how many microns thick is your plastic trash bag? The last ones I got were
speced on the box as "0.7 mil" There's no false sense of precision there,
like with the 610mm countertop or whatever it was.

>> Question for the metric woodworkers. Does anybody cut a piece of wood to
>> 317mm or 429mm or other off numbers when building a house or handing a
>> door or installing a countertop?
>
> Depends if something else is in the way. I'd always try to use round numbers.

Would round be 320mm and 430mm instead of 317 and 429? Do you split in 5mm
increments too? I'm really curious about this.

[Pimpom]

It took you more than a week to think up that comeback? Anyway,
good luck with your self-appointed job of reforming the usage of
American slang which, by the way, has pervaded much of the world
outside the US.

And what does "entuire" mean? Blimey! Skitt's Law, you know, old boy.

> It's like saying "Today I went out and did some".
>

That would be quite acceptable if the context were known.

[Cydrome Leader]

The simpson meters are interesting in that they have as many jacks as they
they positions on the switch. You really need to move the leads around all
the time to do anything. I guest it makes you think, a little. I did catch
myself reading the ohms range wrong though recently.

> I doubt that the CAT rating requies seperate Amps positions for the
> leads. Fluke uses special fuses in their meters to get the CAT ratings.
> They do not have a seperate jack for the ohms settings either which is
> more likely where the meter would be set. Most of the time the
> circuit would have to be broken and the meter inserted to measuer amps.
>
> As you say it is impossiable to fully protect everyone from doing
> somethen forgetful or stupid, but having a $ 300 meter instead of a $ 5
> dollar one goes a long ways.
>
> I do have a Fluke test meter that is purty much fool proof up to 600
> volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
> wire through the prongs. It does have a switch for voltage and ohms. I
> have on purpose set it to ohms and put it across a fuse in a 480 volt AC
> circuit to see if the fuse is good or bad. No problem to do this.

I just got one of those clamp current multimeters. I noticed some glaring
limitations vs the full out Fluke 87 V, but at the same time, it's way
more "idiot-proof".

The current ranges, even for DC at only available though the current
clamp. It's just not possible to short anything out with the test probes.
The downside (not really surprising) is no low current ranges. Ok fine.
The input impedance is pretty low at 1Meg as well, but for poking at line
voltage wiring, this is fine. Again, no matter what range you are set it,
it appears to be impossible to blow up the meter as it has no low
resistance across the leads modes. The ohms range seems to max out at 40k
or something surprisibly low like that, again, no big deal for prodding at
lighting circuits or an outlet, or some 24 volt circuit.

Getting all sorts of wonky reading with the banana jack type K
thermocouple though. It seems the meter has an internal thermometer and it
compares to the junction at the end of the probe. Not really sure how that
all works and how the temperatures of the banana jacks affect things as
they are not the special metals in the leads of the probe. I know with
normal process controllers, and deviation of the correct connector or
metals used will result in really strange readings.

[Cydrome Leader]

In sci.electronics.basics Ralph Mowery <rmower...@earthlink.net> wrote:

Hmm, Remeber those neon voltage testers with two leads and the bizarre
shirt pocket clip? I had one go out on me, showed no voltage when there
was some. Whoops.

Now I use one of those ground/wiring testers. I figure it will still light
up if one neon indicator fails.

[Ralph Mowery]

In article <rf8eq6$brr$1...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

> I do have a Fluke test meter that is purty much fool proof up to 600
> > volts and rated CAT 4. A T1000. It only measuers AC amps by passing a
> > wire through the prongs. It does have a switch for voltage and ohms. I
> > have on purpose set it to ohms and put it across a fuse in a 480 volt AC
> > circuit to see if the fuse is good or bad. No problem to do this.
>
> I just got one of those clamp current multimeters. I noticed some glaring
> limitations vs the full out Fluke 87 V, but at the same time, it's way
> more "idiot-proof".
>
> The current ranges, even for DC at only available though the current
> clamp. It's just not possible to short anything out with the test probes.
> The downside (not really surprising) is no low current ranges. Ok fine.
> The input impedance is pretty low at 1Meg as well, but for poking at line
> voltage wiring, this is fine. Again, no matter what range you are set it,
> it appears to be impossible to blow up the meter as it has no low
> resistance across the leads modes. The ohms range seems to max out at 40k
> or something surprisibly low like that, again, no big deal for prodding at
> lighting circuits or an outlet, or some 24 volt circuit.
>
>

Meters like the T1000 are for quick go or no go test mainly. For what
they are mainly used for it does not make any differnece if they are off
by even 10 %. For quick tests in an industrial enviroment it does not
matter if the control voltage is 115.25 volts when anything from around
110 to 130 volts is close enough. Most circuits will have less than
1000 ohms resistance , many of the motors will show up as an almoat
short if the windings are good. Fuses are almost shorts or opens.

The Fluke 87 and meters like that are more for electronic tests. The
specs on them are very good and will be accurate to one or two decimal
places.

When I worked I had access to almost any kind of meter or test set. I
often grabbed my Simpson 260 and analog Ampprobe for the equipment that
would not start or run. However I would stick the Fluke 'Bananna' in my
pocket to check some things like the fuses in a power circuit.

For the instruments where they needed to be measured to less than 1 %
out came the fluke 87 or more likely a special piece of equipment that
has a Heart interface. That reads signals on the instrument lines.

[Ralph Mowery]

In article <rf8f20$brr$2...@reader1.panix.com>, pres...@MUNGEpanix.com
says...

>
> Hmm, Remeber those neon voltage testers with two leads and the bizarre
> shirt pocket clip? I had one go out on me, showed no voltage when there
> was some. Whoops.
>
> Now I use one of those ground/wiring testers. I figure it will still light
> up if one neon indicator fails.
>
>
>

Yes, I used one very often. One learns to put the leads across a source
that should have voltage on it to see if the neon bulb lights up, then
put it to the point to test and if the neon does not light up, go back
to a point that should have voltage on it.


Bad thing about where I worked there was so many wires in conduit that
the neon would light up even if there was no 'real' voltage on the wire.
Just induced voltage that if put under much of a load at all will seem
to diaspear.
It is still enough to shock the crap out of you, especially if wet with
sweat.

[Commander Kinsey]

You miss the point, it's not the end of the world.

[Rich]

A scorched hand, no, not the end of the world.

A stopped heart, which *can* happen if the arc flash conducts enough
current through the wrong part of the body, well then for the one who's
heart just got stopped it might just be the end of the world.

[Commander Kinsey]

It seldom travels that path.

[Cydrome Leader]

In sci.electronics.basics Commander Kinsey <CFKi...@military.org.jp> wrote:
> On Thu, 02 Jul 2020 06:45:42 +0100, Cydrome Leader <pres...@mungepanix.com> wrote:
>
>> In sci.electronics.equipment Ralph Mowery <rmower...@earthlink.net> wrote:
>>> In article <rdecuc$m73$1...@reader1.panix.com>, pres...@MUNGEpanix.com
>>> says...
>>>>
>>>> > So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?
>>>>
>>>> might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
>>>> have been from a raffle or something like that.
>>>>
>>>> The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
>>>> AC ranges which are "1.2% RDG +10 Digits". If I had new leads, I'd trust it
>>>> with outlet voltage, but would stay away from 208volts. The meter has 3.5
>>>> digits or max display of 1999. I'm figuring a real 100volt AC reading could
>>>> be 99 to 101 plus another error of +/- 1 volt for the 10 digits tolerance
>>>> on the display or count. so 100volts from your Japanese outlet reference
>>>> might read 98 to 102 volts. So while in the ballpark, it's better than you
>>>> can read off a Simpson 260 meter in the AC voltage range. I could be wrong
>>>> on this too.
>>>>
>>>> It's a pretty decent meter for poking at DC circuits for the tens of
>>>> dollars is must have cost when new.
>>>>
>>>>
>>>
>>> It seems that maybe due to modern manufactoring the meters are more
>>> accurate than they were 20 years ago. I bought some DC voltmeters from
>>> China. They display 3 digits. They read from 0 to 99.9 volts. I coulg
>>> get 4 of them for less than $ 15 including the shipping. I hooked all 4
>>> of them in parallel with a Fluke 87 . Three of them tracked right along
>>> with the Fluke with the last digit sometimes being one high or low from
>>> 0 to 24 volts. The fourth one was off by an average of 2 on the last
>>> digit. I found an adjustment screw on the back of the meter and tweaked
>>> it and re ran the test. It then fell in line with the other meters.
>>
>> Have you run this test with AC? That seems to be where the wheels come
>> off. I brought up this thread to a friend and he mentioned his quest to
>> repair some sort of HP true RMS meter that uses a thermocouple and heater
>> to properly measure complex waveforms. I can't even guess how slow such a
>> meter might be.
>
> How well do these things work measuring dodgy waves like from a cheap UPS or invertor?

Probably perfectly.

>>> I had 3 or 4 of the Harbor Freight 'free' multimeters. The ones that
>>> usually sell for around $ 5. They seem to be reasonable accurate for
>>> the money. Plenty accurate for the home user to test things around the
>>> house. I do admit that the safety issue of putting them across the 120
>>> or 240 volt power wires is somewhat doubtful. I sure would not use one
>>> where I worked to put across the 480 volt 3 phase system that is fused
>>> with 200 amps.
>>
>> I'm pretty timid with anything upstream from a plain outlet.
>
> I've replaced outlets (240V, not the namby pamby USA stuff) without
> turning off the power - other outlets on the same circuit were being
> used in the office and I saw no point in interrupting them.

cool story.

> Just keep your fingers off the metal things and don't short stuff together. Wear goggles and gloves if you want to be a girl about it.
>
>> I had an
>> edison base fuse burst in my hand once. Never seen one come apart before.
>> It was just a 120v lighting circuit, but right off the service panel.
>> There's way more excitement near those things.
>
> Try shorting two phases together with 500A cables. That causes lots of
> smoke, a fire alarm, 3 fire engines, and a visit from the power company.
> Do not ever employ Irish electricians.

In America we have fuses and circuit breakers. Check youtube for a video
about how they work.

[Cydrome Leader]

In sci.electronics.basics Commander Kinsey <CFKi...@military.org.jp> wrote:

> On Tue, 30 Jun 2020 04:52:44 +0100, Cydrome Leader <pres...@mungepanix.com> wrote:
>
>> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>>> On Wed, 24 Jun 2020 21:06:04 +0100, Rich <ri...@example.invalid> wrote:
>>>
>>>> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:
>>>>> On Thu, 18 Jun 2020 15:38:46 +0100, Pimpom <nob...@nowhere.com> wrote:
>>>>>
>>>>>> On 6/18/2020 6:33 PM, Commander Kinsey wrote:
>>>>>>> I just bought an amp clamp meter, and it states the error is "+/-
>>>>>>> 1.9% + 3 digits". What does the "3 digits" part mean?
>>>>>>>
>>>>>>
>>>>>> If your meter should read, say 1.875 A, the correct reading could
>>>>>> be anywhere from 1.872 to 1.878. This is a possible error in the
>>>>>> display presented to you in the analog-digital display conversion
>>>>>> process. The +/-1.9% possible error is about the measurement
>>>>>> taken including - but not only - any error made by the sensor.
>>>>>
>>>>> Thanks, I wonder why all my other meters only list a % error. Is it
>>>>> included within it somehow, or are they just lying, or do some meters
>>>>> not have this error?
>>>>
>>>> One generally finds the percentage plus digits error measures on more
>>>> expensive equipment. Less expensive equipment more often than not only
>>>> lists a percentage and nothing more.

>>>
>>> So should I assume the cheaper ones are lying? Or have they just made a rough estimate adding the two errors?
>>
>> might be both. I dug out my first DMM, a Wavetek DM2, circa 1990s. It might
>> have been from a raffle or something like that.
>>
>> The DC voltage specs range from 0.8% +1 digit (not bad really) over to the
>> AC ranges which are "1.2% RDG +10 Digits".
>

> TEN!? Surely that's more than the number of digits it has? In which case it has no accuracy at all.

I'm pretty sure they mean 10 counts which could be 1 volt on a scale with
1 decimal place. That does sound terrible if there were no decimal places
though.

>> If I had new leads, I'd trust it
>> with outlet voltage, but would stay away from 208volts.
>

> You oughta complain about that low voltage. Some equipment needs at
> least 220.

terribly designed equiment, maybe. 208 is standard voltage for phase to
phase in a three wire systems, as used in a commercial setting in the US.

minilabs, for processing 35mm film fall into the stupid design category,
usually being speced for 120 or 240 at dozens of amps.

Nobody runs a fucking minilab in their home, and it makes no sense to run
30+amp 120volt service anyways. So, in any place that would have a
minilab, they're going to have 208, not 120 or 240. So the result is boost
transformer has to be installed. They're not large, being rated only for
the KVA of the voltage boost, but it's still dumb.

It's just shitty lazy design, where maybe they can strap two heating
elements in series for 240 and parallel them for 120, but again, nobody
uses machines like that in their home where split phase power is available
anyways.

The better designed machines won't have resisitve heating elements that
burn out at 240 and still have motors that will start and run fine on 208.

[Commander Kinsey]

On Fri, 17 Jul 2020 13:15:24 +0100, Jasen Betts <ja...@xnet.co.nz> wrote:

> On 2020-07-16, Cydrome Leader <pres...@MUNGEpanix.com> wrote:
>> In sci.electronics.equipment Commander Kinsey <CFKi...@military.org.jp> wrote:

>>> On Sun, 12 Jul 2020 20:21:10 +0100, Tom Gardner <spam...@blueyonder.co.uk> wrote:
>>>
>>>> On 12/07/20 19:01, Pimpom wrote:
>>>>> On 7/12/2020 11:15 PM, Commander Kinsey wrote:

>>>>>> On Fri, 26 Jun 2020 05:23:31 +0100, Cydrome Leader <pres...@mungepanix.com>
>>>>>> wrote:
>>>>>>
>>>>>>> In sci.electronics.equipment Pimpom <nob...@nowhere.com> wrote:
>>>>>
>>>>>>>> My mechanical slide caliper has a resolution of 0.001 inch. This
>>>>>>>> means that it can display measurements with a precision of 1 mil,
>>>>>>>
>>>>>>> What if your caliper had a resolution of 1 mil +/- 3 counts on the last
>>>>>>> digit?
>>>>> .....<snip>........
>>>>>>
>>>>>> In America, what is a "mill"? In the UK, it used to mean a thousandth of an
>>>>>> inch, but people use it to mean a millimetre nowadays.
>>>>>>
>>>>>
>>>>> It's not a mill. It's mil - single l. It means, and has always meant, a
>>>>> thousandth of an inch. It's not an Americanism.
>>>>
>>>> In the UK "mill" means millilitre.
>>>>
>>>> If you want to refer to fractions of an inch, then
>>>> it is /always/ "thou", i.e. thousandths of an inch.
>>>>
>>>> In the UK "mil/mill" /never/ means 0.001".
>>>
>>> Yes it does. My neighbour's a tradesman (in Scotland) and says
>>> "mill/mil" (I don't know which as they sound the same in speech) as
>>> shorthand for millimetre. As in "that kitchen unit is 600 mill wide".
>>> Since we don't use inches for such things in the UK, there's no
>>> confusion.
>>
>> The context there is key too. While I'd not measure a countertop or
>> whatever in millimeters, it would make no sense that anything in a kitchen
>> would be measured thicknesses of paper.
>>

>> We (in the US) use "guage" for wire and sheet metal. We also use "guage"

>> for measuring really thin stuff like plastic films. In the last case, it's
>> a completly different unit, but with proper context won't confuse anybody.
>

> sheet metal in mm (1.6mm, 0.65mm etc...)
> plastic sheet in microns 40um etc.
> electric wire in square mm.
> fencing wire in mm diameter.

Much more sensible. Guage is meaningless and is the wrong way round, higher numbers are smaller!

>> Question for the metric woodworkers. Does anybody cut a piece of wood to
>> 317mm or 429mm or other off numbers when building a house or handing a
>> door or installing a countertop?
>

> Yes, if that is the right size. buildings are usually specified in
> multiples of 100mm. often multiples of 300mm or 1000mm
> furniture usually in multiples of 25mm
>
> Factory door sizes are 620mm + multiples of 50mm, but not all openings
> are the right size for the factory door.

There seems to be no standard for doors. You can order about 15 different sizes in the UK, but never anywhere near the one you need.

> Timber sizes for dressed finger-jointed framing timber are accurate to
> withion 0.5mm are are certain preferred multiples of 5mm eg: 70x35 used
> mainly for non-structual walls. 90x45 used mainly for structural walls.
>
> The stud spacing and top-plate height will typically be some multiple
> of 50mm So a lot of the cutting for studs, and blocking is at multiples
> of 5mm. that's if you're not using pre-fabricated framing.
>
> Carpenters use millimeteres. they say centimeters
> are for tailors, and inches are for cobblers.

I use the most sensible denomination for the job. I won't say 600mm when I could say 60cm. And I weigh myself in stone, not pounds.

[Commander Kinsey]

I meant does it automatically work out if you want to test for current or voltage?

[Commander Kinsey]

On Tue, 21 Jul 2020 07:35:18 +0100, Pimpom <nob...@nowhere.com> wrote:

> On 7/21/2020 2:06 AM, Commander Kinsey wrote:
>> On Mon, 13 Jul 2020 16:27:26 +0100, Pimpom <nob...@nowhere.com> wrote:
>>
>>> On 7/13/2020 6:06 PM, Commander Kinsey wrote:
>>>> On Mon, 13 Jul 2020 05:53:29 +0100, Pimpom <nob...@nowhere.com> wrote:
>>>>
>>>>>
>>>>> My bad. This is the first time I heard that the mil is not used
>>>>> as the unit for .001" in the UK. (I'm *not* an American).
>>>>
>>>> If you're not American why did you say "my bad"? Your bad what? Finish the sentence!
>>>>
>>> So now you're a grammar Nazi? This after I (and others) spent
>>> considerable time and effort patiently explaining to you a
>>> concept that many/most readers here probably already knew, and
>>> would quickly grasp if they didn't. Sheesh!
>>>
>>> And is there a law against non-Americans using an American
>>> expression? FYI I'm none of these: American, British, Australian
>>> or Canadian - or a citizen of any other country where English is
>>> natively spoken.
>>
>> It's not grammar, it's missing off an entuire word, the one with the meaning in it!
>>
> It took you more than a week to think up that comeback?

You think all I do is reply in here?

> Anyway, good luck with your self-appointed job of reforming the usage of
> American slang which, by the way, has pervaded much of the world
> outside the US.

It's not said in the UK. We can speak our own language correctly.

> And what does "entuire" mean? Blimey! Skitt's Law, you know, old boy.

Learn the difference between a typo and stupidity.

>> It's like saying "Today I went out and did some".
>>
> That would be quite acceptable if the context were known.

Why make your conversations like jpeg encoding?