What is the best way to get 1.34 volts, low current to replace Hg Batt
tm
I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
ideas?
It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
volt LiIon battery.
Regards,
Tom
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Jan Panteltje
<the_ob...@whitehouse.gov> wrote in <i6gdlm$1lp7$1...@adenine.netfront.net>:
The dropout voltage of a LM317 is between 1.25 V at 100 °C,
and 1.75 V at -50 °C, at 50 mA.
So that would do.
Some trimpot to set the 1.34 V.
Tim Williams
news:i6giih$lqd$1...@news.albasani.net...
>>I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer.
>>Any
>>ideas?
>>
>>It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
>>volt LiIon battery.
>
> and 1.75 V at -50 °C, at 50 mA.
> So that would do.
> Some trimpot to set the 1.34 V.
The tempco is probably lower, too...
You won't get any bonus points for leakage though. LM317 is 1mA or
something, so your LiIon will bleed down fairly quickly (~weeks?).
There are precision low current references that run at microamperes. If
you can find an adjustable one, you can get what you need. Else, use a
CMOS op-amp and large divider resistors to set gain.
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
k...@att.bizzzzzzzzzzzz
>Hi,
>
>I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
>ideas?
>
>It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
>volt LiIon battery.
A couple of years ago I bought a couple of Hg battery replacements for
cameras. Basically they're the size of the original battery and take a 1.5V
buttons cell, with an LDO of some sort to drop the voltage appropriately. I
don't remember the specifics.
John Larkin
<the_ob...@whitehouse.gov> wrote:
>Hi,
>
>I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
>ideas?
>
>It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
>volt LiIon battery.
>
>
>Regards,
>Tom
Will it be running continuously? Then you might use one of those
micropower voltage regulator chips, LT3008 or something like that.
John
Jim Yanik
news:i6gdlm$1lp7$1...@adenine.netfront.net:
> Hi,
>
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer.
> Any ideas?
>
> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a
> 3.6 volt LiIon battery.
>
>
> Regards,
> Tom
why not keep it simple and run it from a pair of AA alkaline cells?
No need to recharge,no expensive batteries.
--
Jim Yanik
jyanik
at
localnet
dot com
Fred McKenzie
"k...@att.bizzzzzzzzzzzz" <k...@att.bizzzzzzzzzzzz> wrote:
That may be the "MR-9 battery adapter", although there may have been
others available. A Google search found it. One source appears to be:
<http://www.criscam.com/mercury_battery_adapters.php>
I don't know if the MR-9 will meet Tom's needs. It uses a 386 silver
oxide cell.
Fred
bw
"tm" <the_ob...@whitehouse.gov> wrote in message
news:i6gdlm$1lp7$1...@adenine.netfront.net...
> Hi,
>
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
> ideas?
>
> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
> volt LiIon battery.
>
http://www.myoldcamera.com/Wein%20Cell%20Page%203.25.06.html
whit3rd
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
> ideas?
Sure. Buy another mercury battery. They have much lower noise than
semiconductor regulators, better output stability than other battery
types, and some (small) types are still available, last time I heard,
for compatibility with old gear.
An alkaline battery can make a nice 0.5 Hz triangle wave generator,
because there's a gas discharge and venting occurs. If you really
want to
get the precision, accuracy, and low impedance of a mercury battery,
resign yourself to paying for proper disposal.
k...@att.bizzzzzzzzzzzz
Yep, that's it. The PX625 was what I needed to emulate (Canon camera).
tm
<k...@att.bizzzzzzzzzzzz> wrote in message
news:a3ho86dp90tjf93dq...@4ax.com...
I did see that one plus one like it in England for about $35 or so that was
for the PX-1.
The cell is just used for the Ohms measurements and is switched off when not
in use.
Anyway, thanks guys for the suggestions.
tm
Winston
> Hi,
>
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
> ideas?
>
> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
> volt LiIon battery.
Why not use a zinc-air cell?
Compare the discharge curves on page 3:
http://olympus.dementia.org/Hardware/PDFs/batt-adapt-US.pdf
--Winston
Dennis
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
> ideas?
> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
> volt LiIon battery.
> Regards,
> Tom
Just out of interest, these guys sell a drop in voltage reducing adaptor to
do what you want:
http://www.smallbattery.company.org.uk/sbc_mr50_adapter.htm
k...@att.bizzzzzzzzzzzz
>On 9/11/2010 10:23 AM, tm wrote:
>> Hi,
>>
>> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
>> ideas?
>>
>> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
>> volt LiIon battery.
>
>Why not use a zinc-air cell?
AIUI, they have a very poor shelf life and are quite expensive, given the
shelf life.
whit3rd
> On 9/11/2010 10:23 AM, tm wrote:
> > I need to replace a mercury PX-1 cell
> Why not use a zinc-air cell?
Zinc-air cells are oxygen pressure sensitive.
Every breeze or exhaled breath will wiggle the needle
on the meter.
Winston
At what time constant?
I see that it takes from 1 to 3 minutes for the battery
to begin converting power after one removes the tab.
Is it possible that tiny momentary variations in
oxygen concentration would 'average out' acceptably?
My Google-fu wasn't up to the task of answering that question.
--Winston
--
I pride myself on my unimportance.
(One must excel at something, or what
is a Heaven for?)
Nik
>
Thank you. That's a link worth saving.
FWIW, I was looking at an old Babani book recently where it calibrates a
741 op-amp boosted analogue meter against a 'common or garden' mercury
'deaf aid' cell.
;-)
---------------------------------------
Posted through http://www.Electronics-Related.com
whit3rd
> On 9/12/2010 2:35 PM, whit3rd wrote:
> > Zinc-air cells are oxygen pressure sensitive.
> > Every breeze or exhaled breath will wiggle the needle
> > on the meter.
>
> At what time constant?
>
> I see that it takes from 1 to 3 minutes for the battery
> to begin converting power after one removes the tab.
For a nearby bunch of people breathing out diminished O2,
it'll be a few minutes (for diffusion). For a wind gust that lowers
the local air pressure, only a few milliseconds. And for
local barometric changes, there will be corresponding shifts
in the average output voltage from day to day.
Heaven only knows what effect ozone or laboratory gasses
might have.
If the requirement is just for a stable reference voltage, there
are stabilized ICs that can handle the task. If you need low noise,
and low output impedance at a broad frequency range, and
good voltage stability, it's hard to beat a mercury cell, even
just the 'regular' ones, not the Weston cells.
The camera-battery solutions are not reference-grade sources.
Nik
Winston
> Sorry, link& site...
Try again?
Works for me.
Robert Baer
she got in de way..
Martin Brown
> On 9/12/2010 2:35 PM, whit3rd wrote:
>> On Sep 11, 9:53 pm, Winston<Wins...@bigbrother.net> wrote:
>>> On 9/11/2010 10:23 AM, tm wrote:
>>
>>>> I need to replace a mercury PX-1 cell
>>
>>> Why not use a zinc-air cell?
>>
>>
>> Zinc-air cells are oxygen pressure sensitive.
>> Every breeze or exhaled breath will wiggle the needle
>> on the meter.
>
>
> At what time constant?
>
> I see that it takes from 1 to 3 minutes for the battery
> to begin converting power after one removes the tab.
>
> Is it possible that tiny momentary variations in
> oxygen concentration would 'average out' acceptably?
I expect so. More worrying would be the day to day variations with
prevailing atmospheric pressure. But I expect a zinc air cell might just
about be OK given that photographers use them in vintage light meters. eg
http://www.ihagee.org/batt-adapt-us.pdf
Their other suggestion is Schottky diode in series with a silver-oxide
cells but then you would have to worry about temperature coefficients.
>
> My Google-fu wasn't up to the task of answering that question.
Duracell have a reasonably nice treatment of these batteries, but you
cannot get to it through their new improved Flashy website that takes
aeons to load even on a T1 broadband connection.
http://www1.duracell.com/oem/Primary/Zinc/Zinc_Air_Tech_Bulletin.pdf
I honestly doubt that oxygen starvation will be a problem for a zinc air
cell being used as a reference voltage at very low currents unless the
battery chamber is hermetically sealed.
Although mercury cells are banned for consumer gear are you certain that
the required spare mercury cell or an approved functional equivalent is
not available through Keithley (for a price).
Regards,
Martin Brown
Jim Yanik
news:9dCdneyxhrN9dAzR...@posted.localnet:
as if an ordinary mercury battery was "reference-grade"....
> The pisser is that mercury cells are impossible to find..Poly-Ticks,
> she got in de way..
>
I'm surprised that no IC manufacturer has designed a chip to do this with
today's available 1.5v or 3v cells,or that some entreprenure hasn't made a
tiny SMD circuit board to do it.
Google turned up this site;
http://www.techlib.com/electronics/mercury.htm
Jim Thompson
wrote:
Probably so significant market.
...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
The Ground Zero Mosque IS Appropriate When Renamed...
The Obama Monument to American Impotence
Winston
> On 13/09/2010 20:53, Winston wrote:
>> On 9/12/2010 2:35 PM, whit3rd wrote:
>>> On Sep 11, 9:53 pm, Winston<Wins...@bigbrother.net> wrote:
>>>> On 9/11/2010 10:23 AM, tm wrote:
>>>
>>>>> I need to replace a mercury PX-1 cell
>>>
>>>> Why not use a zinc-air cell?
>>>
>>>
>>> Zinc-air cells are oxygen pressure sensitive.
>>> Every breeze or exhaled breath will wiggle the needle
>>> on the meter.
>>
>>
>> At what time constant?
>>
>> I see that it takes from 1 to 3 minutes for the battery
>> to begin converting power after one removes the tab.
>>
>> Is it possible that tiny momentary variations in
>> oxygen concentration would 'average out' acceptably?
>
> I expect so. More worrying would be the day to day variations with prevailing atmospheric pressure. But I expect a zinc air cell might just about be OK given that photographers use them in vintage light meters. eg
>
> http://www.ihagee.org/batt-adapt-us.pdf
>
> Their other suggestion is Schottky diode in series with a silver-oxide cells but then you would have to worry about temperature coefficients.
I expect that we could analyze this closely enough to determine that the
original mercury cell wasn't ever *really* the perfect component, either.
:)
>> My Google-fu wasn't up to the task of answering that question.
>
> Duracell have a reasonably nice treatment of these batteries, but you cannot get to it through their new improved Flashy website that takes aeons to load even on a T1 broadband connection.
>
> http://www1.duracell.com/oem/Primary/Zinc/Zinc_Air_Tech_Bulletin.pdf
>
> I honestly doubt that oxygen starvation will be a problem for a zinc air cell being used as a reference voltage at very low currents unless the battery chamber is hermetically sealed.
>
> Although mercury cells are banned for consumer gear are you certain that the required spare mercury cell or an approved functional equivalent is not available through Keithley (for a price).
That is a good question for the OP.
Thanks for the info, Martin.
tm
"Winston" <Win...@bigbrother.net> wrote in message
news:i6to7...@news6.newsguy.com...
OP here,
It turns out Keithley does have a fix for using a standard AA cell. It
involves changing
three resistor values, two of which are very difficult to get to. Plus, I am
not sure if the
standard AA cell is as stable as the Hg cell was. This cell provides the
drive for the
ohms measurement.
Thanks to all for the ideas. I still may consider making a power supply for
this. The meter
has three power supplies made up from industrial 9 volt batteries. It has
+/- 18 volts, +/- 9
volts, and the Hg 1.34 volt. All of these are independent and do not share a
common ground.
Regards,
tm
Maybe a small switcher with three windings and independent common points
might be a consideration.
Rich Grise
>
> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
> ideas?
>
> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
> volt LiIon battery.
Why not just design a small precision regulator?
Thanks,
Rich
Michael A. Terrell
How are you going to keep it from running the battery down when it
isn't needed?
--
Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.
Martin Brown
>
> Rich Grise wrote:
>>
>> On Sat, 11 Sep 2010 13:23:18 -0400, tm wrote:
>>>
>>> I need to replace a mercury PX-1 cell in a Keithley 802 Electrometer. Any
>>> ideas?
>>>
>>> It is 1.34 volts +/- 0.02 volts. Ideally, something that runs from a 3.6
>>> volt LiIon battery.
>>
>> Why not just design a small precision regulator?
>
>
> How are you going to keep it from running the battery down when it
> isn't needed?
Looks like ON Semi already have one that could do the job:
http://www.onsemi.com/pub_link/Collateral/MC78LC00-D.PDF
Most batteries can stand 1uA loads for almost as long as their nominal
shelf life - and some will live longer as a result. Tempco is nothing to
write home about though.
Regards,
Martin Brown