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bizarre temp controller behavior
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Cydrome Leader
Apr 15, 2013, 4:02:01 PM4/15/13
to
I've been working on a large C-41 film developing machine that has vats of
chemicals which must be held at exact temperates of 100F.
Each tank had 100 ohm platinum junction probes and the controllers are the
digiwheel style Omron E5CS-somethingsomething units.
Most have failed and other methods are used to maintain chemistry
temperature, but the critical one for developer is acting strange.
We got a new probe for it, a two lead Pt probe and wired it up into the
cable harness going back to the controller of the machine using the
original three leads.
When exposed to air the proble and Omron unit work fine. If you warm it
with your hand, it works fine. If you dip it in a jug of any liquid it
measures the temp corrected.
If the probe goes into any part of the developer, the temp reads as out of
range (39.9C or around 106F).
Ok, maybe it's electrical leakage. Putting the probe in an electrically
insulated sheath doesn't work either. Temps go out of limits or read
really high.
Ok, maybe the probe isn't grounded, or there's a weird electrical leakage
issue, so I ground the probe to the original thermistor shield. No dice,
temps our of range.
I even attached a lead to the metal probe and dumped it into the developer
tank to see if it's electrical noise or leakage. No problems with temp
readings in air or liquid if the probe housing is wired to the developer
tank.
It just never works when immersed, which is baffling.
I tried the other "spare" controllers and they all seem to behave the same
way, or are just dead. Tried other new probes, they all behave the same
way too. They all measure 107ish ohms at room temp and the controllers are
the correct ones for platinum probes.
The only and next move is just replace the temp controller. The omron
stuff has crappy docs (good luck finding old data sheets) and is overly
complex, so I'm steering towards something from Panasonic. No crazy
hysteresis loops or fuzzy logic are needed. If the heater has to cycle
every 10 seconds, that's fine as the racks going in an out of the tanks
can shock the temperatures, and fast recovery is needed.
The machine itself has no docs, is no longer made and there are no
original parts available. Having custom parts made for these things is
becoming the norm, and pretty expensive. The original probes were sealed
in plastic tubes, but the reason why isn't known. There are no spares of
even duds left to take apart. I tried replacing the cable of about 10 feet
between the controller and probe, but it behaved about the same way but
still registered a temp too high.
Has anybody come across something this strange, or know what may be
causing it?
chemicals which must be held at exact temperates of 100F.
Each tank had 100 ohm platinum junction probes and the controllers are the
digiwheel style Omron E5CS-somethingsomething units.
Most have failed and other methods are used to maintain chemistry
temperature, but the critical one for developer is acting strange.
We got a new probe for it, a two lead Pt probe and wired it up into the
cable harness going back to the controller of the machine using the
original three leads.
When exposed to air the proble and Omron unit work fine. If you warm it
with your hand, it works fine. If you dip it in a jug of any liquid it
measures the temp corrected.
If the probe goes into any part of the developer, the temp reads as out of
range (39.9C or around 106F).
Ok, maybe it's electrical leakage. Putting the probe in an electrically
insulated sheath doesn't work either. Temps go out of limits or read
really high.
Ok, maybe the probe isn't grounded, or there's a weird electrical leakage
issue, so I ground the probe to the original thermistor shield. No dice,
temps our of range.
I even attached a lead to the metal probe and dumped it into the developer
tank to see if it's electrical noise or leakage. No problems with temp
readings in air or liquid if the probe housing is wired to the developer
tank.
It just never works when immersed, which is baffling.
I tried the other "spare" controllers and they all seem to behave the same
way, or are just dead. Tried other new probes, they all behave the same
way too. They all measure 107ish ohms at room temp and the controllers are
the correct ones for platinum probes.
The only and next move is just replace the temp controller. The omron
stuff has crappy docs (good luck finding old data sheets) and is overly
complex, so I'm steering towards something from Panasonic. No crazy
hysteresis loops or fuzzy logic are needed. If the heater has to cycle
every 10 seconds, that's fine as the racks going in an out of the tanks
can shock the temperatures, and fast recovery is needed.
The machine itself has no docs, is no longer made and there are no
original parts available. Having custom parts made for these things is
becoming the norm, and pretty expensive. The original probes were sealed
in plastic tubes, but the reason why isn't known. There are no spares of
even duds left to take apart. I tried replacing the cable of about 10 feet
between the controller and probe, but it behaved about the same way but
still registered a temp too high.
Has anybody come across something this strange, or know what may be
causing it?
anorton
Apr 15, 2013, 5:41:30 PM4/15/13
to
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
news:kkhmbp$r14$1...@reader1.panix.com...
strongly absorbed by the solution. If the tank walls are nice and shiny it
might bounce around until absorbed by the probe. Take a sample out of the
vat and immediately measure it. Wrap the probe with insulator and then
aluminum foil and see if the reading is more accurate. The tank walls
might even focus the IR at some particular point.
Gunner Asch
Apr 15, 2013, 6:47:26 PM4/15/13
to
Sometimes screwing the unscrutable is a pain in the ass..so find a
work around to make it work....is much simpler
Gunner
>
>
Cydrome Leader
Apr 15, 2013, 6:49:34 PM4/15/13
to
tank itself is some sort of grey plastic. There's a compartment off to
the side where the probe usually sits, which is connected to a filter and
recirculator pump which is always on. The heater is one of those flow
through units attached with hoses to the main tank, pump and well which
has the filter cartridge.
The probe reads high temps anywhere inside the main tank or the small one
off to the side, so it doesn't seem like it's getting blasted with the
output of the heater, I'm not dunking my arm in there to feel where the
currents are though.
I'll try the insulator/foil experiment. The probe itself is some sort of
stainless, I have no idea how it reacts to IR. The plastic sheath I tried
before was just a piece of black PVC with one end heat sealed.
Spehro Pefhany
Apr 15, 2013, 7:04:54 PM4/15/13
to
room temperature, but okay..
There are other types of RTDs.. but the old "US Standard" alpha =
0.00392 is not very much different from the DIN standard at 40C (less
than 1 degree C). The old J Pt100 Japanese standard was similar to the
obsolete US standard. Everyone uses the Euro standard now, pretty
much.
What you are saying does not make a lot of sense. What is the
temperature of the developer? 100F is 37.8C, so very close to what you
say is the upper limit of the controller (but usually the standard
range is to 49.9C).
Is this thing sitting all apart? Are the sensor leads grounded at any
point? (Unplug the temperature controller, remove the sensor from the
bath and measure the leads to earth with an ohmmeter - power off).
It is possible they have grounded one of the sensor leads to reduce
bobble in the controller- the E5CS is/was an early switchmode supply
controller. Usually Pt100 probes are floating wrt to the shell.. is
the shell floating on the new probes? Any vigorous EMI sources kicking
around? Is the developer tank earthed?
Does it make a difference if the controller is calling for heat or
not?
One possiblity is that there is not much wrong, but the setup is not
properly wired so the controllers appear to be malfunctioning. Maybe a
heater is leaking AC current into the tank. If you take an AC
voltmeter and hold one lead in your hand and touch the other in the
tank do you read any voltage?
If you replace, be sure to use a decent auto-tune PID controller-
AFAIR, the C41 process is pretty fussy .. IIRC (frm a long time ago)
the spec is +/-0.1F, which is not easy.
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
anorton
Apr 15, 2013, 7:27:21 PM4/15/13
to
"Cydrome Leader" <pres...@MUNGEpanix.com> wrote in message
chemicals like developer.
Cydrome Leader
Apr 15, 2013, 8:20:05 PM4/15/13
to
> room temperature, but okay..
>
> There are other types of RTDs.. but the old "US Standard" alpha =
> 0.00392 is not very much different from the DIN standard at 40C (less
> than 1 degree C). The old J Pt100 Japanese standard was similar to the
> obsolete US standard. Everyone uses the Euro standard now, pretty
> much.
>
> What you are saying does not make a lot of sense. What is the
> temperature of the developer? 100F is 37.8C, so very close to what you
> say is the upper limit of the controller (but usually the standard
> range is to 49.9C).
The installed omron controllers max out at 39.9C, which really doesn't
>
> There are other types of RTDs.. but the old "US Standard" alpha =
> 0.00392 is not very much different from the DIN standard at 40C (less
> than 1 degree C). The old J Pt100 Japanese standard was similar to the
> obsolete US standard. Everyone uses the Euro standard now, pretty
> much.
>
> What you are saying does not make a lot of sense. What is the
> temperature of the developer? 100F is 37.8C, so very close to what you
> say is the upper limit of the controller (but usually the standard
> range is to 49.9C).
give much wiggle room. The operating procedure for the machine is ignore
what the controllers say, but trim the reset pot on the front panel and
fiddle with the numbers until the the temp measured in the tank with a
normal thermometer is correct.
> Is this thing sitting all apart? Are the sensor leads grounded at any
> point? (Unplug the temperature controller, remove the sensor from the
> bath and measure the leads to earth with an ohmmeter - power off).
> It is possible they have grounded one of the sensor leads to reduce
> bobble in the controller- the E5CS is/was an early switchmode supply
> controller. Usually Pt100 probes are floating wrt to the shell.. is
> the shell floating on the new probes? Any vigorous EMI sources kicking
> around? Is the developer tank earthed?
to late 1980s. It's not clear if the Omron controllers are for the
international Pt100 or Japanese version. They are all fairly old so it's
not out of the question they're all bad.
I've not tested if the new probes are floating or attached to the red or
white lead. Flipping polarity doesn't seem to have any effect. I've not
examined how and if the tank is directly grounded. There is a chain driven
mechanism that raises and lowers rack of film into the tanks. The machine
is mostly single phase 208. Motors and pumps are run with contactors and
heaters and fans with "advanced" solid state relays.
The highest tech thing in those machines are the omron controllers.
There's no know EMI sources, just other similar machines.
> Does it make a difference if the controller is calling for heat or
> not?
forward- replace/rebuild the bad part and they work again.
> One possiblity is that there is not much wrong, but the setup is not
> properly wired so the controllers appear to be malfunctioning. Maybe a
> heater is leaking AC current into the tank. If you take an AC
> voltmeter and hold one lead in your hand and touch the other in the
> tank do you read any voltage?
wrapped around the probe's metal sheath dunked into the developer tank
doesn't cause weird readings of air temp, hand temp or even temp of a
container of developer. Just thought about it now, but the test of is this
an electrolytic reaction problem is bridge the container of developer with
probe to the main tank with a wire. Maybe the wire itself isn't reactive.
The cable running from the operator panel to the back of the machine is
three conductor, white, brown and green with a braided shield. I believe
the shield is chassis grounded, but I'd have to look at it again. The last
working but not OEM probe was somehow lost while trying to source
replacements, so it's not clear how or what was even connected internally.
> If you replace, be sure to use a decent auto-tune PID controller-
> AFAIR, the C41 process is pretty fussy .. IIRC (frm a long time ago)
> the spec is +/-0.1F, which is not easy.
constant pumping somehow make it possible.
Pete C.
Apr 15, 2013, 10:34:04 PM4/15/13
to
elements, is it possible that the original probes were insulated could
relate to their housing acting as an electrode in a chemical battery
with the developer solution? Your test with a dunked wire might not have
had enough surface area or been the correct metal to reproduce the
effect?
Cydrome Leader
Apr 15, 2013, 11:25:48 PM4/15/13
to
read high temps, but we'll see.
Joe Gwinn
Apr 16, 2013, 9:29:13 AM4/16/13
to
In article <kkigbs$8ha$1...@reader1.panix.com>, Cydrome Leader
I'd check simple things first. Like a thermal open circuit in the new
RTD sensor. I've had that problem. Use an ordinary ohmmeter to read
the RTD resistance as it warms up in a bowl of hot water from the tap.
Joe Gwinn
RTD sensor. I've had that problem. Use an ordinary ohmmeter to read
the RTD resistance as it warms up in a bowl of hot water from the tap.
Joe Gwinn
Pete Keillor
Apr 16, 2013, 10:23:06 AM4/16/13
to
4-wire preferred, and that's pushing it, but I seem to recall the
Omrons taking 3. I always specified 4-wire and put two leads from one
end under the + terminal, the other two under the measurement and -
terminals. I also always used ungrounded sheathed elements. Don't
recall ever seeing a grounded RTD, but you could get t/c's that way.
A/C heater leakage played havoc with grounded t/c's.
Pete Keillor
Spehro Pefhany
Apr 16, 2013, 12:49:35 PM4/16/13
to
On Tue, 16 Apr 2013 09:23:06 -0500, Pete Keillor
<Pete.K...@gmail.com> wrote:
>
>If the spec is +/- 0.1F, then a 2-wire RTD ain't going to get it.
>4-wire preferred, and that's pushing it, but I seem to recall the
>Omrons taking 3. I always specified 4-wire and put two leads from one
>end under the + terminal, the other two under the measurement and -
>terminals. I also always used ungrounded sheathed elements. Don't
>recall ever seeing a grounded RTD, but you could get t/c's that way.
>A/C heater leakage played havoc with grounded t/c's.
>
>Pete Keillor
He's got a 3-wire cable going to two-wire very near the end. Probably
<Pete.K...@gmail.com> wrote:
>
>If the spec is +/- 0.1F, then a 2-wire RTD ain't going to get it.
>4-wire preferred, and that's pushing it, but I seem to recall the
>Omrons taking 3. I always specified 4-wire and put two leads from one
>end under the + terminal, the other two under the measurement and -
>terminals. I also always used ungrounded sheathed elements. Don't
>recall ever seeing a grounded RTD, but you could get t/c's that way.
>A/C heater leakage played havoc with grounded t/c's.
>
>Pete Keillor
okay provided the end is reasonably well controlled.
Perhaps worth stating that 3-wire RTD compensation requires that the
three wires (well, usually it's only two of the three, but you may not
know which ones) be as close to identical as possible, since one wire
is used to compensate for the resistance of another.
Four wire is theoretically independent of that kind of matching
requirement, but nobody outside of laboratories uses it much.
Stanley Schaefer
Apr 17, 2013, 12:17:43 PM4/17/13
to
it wouldn't work). You no doubt have an electrochemical reaction
going on between contents, sensor and some fastener or plumbing
somewhere in the tank. If I were speccing sensors for such an item,
they would be glass-encased if immersed. It wouldn't have to be much
of reaction to get a few millivolts out on the leads, enough to mess
up any temperature signal. It wouldn't take a lot to seal the end of
a suitable glass tube, drop the temp sensor in that and see if the
problem goes away when dunked in the tank. It would take a pretty
sensitive VOM to measure the voltage at that level, they DO exist, but
usually aren't a shelf item at Lowe's. We generally used a mirror
galvanometer and a Wheatstone bridge when messing with such things in
the lab.
Stan
Joe Gwinn
Apr 18, 2013, 9:47:39 AM4/18/13
to
In article
<db32fe5a-c846-4e0d...@u20g2000yqj.googlegroups.com>,
The sensor appears to be a 100-ohm RTD, not a thermocouple, so
millivolts should not have that big an effect. And the RTD is probably
encased in but galvanically isolated from a stainless-steel probe.
I'm betting on a bad RTD.
Joe Gwinn
<db32fe5a-c846-4e0d...@u20g2000yqj.googlegroups.com>,
millivolts should not have that big an effect. And the RTD is probably
encased in but galvanically isolated from a stainless-steel probe.
I'm betting on a bad RTD.
Joe Gwinn
Stanley Schaefer
Apr 18, 2013, 12:31:58 PM4/18/13
to
On Apr 18, 7:47 am, Joe Gwinn <joegw...@comcast.net> wrote:
> In article
> <db32fe5a-c846-4e0d-b75d-c2a0ed172...@u20g2000yqj.googlegroups.com>,
> Joe Gwinn- Hide quoted text -
>
> - Show quoted text -
Have you checked that the housing IS isolated? I've been surprised
more than one time that way.
Stan
> In article
> <db32fe5a-c846-4e0d-b75d-c2a0ed172...@u20g2000yqj.googlegroups.com>,
>
> - Show quoted text -
Have you checked that the housing IS isolated? I've been surprised
more than one time that way.
Stan
Cydrome Leader
Apr 18, 2013, 1:25:06 PM4/18/13
to
Stanley Schaefer <sta...@prolynx.com> wrote:
>> > it wouldn't work). ?You no doubt have an electrochemical reaction
>> > they would be glass-encased if immersed. ?It wouldn't have to be much
controllers to play with. Panasonic still hasn't contacted me back, so
they lose, which is too bad, I liked the timers and stuff back when it was
Aromat.
As for the probes, I took one for testing. I can't get it to read wrong
from 50 to 120F. It jives with my analog TelTru thermometer, which is
actually more accurate than the thermocouple that came with the last Fluke
meter. The fluke has more digits, but they're all wrong.
With a standard meter, there's no connection between the stainless sheath
and the leads. I don't know what the internal construction is, so I'm not
going to try any 500 volt hipot-like tests, and I doubt it's rated to that
anyways.
milivolts should not have an effect on a RTD, but how electrically
isolated the current temp controllers are is unknown, and again, I can't
do a 500 volt hipot test on them, and I can't locate data on what the
isolation ratings are to start with.
So the plan is down to
- try the probe I tested
- try a probe inside something glass. There's never glass tubing around
when I actually need it for some reason.
- try a new controller from the sales guy
>> > going on between contents, sensor and some fastener or plumbing
>> > somewhere in the tank. ?If I were speccing sensors for such an item,
>> > they would be glass-encased if immersed. ?It wouldn't have to be much
>> > of reaction to get a few millivolts out on the leads, enough to mess
>> > up any temperature signal. ?It wouldn't take a lot to seal the end of
>> > a suitable glass tube, drop the temp sensor in that and see if the
>> > problem goes away when dunked in the tank. ?It would take a pretty
>> > sensitive VOM to measure the voltage at that level, they DO exist, but
>> > usually aren't a shelf item at Lowe's. ?We generally used a mirror
>> > galvanometer and a Wheatstone bridge when messing with such things in
>> > the lab.
>>
>> The sensor appears to be a 100-ohm RTD, not a thermocouple, so
>> millivolts should not have that big an effect. ?And the RTD is probably
>> > the lab.
>>
>> The sensor appears to be a 100-ohm RTD, not a thermocouple, so
>> encased in but galvanically isolated from a stainless-steel probe.
>>
>> I'm betting on a bad RTD.
>>
>> Joe Gwinn- Hide quoted text -
>>
>> - Show quoted text -
>
> Have you checked that the housing IS isolated? I've been surprised
> more than one time that way.
I'll be back tomorrow and an Omron rep is dropping by with some
>>
>> I'm betting on a bad RTD.
>>
>> Joe Gwinn- Hide quoted text -
>>
>> - Show quoted text -
>
> Have you checked that the housing IS isolated? I've been surprised
> more than one time that way.
controllers to play with. Panasonic still hasn't contacted me back, so
they lose, which is too bad, I liked the timers and stuff back when it was
Aromat.
As for the probes, I took one for testing. I can't get it to read wrong
from 50 to 120F. It jives with my analog TelTru thermometer, which is
actually more accurate than the thermocouple that came with the last Fluke
meter. The fluke has more digits, but they're all wrong.
With a standard meter, there's no connection between the stainless sheath
and the leads. I don't know what the internal construction is, so I'm not
going to try any 500 volt hipot-like tests, and I doubt it's rated to that
anyways.
milivolts should not have an effect on a RTD, but how electrically
isolated the current temp controllers are is unknown, and again, I can't
do a 500 volt hipot test on them, and I can't locate data on what the
isolation ratings are to start with.
So the plan is down to
- try the probe I tested
- try a probe inside something glass. There's never glass tubing around
when I actually need it for some reason.
- try a new controller from the sales guy
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