Thermocouple problem?

[waksupi]

My pot has been giving me problems the past couple days. It had been working fine. Now, I set the temperature on the PID, and it will go over 50 degrees hotter. And at that, the lead in the pot is only at oatmeal stage. Do I have a bad thermocouple? I've been fighting nozzle freeze, too.

[Mike W1]

From Auber's Q&A

To check the controller.

a. The first thing to do is to verify the controller is OK. This can be done very easily.
Just use a copper wire to short the terminals for the TC input (e.g connect terminal 4
and 5 for 2342 or 2352; connect terminal 6 and 7 for 1512, and connect terminal 9
and 10 for 2363). The reading of the controller should be about the ambient temperature,
where the controller is located.

If that is the case, the controller is fine. To be 100% sure the controller is fine; check
the parameter setting for the input type. Make sure it is set to K type.

If reading does not show ambient temperature, change all the parameter to the initial
setting listed in the instruction manual. If it still not shows ambient temperature, the
controller is defective.

If “a” passes, go to next step.

b. The next thing to do is to verify the system (the controller and the sensor) is OK.
You need to remove the TC from your installation, connect it directly to the controller
(without extension and connectors). Dip the TC in ice/water mixture (70%: 30%). The
sensor body need to be complete immersed. Read the temperature in 5-10 minutes.
The reading should be close to 0 °C or 32 °F. You can also do this in boiling water.
The reading should be close to 100 °C or 212 °F at sea level. Important, you can not
calibrate the system in the air because some of the sensors may take 30 minutes to
response in the air.

If the system fails to pass “b”, then the TC may be defective.

If the system passed test “a” and “b” then, the problem is the set up.

Disconnect any load from the output of the PID.
Turn unit on, should display "EEEEE" followed by
it's boot up sequence. If the probe is out in the
open air, the display should begin reading the
ambient room temperature. Let the unit sit and
check every so often to see if it turns off. It should
stay on 24/7. If you happen to see it turn off, flip
the switch and turn it back on. If it does not come
up and run through the check right away, it could
be a heat problem with the PID. Also make sure
that your wiring connections are all good.
If the PID unit stays on with no load, try it again
with the pot. If you have an amp clamp, you can
get an idea of the current that the pot is pulling
from the unit. We can work from there, but first
make sure the PID unit stays on with no load.

Temperature sensors -- there are RTD's or
thermocouples. If yours is a K type thermocouple, and
"The brand the OP has says EEEE = 'out of range' ", then
you probably have a loose or intermittent connection
on either the PID on the thermocouple terminals
or somewhere up to the thermocouple junction
itself. Else you could have a thermocouple that is
not rated for 700F. I would recommend you look
at the connections associated with the
thermocouple. Hope this helps.
Also a dirty connection on the power feed to the
PID could make the PID crash due to repeated
voltage collapses when the load is connected.

[waksupi]

I don't think that is applicable to my PID. I got mine from Timbo, and I have never seen a EEEEE reading on it at all.

[Mike W1]

I don't think that is applicable to my PID. I got mine from Timbo, and I have never seen a EEEEE reading on it at all.

Neither have I. Did you do either the ice or boiling water test? Easiest way to my mind to eliminate the TC as a suspect would be to substitute a different one and see if it solves problem or not. I notice that a lot of guys have spares as the ebay ones apparently do have some problems at times and I've got one as a spare. So far neither of my Auber TC's have been a problem though.

[waksupi]

Neither have I. Did you do either the ice or boiling water test? Easiest way to my mind to eliminate the TC as a suspect would be to substitute a different one and see if it solves problem or not. I notice that a lot of guys have spares as the ebay ones apparently do have some problems at times and I've got one as a spare. So far neither of my Auber TC's have been a problem though.

I'm going to test it when I get the time. I think that is my problem, though.

[popper]

Overshoot of pid is normal part of 'learning' programming of the pid. Insulation in many probes is not hi temp and will fail intermittently. When mine failed, wiggling the wire would change reading.

[bangerjim]

As cheap as those t/c's are most on here use, one should order a spare or two! They will fail due to the high temp. They are not industrial grade construction. The K junction at the tip may be rated to read the high temp, but the construction of the couple itself will fail.

bangerjim

[dragon813gt]

If you don't have any spare thermocouples go and buy around five anyway. I had one fail about two years into using it. They are cheap. If you have a spare it's easy to test them against each other as well.

[stag15]

If you want a good thermocouple, get an industrial one. 1/4" diameter type K. You can find them from WIKA instruments.