kewakl (Customer) asked a question.
We have some chambers that are controlled with P1/Solo SLM1/SLM2
We notice that when the controls enclosure temperature rises, our indicated temperature drops.
I did some experimenting with SLM1 and SL4824-RR.
*I must state here that I have not totally duplicated the parameters between both controllers*
I have a 24VDC lamp with an attached J-type thermocouple. The Solos are controlling lamp temperature. I have an EA9-T8CL communicating with the Solo. I connect each Solo separately.
If I gently heat the thermocouple connector with a heat gun, I see differing responses.
The temperature indicated by SL4824 falls, then steps back toward the original temperature.
The temperature indicated by SLM1 falls. Just falls. It looked like it began to rise again, I have not continued heating the connector as I do not wish to destroy it.
I did not find CJC in the SLM1 documentation, but I am certain that the SLM has some compensation.
I did not find CJC in the SL4824 documentation, but I see the tab at terminal 5.
The Solo BASIC documentation DOES indicate CJC in the Specification table in the Input Accuracy section. I do not have a Solo BASIC to test.
Thermocouples have polarity and this could be why the SLM reading is falling. Have you tried reversing the thermocouple leads on the SLM unit and testing again?
These controllers are on my desk.
I have the same type thermocouple wire on both controllers.
They track (within thermocouple placement error) each other until I heat the terminals on the controllers.
I have updated my test scheme.
I saved the parameters from the SLM to a config file and then loaded that file in to the SL4824-RR and re-ran my test.
Videos and images will be attached to this thread.
I have both controllers connected to Solo Configuration Software. I allow the controllers to return to ambient (with fan-forced air) and for the PV readings to be close.
Then I heat the terminals with a heatgun until it is a bit uncomfortable for me to have my hand in the airflow.
I have captured images of the solo software tabs for each controller and a video of both faceplate values diverging away from PV.
The 4824 graph
The SLM1 graph
Faceplate - diverging responses
Diverging temperature responses
Could this be due to response times of the temperature rise and compensation of the CJC? The response time to a change in ambient temperature depends on a lot of things: how the CJC is accomplished, the time for the CJC temperature to rise and fall, the response time of the CJC, the rate the metal connector temperatures rise and fall, etc.
This testing is to resolve the problem of the different response times while your control cabinet temperature rises. Your testing proves that the two differently-designed controllers do respond differently to changes in ambient temperature. And your application cannot tolerate this different response between the two controllers. If this is all true, I don't know you could "fix" this other than have the same-designed controllers, or maintain control cabinet temperature.
A heat gun is a good testing tool, but could bring the temperature above the allowed temperature for some components, depending on air flow, heat gun temperature, etc.
(I like your testing, at one point, I was a test engineer)
We will not be using different families of temperature controllers in the same controls enclosure.
I am trying to characterize what we are seeing. I am not looking at this as a fault or problem with the components.
I do expect that my heating of the terminals is much too quick for CJC response.
We are leaning toward some type of cabinet cooling - and/or moving the major heat-generating components out of the cabinet.
Thank you for your input.
Thanks for the explanation. Yes, interesting phenomenon. As far as your plan: "cabinet cooling - and/or moving the major heat-generating components out of the cabinet", good plan, we have used both the "heat exchanger" coolers, and "thermo-electric" coolers with great success, and no outside air! (ordered from from Automation Direct and EIC).
eicsolutions.com
(more care needed to stay within temperature specs for heat exchangers)
In some applications, where we know the ambient temperature will remain cool, and the only major heat-generating component is the transformer, we have used an external transformer like Automation Direct C1FC50LE.