PID Thermocouple Issue

jbolt

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I just powered up a PID for the first time on my heat treat furnace build. The thermocouple temp display on the PID changes erratically, large swings from tens to hundreds.

The PID is an Auberins SYL-2352P. Manual Here.

The thermocouple is a TC-K-KLN type K high temp thermocouple for kiln.

I have it wired it per the manual and double checked the settings, the polarity and connections. I also tried grounding the negative side to the enclosure per the manuals suggestions but it still jumps around erratically.

Anyone have an idea as to what is causing this?
 
My first thought is poor connections on the thermocouple wire, second is power supply problems.
 
I assume you are using Wiring diagram shown in 5.5 Figure 6 which has the k type thermocouple (TC) wired to terminal 4 of the controller which should be the (+) lead of the TC, and terminal 5 of the controller has the (-) lead of the TC. I have to assume it is running on the main power you selected as 120VAC or 220VAC and the controller appears to be operational at the selected voltage. You have only used thermocouple type wire (for k type TC) to connect between the TC and terminals 4, 5 of the controller and that you know you can't just use any old wire to do that. At 4.15 you have tried to set the digital filter by setting the range from 1 to 20 (have to start small and work up to 20 for filter). If the filter is set to 0 it is OFF and not used this is why you need to try using it by selecting 1. Since you are experiencing fluctuations in readings try 1 for a setting and work your way up to 20 to see where the filter begins to work. I would expect the higher the filter number the slower the response to temperature displayed rise or fall. Type K TC's react very quickly and in the application you have the controller should do a good job without worrying over filer response time, but it must be considered. At 4.7 you have set the controller to code zero so it knows it is a type K TC.

Now another place to look is at the TC and its wiring route, the voltage developed by the TC is very small and it remains very small even at temperature extremes in the range of the TC. Therefore you must route the TC and its wiring away from any electrical wiring carrying current. If you have the TC wiring run with A/C power lines, separate the TC wiring. When routing the TC wires, cross A/C wires at 90 degrees to minimize coupling.

Now how is it responding?
 
That model has an 'autotune' feature, and will explore for a while when you invoke it. It could be that you're
watching fluctuations because the little brain is experimenting with settings and hasn't learned the
furnace yet.
 
I assume you are using Wiring diagram shown in 5.5 Figure 6 which has the k type thermocouple (TC) wired to terminal 4 of the controller which should be the (+) lead of the TC, and terminal 5 of the controller has the (-) lead of the TC. I have to assume it is running on the main power you selected as 120VAC or 220VAC and the controller appears to be operational at the selected voltage. You have only used thermocouple type wire (for k type TC) to connect between the TC and terminals 4, 5 of the controller and that you know you can't just use any old wire to do that. At 4.15 you have tried to set the digital filter by setting the range from 1 to 20 (have to start small and work up to 20 for filter). If the filter is set to 0 it is OFF and not used this is why you need to try using it by selecting 1. Since you are experiencing fluctuations in readings try 1 for a setting and work your way up to 20 to see where the filter begins to work. I would expect the higher the filter number the slower the response to temperature displayed rise or fall. Type K TC's react very quickly and in the application you have the controller should do a good job without worrying over filer response time, but it must be considered. At 4.7 you have set the controller to code zero so it knows it is a type K TC.

Now another place to look is at the TC and its wiring route, the voltage developed by the TC is very small and it remains very small even at temperature extremes in the range of the TC. Therefore you must route the TC and its wiring away from any electrical wiring carrying current. If you have the TC wiring run with A/C power lines, separate the TC wiring. When routing the TC wires, cross A/C wires at 90 degrees to minimize coupling.

Now how is it responding?
Thanks Doodle! Filter was the ticket. Set to 1 the TC value settled to 30. I measured the temp of the inside of the oven with a infared thermometer at 80 so I added 50 to the offset. It is now holding between 79-80.

Next is figuring out a test program to verify the heating elements work. The manual is not very intuitive.

I eventually plan on doing a break in period to make sure the excess moisture is out but that will have to wait until I have more time.

Sent from my SM-G955U using Tapatalk
 
I don't see a ground terminal on that controller. Not heard of that manufacturer but that makes me suspect of them. You got the fix, but if you had troubling wiring issue, you could remove the entire controller, and TC and power up n the bench to verify. Use of Ice bath as well.
 
The fix didn't last. I came back to it later and when I turned on the PID the TC reading was +90 deg and fluctuating plus/minus 20. I removed the offset and have been trying different filter levels. Every time I go up a filter level the base TC reading would increase and still with fluctuations. When I got to filter level 7 the TC dropped to 90 and now is slowly falling, now at 71 +- 3 and slowly still falling. I don't really know what to make of it. I'll keep trying the filter levels. How long should it take the TC to stabilize?
 
When you get really tired on it. Remove the controller and wire it to a suicide plug for 120AC. You got some K type T/C wire.

T/C wires on side to controller and take the other side and just twist the wires together. crude, but it does work. No other wire types or terminal blocks etc. Red and Yellow wires right? Red ( -) Yellow (+)

Try a stable temperature to measure. Make one. Many options... get two big blocks of metal, sandwich the thermocouple in the middle and place them on the stove or hot plate at low setting. let it stabilize to equilibrium and thermal mass of metal will hold it there. Now you can mess with controller software. Perhaps it's software or unit is junk.

Look for a Default setting to clear out what you have done. Get unit back to how it was shipped from factory.

I'm thinking the warmer heat sink so you are up in the range of the K thermocouple. You could go with Ice water bath too.

What is upper limit for your heat treating processes? I have a K on one oven and a J on the other one.

If all that works out, let's talk about the rest of the wires and such in your oven control design.
 
ohh, T/C stabilize pretty fast. if you have isolated type a longer lag. that info can be found on specification sheet for those.
 
Good progress, I question the need for a temperature offset as the TC is giving the correct value for what it is exposed to. You may have to wait hours for the controller to auto tune. From what you describe I believe you now need to find a location in your oven where the temperature stabilizes. Having the TC too close to the heaters can cause wild swings. You can try location as well as shielding (example, a metal shield in front of the TC so it is not directly exposed to the heating source). I would have to go look at the manual again, can do later, but for now... The Solid State Relay (SSR) controls the current to your heater by turning the power ON and OFF, when power is ON to the heating elements either the controller will display a light or the SSR has a light (perhaps both do). What you should expect to see is a long ON time when you start heating. As the Present Value (PV), {PV is the temperature of the TC}, rises and gets closer to the Set Value (SV), the ON time of the SSR will decrease. So look at the SSR ON time light and from a cool or cold start its dwell time will change from a long blink to a rapid series of blinks. That is the indication that the controller is trying to get your Set Value (or Set Point) under stable control. At this time you do not need to run a calibration test of the TC and controller by using water baths or Infrared thermometer readings. The TC and Control are better to rely on right now since everything is new, connections are good, and you are experiencing some control.

The SSR must be properly heat sinked so it does not run hot in operation. Additionally SSR's always leak a little current so don't expect a complete OFF at the heating elements. The very small amount of current will not effect the heating. They don't wear out and give exceptional control of the load far superior to metal contacts.
 
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