Trouble in PID Paradise

[CedarSmoker]

Here's the deal. I heat the smoker to a 150⁰. I am confident that this is the actual temperature as confirmed by 3 probes placed near the thermocouple. The PID reports the temperature as 130⁰ so in calibration setting I enter +20. The PID now reports 150⁰. Life is good right? Not so much because I next increase the target temperature to 220⁰ and let the PID do it's things until it reaches a PID temperature of 220⁰, however all the probes indicate that the actual temperature is near 300⁰. I am eager and motivated to correct the thermocouple issue. Your thoughts?

 

[Florida Chris]

What smoker? How's the probe placement? Luckily for you one of the best PID tuning tutorials I've seen was just posted on here by A AmIaPilotYet .

Step by Step Guide to Calibrate PID Settings

Recently, I’ve installed an Auber AW-1520H PID controller to my SmokinTex PRO 1400 model smoker. This model of smoker comes with a manual thermostat base temperature controller which makes it a great candidate to upgrade with a PID controller. Due to the simplicity of the smoker’s system, it...

www.smokingmeatforums.com

 

[CedarSmoker]

What smoker? How's the probe placement? Luckily for you one of the best PID tuning tutorials I've seen was just posted on here by A AmIaPilotYet .

https://www.smokingmeatforums.com/threads/step-by-step-guide-to-calibrate-pid-settings.328645/[/URL

It's a diy smoker. Here's a descri...te probes, each mounted near the TC. [/QUOTE]

 

[CedarSmoker]

What smoker? How's the probe placement? Luckily for you one of the best PID tuning tutorials I've seen was just posted on here by A AmIaPilotYet .

Step by Step Guide to Calibrate PID Settings

Recently, I’ve installed an Auber AW-1520H PID controller to my SmokinTex PRO 1400 model smoker. This model of smoker comes with a manual thermostat base temperature controller which makes it a great candidate to upgrade with a PID controller. Due to the simplicity of the smoker’s system, it...

www.smokingmeatforums.com

I studied the step-by-step guide. The PID settings on my inkbird seem to work correctly. I say this because if I set the target temperature to 225⁰ the PID will hold it there within a degree or two. The problem is that the actual temperature reported by 3 independent probes placed close to the TC report actual temperature 100 or more degrees higher. While the PID "thinks" it's holding steady at 225 I'm actually turning meat into charcoal.

Cheers,
Joe

 

[normanaj]

JC in GB has experience with Inkbird PIDs.

 

[normanaj]

Those settings are specific for the Auber.

 

[dsk]

Generic PIDs generally support multiple types of sensing elements. Errors occur if the sensor type does not match the sensor type setting of the PID. For example, the PID might be set to expect a type J thermocouple, when in actuality a type K thermocouple is in use. I've also experienced absolutely crap PIDs with major errors I've bought off Aliexpress, though I would not expect this from Inkbird.

 

[JckDanls 07]

Errors occur if the sensor type does not match the sensor type setting

This is the first thing I thought of as well ...

 

[CedarSmoker]

Generic PIDs generally support multiple types of sensing elements. Errors occur if the sensor type does not match the sensor type setting of the PID. For example, the PID might be set to expect a type J thermocouple, when in actuality a type K thermocouple is in use. I've also experienced absolutely crap PIDs with major errors I've bought off Aliexpress, though I would not expect this from Inkbird.

The sensor type setting is set to K and the thermocouple is a k-type supplied by Inkbird.

 

[JC in GB]

Here's the deal. I heat the smoker to a 150⁰. I am confident that this is the actual temperature as confirmed by 3 probes placed near the thermocouple. The PID reports the temperature as 130⁰ so in calibration setting I enter +20. The PID now reports 150⁰. Life is good right? Not so much because I next increase the target temperature to 220⁰ and let the PID do it's things until it reaches a PID temperature of 220⁰, however all the probes indicate that the actual temperature is near 300⁰. I am eager and motivated to correct the thermocouple issue. Your thoughts?

Are you connecting the thermocouple wires directly to the PID controller? If you are running it on some kind of connector tabs or added wire to increase the length, dissimilar metals in the control loop will cause error to be introduced in the thermocouple feedback signal. Also, make sure you have selected the right thermocouple type. Most PID smoker controllers run on a type-K thermocouple. You may also just have a bad thermocouple. Try a new one. Type-K thermocouples are really inexpensive. My $0.02.

JC

JC

 

[dsk]

A picture of your probe mounting would be most helpful. If you have it screwed through the wall of your smoker it may be conducting heat outside the chamber, and the junction may indeed be significantly lower than the cooking air temperature. I have fought with this issue in the past.

 

[dsk]

As JC suggests, placing a different K thermocouple inside the chamber with your other probes may help isolate the issue.

 

[CedarSmoker]

Are you connecting the thermocouple wires directly to the PID controller? If you are running it on some kind of connector tabs or added wire to increase the length, dissimilar metals in the control loop will cause error to be introduced in the thermocouple feedback signal. Also, make sure you have selected the right thermocouple type. Most PID smoker controllers run on a type-K thermocouple. You may also just have a bad thermocouple. Try a new one. Type-K thermocouples are really inexpensive. My $0.02.

JC

JC

I can check the boxes on a couple of the items you mentioned. I've confirmed that the thermocouple is indeed a k type and that my PID is set to read a k type thermocouple. Also, the thermocouple is wired directly to the PID. Which vendors do you recommend or I can purchase a replacement k-type thermocouple?

 

[CedarSmoker]

A picture of your probe mounting would be most helpful. If you have it screwed through the wall of your smoker it may be conducting heat outside the chamber, and the junction may indeed be significantly lower than the cooking air temperature. I have fought with this issue in the past.

I'll try to post a picture of my probe mounting tomorrow. I do have it screwed through a recessed hole in the 1/2 inch cedar wood wall of my smoker. It makes sense that it may be conducting heat outside the chamber because I have been waiting to make sure everything works alright before I insulate and put the 2nd layer of cedar on the back. I'm not sure how far back from the tip of the thermocouple the junction is but if it's a 1/2 inch or more that it's almost certain to be causing this behavior. Thanks for the great and helpful reply.

 

[CedarSmoker]

Generic PIDs generally support multiple types of sensing elements. Errors occur if the sensor type does not match the sensor type setting of the PID. For example, the PID might be set to expect a type J thermocouple, when in actuality a type K thermocouple is in use. I've also experienced absolutely crap PIDs with major errors I've bought off Aliexpress, though I would not expect this from Inkbird.

I bought a "kit' off Amazon that had the Inkbird PID, SSR, heat sink, and thermocouple so everything there matched up well. The PID was factory set to a k-type type TC. I really think that all of the equipment is okay and all signs point to the newb diy'er as the problem here. Another post mentioned the TC mounting can be the problem and proper mounting and insulation might fix the issue. I'll report back tomorrow after I apply those fixes.

Thank you for your reply,
Joe

 

[CedarSmoker]

A picture of your probe mounting would be most helpful. If you have it screwed through the wall of your smoker it may be conducting heat outside the chamber, and the junction may indeed be significantly lower than the cooking air temperature. I have fought with this issue in the past.

Ayd requested:

 

[Up_In_Smoke]

A picture of your probe mounting would be most helpful. If you have it screwed through the wall of your smoker it may be conducting heat outside the chamber, and the junction may indeed be significantly lower than the cooking air temperature. I have fought with this issue in the past.

Based on your picture, I think what dsk mentions could easily be the source of your problem.

Try taking your control TC out of the mounting device and move it well into your smoker.
Put your other 3 probes around your control TC and hold them in place with bread wraps or cable ties.

Put your temperature compensation value back to "0" (I think you said you had raised it to +25 or so??)
Gently bring your smoker temp up to 150 or so and note your readings. Then increase by 10 degrees, rinse and repeat.

 

[CedarSmoker]

Based on your picture, I think what dsk mentions could easily be the source of your problem.

Try taking your control TC out of the mounting device and move it well into your smoker.
Put your other 3 probes around your control TC and hold them in place with bread wraps or cable ties.

Put your temperature compensation value back to "0" (I think you said you had raised it to +25 or so??)
Gently bring your smoker temp up to 150 or so and note your readings. Then increase by 10 degrees, rinse and repeat.

I'll give that a try and report back.
Thank you for the follow up.
Joe

 

[dsk]

Those button probes are not good in this application. I replaced exactly one of those for exactly this reason. I have a one inch long probe now that is better.

 

[Muleystalker]

You also want to put something inside the smoker to replicate a big piece of meat that will take time to heat up, say 3-4 bread pans full of sand. These electric smokers with PID's do funny things with temps when run empty. It would be a good idea to finish with the inside of the smoker, ie insulation and such, before messing with the settings on the PID. I also think the previous poster hit the nail on the head with that Button thermocouple, I have not seen one manufacture use those in their electric smoker, its always at least 1-2" long.