Thermocouple Calibration (Little Chief Mod) (SOLVED)

  • Some of the links on this forum allow SMF, at no cost to you, to earn a small commission when you click through and make a purchase. Let me know if you have any questions about this.
SMF is reader-supported. When you buy through links on our site, we may earn an affiliate commission.

JohnnyGunn

Newbie
Original poster
Aug 9, 2022
3
3
Hey everyone! First time poster from Alberta!

Not sure if this is the proper place to post.

I recently took my Little Chief smoker out of retirement and decided to do a few modifications (just for fun) to see if I can smoke something other than perch in the thing...so I added a 1500W hot plate.

But since I'm a tinkerer (and a home brewer with an electric brewery in the basement), I had some odds and ends left over, I figured I'd use them and installed a PID (XMT-7100, ripoff of the Auber SYL-1512A) to control the temps a little better. Everything seems to be running smoothly...minus one major component...the temperature calibration of my K-type thermocouple! I calibrated in ice water...hit perfectly. Then I went to the boiling water calibration...I had to adjust the Psb setting by about 5F on the PID, no big deal. But now I've had the probe in the closed smoker (no heat, just doing an "air" test) with a known accurate probe (NTC BBQ thermometer) and I'm getting very different readings after 30 minutes:
- known good probe 124F
- K thermocouple wired to the PID 109F

It gets worse if I start heating with wood chips in the pan...I'll get a difference of 60F between the good probe and the PID reading, 20 or so minutes into the "test"! Before I auto-tune, I need to make sure my temps are accurate.

What can be going wrong? Would a blower or extra vent holes help move the air around and stabilize things? Not totally sure, because I would think that 2 measuring instruments should get the same readings in the same environment, no? I'm used to calibrating these things in liquids...so I need help!

Cheers!
 
Last edited:
Problem solved!

I spoke with an engineer buddy of mine that was completely stumped by my issue...until I sent him a picture of the thermocouple. He thought that since it was one of those "stubby" threaded probe ends, the threads and retaining nut were acting like a heatsink and falsifying my readings.

I switched out the probe for a 4" Type-K and problem solved! I can say that it wasn't a malfunctioning thermocouple because I tried two of the same type of stubby ones and both had the same issue.

I've got my Little Chief up to 225F as we speak, confirmed by my trusty Javelin Pro!

Cheers!
 
SmokingMeatForums.com is reader supported and as an Amazon Associate, we may earn commissions from qualifying purchases.

Latest posts

Hot Threads

Clicky