Thermocouple/PID calibration

falls · Post by **falls** » Sat May 24, 2014 3:56 am

Just wondering if anyone has calibrated their PID controllers to ensure they are reading the right temperature.
I just hooked up my 2 PID's and connected the same TC to each and one read 16-17C and the other 20-21C. I tend to agree with the 16-17C given what ambient temp seemed to be (didn't feel like 20C).
My PIDs have a compensation setting. They recommend creating a water bath with 70% ice and 30% water which should equal 0C (32F). Then put the TC in the water bath and see what the PID reads. If it isn't 0C then you use the compensation setting to make it read correctly.

Alternately any ideas in wiring of why they would read differently.
Both are wired to identical TC ports then have TC wire between the quick connect port and the PID. Have hooked up the +/- correctly. The connection wires perhaps are different lengths, but then again the actual TC wires could be different lengths and you wouldn't want that to affect accuracy.

MadRussian · Post by **MadRussian** » Sat May 24, 2014 4:27 am

to make sure TC is not the problem I would suggest connect the same TC to both PIDs, one at the time, to see if you get same or different reading. If reading the same TC problem if different PID problem[/b]

falls · Post by **falls** » Sat May 24, 2014 5:48 am

It was the same TC plugged into one and then plugged into the other with 4-5 degree C difference

gozaimaas · Post by **gozaimaas** » Sat May 24, 2014 5:59 am

Yes I encountered this issue with my sestos pid units. I set mine up at room temp and at 100°c in a boiling jug of water.
Once I got them perfect the values were quite different in both units but I cant remember how much.

falls · Post by **falls** » Sat May 24, 2014 6:37 am

Compensation values were different?

gozaimaas · Post by **gozaimaas** » Sat May 24, 2014 3:27 pm

Yeah.
Im in malaysia atm on my way home from japan. When I get back I will look into it and post the compensation values I ended up with.
I spent days messing around with the bloody things

falls · Post by **falls** » Sat May 24, 2014 6:25 pm

I used my first one straight out of the box. Luckily it looks like it reads accurately without calibration.

gozaimaas · Post by **gozaimaas** » Sat May 24, 2014 7:24 pm

You getting 100°c in boiling water and returning to an accurate ambient temp?

falls · Post by **falls** » Sun May 25, 2014 3:47 am

I did a 70% ice and 30% water ice bath. Allowed it to sit for 10 minutes to equilibrate.
My original PID read 1C and the new one 5C.
So I compensated down by 1C and 5C so they both read 0C in ice water bath.

Then did boiling water and both read 97C
Water boils at 100C but is affected by altitude. At my altitude of 150m it is meant to boil at 99.5C.

Accuracy of a K type thermocouple is meant to be +/- 2.2C.

I guess where I have it set now is reading a little low, but at the end of the day it is the equality between top and bottom that is most important so when you set 80C in both blankets they both are at the same heat (even if it is 82C rather than 80C).

I guess the boiling water test is probably more accurate than the ice water bath. Probably should take 1C off the compensation on each PID so it reads 98C in boiling water at my altitude.

Made a start on some new skis this weekend. Also was looking at one of my templates that was a little bowed from not storing it flat. Lets just say trying to flex an MDF template back a bit flatter like hand flexing a ski doesn't end well. Damn.

gozaimaas · Post by **gozaimaas** » Sun May 25, 2014 8:16 am

Yeah you should be good to go now ;-)

falls · Post by **falls** » Mon May 26, 2014 3:02 am

If you really want to get technical I should have been boiling distilled water rather than tap water

gozaimaas · Post by **gozaimaas** » Mon May 26, 2014 4:28 am

Haha yeah, or you could just build some skis!

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Thermocouple/PID calibration

Thermocouple/PID calibration