Temp Control Visited yet again I'm sure

[Catch-22]

Question,

I recently got a Johnson Analog Control and wanted to see how accurate the dial is to real temp. It has been in the fridge for five days now and the dial is set at 34. I have two digital thermometers as well sampling the same area as the controller probe. Therm 1 is at 41 and Therm 2 is at 40. Is there a way to calibrate the Johnson to get it more in line with the two thermometers?

 

[chemman14]

that may be fairly accurate. I believe the analog control has a 3 degree swing for the temps

 

[Catch-22]

Yeah it does both +/- to help protect the compressor. My question is really whether I can make a calibration adjustment to get me more into the ball park regarding correct temp. Rather than just peeling off the dial rotating it to 40 and gluing it back on.

 

[Catt22]

No. You can't calibrate the Johnson analog controller and there's really no need to. Monitor the actual temp just as you are doing with a digital thermometer. Adjust the controller as needed and don't worry about what the analog dial is set to. The dial resolution is only a very crude 2 deg F anyway. Remember that the controller has a built in differential. IIRC, it's 3 deg F which means that when the controller switches on it will stay on until the temp drops to 3 deg below the set point, then switch off. The refrigerator design and the location of the temp probes can make a difference and may explain the discrepancy between the thermometers and the controller setting. Being that you have two thermometers monitoring the temp and they are in fairly close agreement, I would let them govern. Six or seven degrees difference between the controller and the thermometers is more than I would expect it to be, but what it is is what it is I guess. Mine usually differ by only a couple of degrees. I would also expect that the actual temp read by the thermometers would be lower than the controller setting. I don't have an explanation for that.

 

[Catch-22]

Thanks yeah I thought it strange they were so different. I actually taped all three probes together to ensure I was sampling the same area. I appreciate your answer. Cheers

 

[Cliff897]

It'll likely be a sight more accurate than your fridge.
Most fridges lie lie lie.