Tuning temperature sensors?

[VanGoghComplex]

Since I built my new loop, my temp sensors seem to be reading a couple degrees C hotter than I believe. I put a little desktop thermometer in front of my case, directly across the intake grill from the fans, and it's reading 26.7°c, while the two sensors I have mounted directly behind the intake fans (on the fan hub supports) are measuring 28.6°c. So either the air is heating up 1.9° in the 29mm from the front of the fan to the back, or my 10k temperature sensors are off by a bit.

I've got four temp sensors wired into my system that I use to control things. Two are on the front intake of the case, which I average for detecting ambient temperature, and two are on the hottest and coolest parts of my loop, which I average for a coolant temperature. I then control my rad fans on the ambient/coolant delta temperature.

On a cold start, when I assume the coolant is going to be basically ambient, the coolant temp is also a couple of degrees higher than I would expect. I've got the tools to deal with this - Aquasuite lets you put an offset on any temp sensor, but I'm curious if it should be necessary. Do these 10k temp sensors tend to be so far off? A couple degrees C at room temp is a pretty big margin for error, but I'm not familiar enough with these sensors to gauge whether I should expect this inaccuracy.

 

[unholythree]

Couple of things: 10K NTC thermistors have a resistance that changes based on temp. The "10K" is the sensor's resistance in ohms at 77F.
Your Aquasuite thermometer/indicator/controller is really reading the resistance of the themistor and translating it to temp based on some resistance curve it's expecting. Higher resistance = lower temp.

Now that said there are actually a couple different types of 10K thermistors with slightly different curves but they all are 10K at 77F, and pretty close for the 10 or 20 degrees around 77.
An illustration by the HVAC controls manufacturer Belimo:

If you need to test a thermistor you check it against it's resistance table. For example: https://www.belimo.us/support/957181531 Maybe not the most detailed chart but you can find better googling.

TBH I'd probably trust the 10K thermistors over your desk thermometer, but the only way you'll really know is to have a calibrated thermometer to compare against.

 

[honegod]

boiling water = 100c/212f @ sea level = calibrate from there.