Which temp probe to trust?

[KJAhp098]

Yesterday afternoon, my Apex temp alarm started to go off saying the temp was above 84°. I looked at the graph, and the temp shot up out of nowhere. This is the 2nd time it's done this in the past month or so.

Then, I looked at one of my inkbirds, which I use only for monitoring, and it said the temp was 77°.

Then I looked at my Hygger temp monitor and it said 72°.

Then I plugged in my 2nd inkbird temp monitor and it says 76.3°.

Then I plugged in my 2nd Apex temp probe and I get 83.2°

How can 5 different temp probes give me 4 completely different numbers? Which one do I trust?

 

[doubleshot00]

Go to petsmart/walmart/petco and get a stick on thermometer. At least you can glance at it and be like meh that's not right. The apex has to be calibrated so imo its probably wrong. The inkbirds are probably correct.

 

[blaxsun]

I assume they were all placed in the same area? I'd clean all the probes first (I let mine soak in EzeClean for a few hours, then scrub off) and then see if the results change after.

You could also get one of those cheap digital temperature readers that stick to the inside of the tank (I think I used a Fluval) to give you an idea of which ones are closest.

I switched from an Inkbird to Helio heater system and haven't looked back (both it and the two Apex temperature probes are within 0.25 degrees of one another).

 

[KJAhp098]

Yes, all probes are in the same area before the heaters.

I'll pick up a stick on thermometer.

Also, the temp on my Apex doesn't change after calibrating the temp probe. Not sure if that has anything to do with it.