View Full Version : Temp Discrepency/calibration question

05/01/2007, 08:36 PM
Hello all... wondering if you can provide some advice.

I've recently purchased and installed an ACjr. After getting it installed in the display part of my Nanocube 24, I've noticed that its reading is far different that the other temp probes I have. I know that the instructions read that the temp probe is calibrated out of the box, but the discrepencies I'm reading concern me, espeically when I get ready to begin programming ( I just have live rock right now).

Here are the readings

Coralife digi temp probe 1 - 79.9
Coralife digi temp probe 2 - 79.9
Arctica chiller temp reading - 79.3
mecury thermometer in tank 80.0

Aqua controller JR - 81.1

Hmmm... any advice here? Do I assume that the ACjr is correct and forget the rest or do I calibrate the ACjr to the other reference. Or, is this simply an acceptable variance? Thanks so much for any help you can provide... this is my first tank and trying to get it all set up right before the livestock goes in.


05/02/2007, 10:47 AM
Have you tested one of your other probes in ice water to check that they are close to correct?

05/02/2007, 11:03 AM
Ice water is not a good way to calibrate the probes. The tank temperature is too far away from the calibration temperature.
To know with 100% which temperature is correct you must compare the temperature readings w/ a NIST traceable.
The AquaController's temperature probe was calibrated to a NIST traceable source, and will be within +- 0.5F out of the box (assuming you didn't change the calibration offset). Most thermoments have accuracy no greater than +-2 or +-3. Your readings are well within that tolerance.


05/02/2007, 11:41 AM
Curt, that is very interesting. I didn’t realize that temperature probes would need to be calibrated that close to the running temperature to be close to accurate.

What calibration method do you recommend when a NIST reference is not available? I for one have lost my initial calibration settings.

05/02/2007, 11:53 AM
I don't know any other way, but to compare a known accurate thermometer to the one you are trying to calibrate.


05/02/2007, 03:00 PM
Thanks Curt. If what I''m hearing is correct, then I should use the probe from the ACjr (i have not messed with the calibration) as the benchmark... and let that do the dictating for my controls.

Is that a fair assessment of your advice??? Not wanting to put words in your mouth, of course;)

This will be important to know because I will be setting my chiller up and will have to "do the math" and factor in the discrepancy between the chiller temp and the ACjr temp so they work in concert. Make sense?

Again, thanks for your help and counsel...it is a great product.


05/03/2007, 04:29 PM
Yes, I would say the Jr. temperature probe reading is very accurate.