Calibrating Temp Probes


New member
Did you read the fine print? It has an accuracy of + or - 1.5 degrees. That is the same as the difference between the two readings you are now getting. So if the tank was 79 this could record anywhere from 77.5 to 80.5. We sometimes just have to accept that the quality of equipment we use for testing, because of the price we are willing to pay in the market, just aren't very accurate. If everything is doing well just watch for spikes, either high or low


New member
I work in the kitchens. My cooks carry thermometers everywhere they go and probe everything they serve. The method they use to calibrate temp probes is with ice and water.

Fill a glass (or bigger depending on size of probe) with ice to the rim. Top it off with water and mix it around for a good minute (until you see lots of condensation on the glass). Stick the probe in and calibrate it to 0c.


New member
One-point calibration, as you suggest, really isn't calibration. Your cooks' thermometers will be great at testing temperatures near freezing, but probably not so good at measuring higher temperatures, like safe serving temperatures. It all depends on the probe/meter. I recall when this question has come up before, the Apex probe won't read accurately at all around freezing. So "calibrating" it there will do more harm than good.

It's really no different than calibrating a refractometer - if you're calibrating using a single point, you want that single point as close as possible to what you're trying to measure. In our case, you'd want to set the temp probe to something that you *know* is around 80 degrees. Pretty tough.

If you're determined to have an exact reading, you can buy a thermometer that is pre-calibrated to NIST standards. Expect to pay a bit for it. Then use that as your "actual" temperature and set the others based off that. For me, that *actual* temperature isn't as important as the consistency. If I'm off by a degree or two, it's not the end of the world. My fish and corals are used to 79 degrees... whatever that may actually be!


Premium Member
It is more important to avoid temperature fluctuations than worrying too much about what the actual temperature is. The ice water method can work, especially when you also do the same thing with boiling water, however many temp probes will not work well in that wide of a range. Buying a lab grade glass thermometer from a supply house that deals with scientific labs is your best bet. Inaccuracies with a thermometer like that would probably be extremely small.