Most cafés calibrate probes in boiling water (100 °C). That’s wrong for day-to-day use.

The correct method is the ice-water test at 0 °C because that’s the critical range you actually care about (0–8 °C for fridges, 0–5 °C for chillers).

Process: fill a glass with crushed ice and a splash of water, stir, wait one minute, insert probe, adjust ± until it reads 0.0–0.2 °C.

Do this monthly and log it. EHOs now routinely test your probe against theirs. If yours is out by more than 1 °C you lose points instantly — even if all your recorded temperatures were “correct”.

Thirty seconds a month saves the entire inspection.