GoKawiilJames Bricknell/CNET
The most important part of any thermometer testing is accuracy. We use a medical-grade thermometer as our baseline for accuracy and test the meat probe variance to that temperature.
Ice water testing
Testing the accuracy of a thermometer usually involves a cup, some ice cubes and water. Due to the nature of water it can be a liquid and a solid at 32 degrees Fahrenheit (0C) so we can reliably get it to be that temperature. By filling a tall glass with ice cubes and adding water — chilled water so the ice doesn't melt — you can bring that water down to 32 degrees F.
We then insert both the medical-grade probe and the meat probe we are testing and stir it until the medical grade thermometer reads 32 degrees F. When that happens we record the temperature reading of the meat probe we are testing to see what, if any, variance there is.
Why don't we use heat?
You would think that using heat would make more sense. After all, these are probes for grilling meat, so high heat is more important, right? Unfortunately, heat is dependent on many factors, such as altitude and pressure, that we can't always control. The freezing point of water is always the same, though, wherever you are, so we can ensure accuracy independent of location.