Temperature Differences Between Thermometers

A common issue with temperature/humidity measurement is apparent discrepancies between two thermometers. You can assemble any number of thermometers and more than likely they will all read a little differently (as will hygrometers). There are a number of reasons for this:

  1. Each thermometer has its own accuracy.  Two thermometers with accuracies of +/- 0.5C can differ from each other by up to 1.0C subject to additional issues below.
  2. Each thermometer is calibrated to a specific temperature, meaning they become less accurate as they move away from their calibrated temperature.
  3. Also temperature and humidity are inter-related and a thermometer will read a little differently at a constant temperature as humidity changes. Each thermometer will respond differently to various temperature/humidity combinations.
  4. Lastly, electronic thermometers use linear approximations which can also introduce differences.