5.1.1. Thermocouples and thermoneedles
Thermocouples are standard sensors for the measurement of ambient temperature. Their small (i.e. thin) size and flexibility allows installation of many sensors in a honey bee colony (Stabentheiner et al., 2010). Due to their usually small sensor tip – and thus heat capacity – their reaction to temperature changes is fast. Sensitivity and reaction speed can be maximized by using small wire diameters (ones close to 12 µm are available; for example see Omega Engineering Inc., http://www.omega.com). Accuracy depends primarily on the electronic thermometer in use, including the accuracy of the reference (cold) junction compensation in the connector (junction) block. During outdoor measurements in sunshine, the electronic thermometer may not be exposed to solar radiation. Thermal gradients in the connector (junction) block may lead to high measurement errors (up to several °C). Similar errors may occur if ambient temperature changes rapidly, for example when stepping outside. Equilibration of the device is always recommended for utmost accuracy.