7.3. Generating a thermal gradient

The thermal gradient is usually characterized by the temperature and location of the temperature pessimum (usually at the coolest spot) and one or more global (36 °C) or local temperature optima (32-34 °C). While the coolest temperature in the arena depends on ambient temperature, the global and local optima are generated by heat lamps. A special computer program polls the temperature sensors in a given time interval and determines their temperature. Based on these measurements, a heat map is calculated for the entire arena (Fig. 15) which can be logged and used as a feedback for the maintenance of a stable thermal gradient. Depending on the desired temperature and the actual temperature of deliberately designated control sensors, the control software turns the heat lamps on or off individually to achieve a simple yet effective (ΔT = 0.1 °C) automatic control over the thermal gradient.