What is the purpose of the oxygen sensors built-in heater?
In order to keep condensation from forming on the sensors Teflon membrane (where oxygen diffusion occurs), the built-in heater is designed to warm the sensor to a temperature slightly above the ambient temperature. This is particularly important in soil applications where the relative humidity is normally at 100%. For this reason, it is recommended that the heater be continuously powered. Once condensation forms on the membrane, the sensor must be removed from the humid environment and allowed to dry before the condensation evaporates and the signal returns. If the heaters are turned off and condensation forms, the heaters don’t supply enough energy to evaporate the condensation once they are turned back on. The heater requires a 12 VDC input and consumes about 74 mW of power. This works out to about 6 mA of current draw.
