A capacitance sensor for the water content of desiccant wheels

A capacitance sensor was designed to measure the water content in desiccant wheels. 24 AWG (American wire gauge) single conductor wires were constructed to be the probe. Prototype sensors of two probe lengths inserted into the wheel and two numbers of wires were prepared. Four locations of the desiccant wheel were tested to verify if the measured trend is consistent with the weight variation and the physics sense. After series of tests on two desiccant wheels from different suppliers over the regeneration process, the variation of capacitance values is agreed with that of water content by weight measurement. It is believed that the capacitance is able to be a good indicator of water content, and the current design is economical and suitable to be a continuous online sensor. It will be very helpful to determine the end of dehumidification or regeneration process.