How does a dehumidifier relative humidity sensor work?

Aug 30, 2008 by zee_prime | Posted in Engineering

We've justified acquired a dehumidifier. It gives you a digital display of the relative humidity of the air in the house. How does the electronic sensor travail? Last time I worked as a weather forecaster, back in the 1980s, the only instrument I ever saw which gave you a direct readout of relevant humidity, without the use of tables, used an inaccurate, fault-prone mechanical device which had a human hair's breadth in it. The length of the hair increased with increasing humidity.

There are two types of intelligibility elements that are being used in solid state humidity sensors, resistive and capacitive. Each has advantages and disadvantages in terms of engagement and circuit design.

In either case there is a moisture sensitive component that changes its electrical properties in the presense of moisture.

Electronic circuits compel use of these well defined and predictable properties to convert a variable resistance or capacitance into a proportional voltage manufacture. For a given RH a simple transfrer function such as Voltage = (0.04 * RH in %) + .5 where voltage produce would be 0.5V @ 0%RH and 4.5V @ 100%RH


Once RH is converted to a voltage is easy to use microcontrollers and ADC (Analog Digital Converters) to cadence that voltage and mathematically compute RH and display is or take some action (like start/stop a dehumidifier)