How Humidity Sensor Devices Work

Posted by , on Jun, 2015

There are many different places a humidity sensor is used. The most common is in HVAC (heating ventilation and air conditioning) systems to turn on and off humidifiers and dehumidifiers.

Additionally, a humidity sensor may be used all on its own simply to measure the humidity in a room or specific area. This information is important in some manufacturing process as well as food prep areas, wine cellars and applications in vehicles. They are also used in hygrometers to gather information at weather stations and to help with weather forecasting.

In specific storage areas, such as in archives, libraries, and even in laboratories where humidity control is essential to inhibit the growth of mold, mildew or bacteria these sensors are a very important part of the environmental control system.

The Measurements

To measure the humidity, the sensor is determining what is known as relative humidity. To determine relative humidity, the humidity sensor has to measure both the air temperature as well as the moisture in the air. The temperature measurement is critical as warm air can hold more moisture than cold air, and this is essential in providing a correct reading of the relative humidity.

How They Work

The typical humidity sensor is very simple in design and construction. Most home and commercial HVAC systems use capacitive sensors. These include two electronic conductors that are separated by a non-conductive polymer film. The two conductors create an electron field to trap moisture in the air on the film. The more moisture collects on the film the more the voltage changes between the two conductors.
The humidity sensor can detect this voltage change and convert it into a calibrated measurement. While not as accurate as some of the more complex and specialized hygrometers used for measuring the environment and in scientific research, these are very effective for general home and commercial use.

Specific Options

In a variety of different specialized applications resistive humidity sensor or thermal conductivity, humidity sensors may also be used. These are less sensitive options than the capacitive sensors and, in the case of a thermal conductivity sensor, measure only absolute humidity and not relative humidity.

All humidity sensor designs are built to withstand exposure to moist air, but all will need to be replaced eventually as dirt and contaminants come into contact with the sensor components.

At Gopher Electronics Company, we offer a top selection of OEM humidity sensor models. To see our complete inventory go to

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Posted by , on Jun, 2015

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