How Capacitive Humidity Sensor Works? Learn with Diagram

There are various types of humidity sensors available in the market. In this article, we are going to learn how the capacitive humidity sensor works. It is also known as a capacitive RH sensor. It is a very economical and basic humidity sensor. A capacitive-type humidity sensor can measure humidity from 5% to 90%. It is a passive type of sensor which means it can not generate an electrical signal itself. Generally, it changes its output capacitance while the humidity changes.

Here, you can see the diagram which shows the internal construction and its working concept. This diagram will help you to understand very quickly the whole concept.

You can see, it is basically a capacitor whose dielectric constant changes when the humidity changes. It has two electrodes and in between them, the hygroscopic polymer film material is used as the dielectric medium.

There are three figures in the above diagram. The first one shows the basic internal construction. The second one shows when the humidity is constant and the third one shows when humidity changes.

When there are no changes in the humidity the dielectric property also be unchanged or remain constant. But when the humidity changes, the dielectric property will change, hence the output capacitance will be changed. Now measuring the output capacitance we can measure the humidity.

So, you may understand, the working principle of the capacitive humidity sensor and its internal construction is very simple. In practice, the whole arrangement is placed on a silicon substrate and the electrodes and the dielectric material is coated by a protective polymer layer.

The main advantage of the capacitive type humidity sensor is, we can measure the humidity of a particular object with the help of a special design and arrangement. We take that object as a dielectric material.

Read Also: How Thermal Type Humidity Sensor Works? Learn with Diagram

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