How Resistive Type Humidity Sensor Works? Learn with Diagram

The Resistive Type Humidity Sensor works by changing its resistivity with the changing of humidity. It is constructed with a very low resistive material such as Solid Polyelectrolytes, Deposited polymer, salt, or treated substrates. Also, the two electrodes are placed in such a way that maximum contact between them can be achieved.

It is a passive sensor as it can not generate the electrical signal itself. It just changes its resistance so an external power supply can be used to generate the electrical signal.

Here, you can see the diagram that shows the internal construction and working concept of the resistive type humidity sensor.

You can see there are two electrodes arranged in such a way that they have maximum contact area. Now when the humidity is constant there are no changes in the output resistance but when the humidity changes the resistance also be changed. In general, there is a very low resistance between the output terminals as it is constructed with low-resistive materials. And the electrodes are made with gold, silver, or platinum.

The resistivity changes with inversely proportional to the humidity. That means when the humidity increases the resistivity will be decreased and when the humidity decreases, the resistivity will be decreased. So by measuring the output resistance, we can measure the humidity. Also, it can be used in a current or voltage drop measuring where it can be connected in series. And by measuring voltage or current, the humidity can be measured indirectly.

The main advantages of the resistive humidity sensor are low cost, simple construction, small, size, it can be placed at a far distance from the circuit, and it is easy to install.

The main disadvantage of resistive humidity sensors is their sensitivity affected due to chemical vapor or other contaminants.

Read Also: How Capacitive Humidity Sensor Works? Learn with Diagram

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