# Design humidity sensor circuit board

#### cktan22

Nov 12, 2014
1
Hi everyone,

I am new to circuit board design. I am from mechanical background, so im not familiar with electronic stuffs. I am having a new project, to design a humidity sensor.

The humidity sensor that i have required
1. power supply = 1.5 VAC
2. operating frequency = 1 kHZ

So, now my question is, how to provide the sensor with 1.5 VAC and 1 kHz?

As i read through internet, it is possible to design an oscillator circuit to provide output of 1 kHz, but im not sure whether suitable for my application or not.

I attached the specification of sensor in this treat. Hope can get some opinion in working it out.

#### Attachments

• HR202 Humidity Sensor.pdf
110 KB · Views: 167

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,101
Welcome to our forum.

The datasheet states 1.5V AV max sine. This means any voltage lower than 1.5V is fine. You don't have to apply exactly 1.5V.
The datasheet also states frequency 500Hz - 2kHz. This means any frequency in this range is fine. You don't need to apply exactly 1kHz. 1kHz is used in the datasheet to evaluate a few performance parameters.
The only reason you have to use AC instead of DC is that the sensor uses organic material which will be destroyed by a DC current.

Here is application note that explains the operation of such a sensor and the required electronic circuit.
Note that the sensor used in this app-note has a characteristic similar but not exactly equal to the one you're using. But the circuit allows adjustment of offset and gain so it should work with your sensor, too.

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