Hi there,

I am trying to create a circuit to measure humidity in the air.
When I try to interpret the values obtained, they do not correspond to the table of values that the manufacturer of the HR202L provides.
Could someone explain to me the possible errors in my circuit or my calculations?

I am using this HR202L sensor that varies its resistance based on the humidity in the air.
I want to increase the sensitivity of the measurement, so I decide to use an opamp as differential amplifier configuration.
The reference voltage is the midpoint between the voltage when humidity is maximum and the voltage when humidity is minimum.


Thank you all and please let me know if something is very incorrect or poorly explained.

 

Hi naspilla,
Are you assuming that the Humidity plot is linear?
E

Added:
Check out the link.

https://forum.allaboutcircuits.com/threads/humidity-sensor.87040/

 

It would be difficult to calibrate and verify your measurements unless you have know humidity references.
The first step would be to select various fixed resistances at selected %RH test points to verify your system.

Note that the R vs %RH is nonlinear and is also a function of ambient temperature.

 

please let me know if something is very incorrect

According to the datasheet the sensor needs a 1.5V (max) 500Hz-2kHz AC supply, not (nearly) 7.5V DC as in your simulation.