# Augmenting a capacitance base humidity sensing circuit

Given an electronic device that measures humidity using a capacitance based humidity sensor, how would one alter the circuit to make the humidity reading lower?

From what I can see without taking the device out of service, there is a surface mounted capacitor wired as follows:

simulate this circuit – Schematic created using CircuitLab

Figuring it was worth a try, I removed C1 and it seemed to make no difference in what the device reported as the relative humidity. Unfortunately, I can not find a schematic for the device.

Here is an article describing humidity sensors, but I am unable to design a circuit alteration based on what I'm finding there.

• After posting this question, I learned that the sensor is on a chip that delivers a digital signal (diy.stackexchange.com/a/129341/4323). This, of course, means there's no simple circuit to cause the RH reading to decrease, as I had hoped.
– Dale
Dec 19 '17 at 21:20

To make it read lower you could add a capacitor in series. The total capacitance is, of course, $C_S = \frac {C_1 C_2}{C_1 + C_2}$.