How can this sensor module work ?

Other Hardware Sensors
1

I have purchased this hygrometer module,

and I found this schematic

http://www.uctronics.com/hr202-humidity-resistance-sensor-module-lm393-chip-for-arduino-mcu-p-1545.html

When I connected it and measured the A0 value with a multimeter I was first surpriced to find it be 5.1 V (=Vcc).
Also with the multimeter the resistance was measured to be 19.8 kOhm (at 22.5 C). According to the table in this documention

ftp://imall.iteadstudio.com/Sensor/IM120712018/DS_IM120712018.pdf

the relative humidity would roughly be about 65%. But the multimeter (can measure relative humidity) it's only 35% and this figure agree with the weather forecast.
I think the measured voltage is due to the capacitor being charged to 5.1 V. So how can this module possible work?
It does not seem to work as voltage divider which would be the case without the capacitor C2. And even if I only consider the HR202 resistance the figure is not correct. How could I possible get a correct measurement of relative humidity from this product?

2

If that schematic is correct? You shoud have AC (pin1) show a voltage near 3?
The capacitor does not alter this.

3

knut_ny:
If that schematic is correct? You shoud have AC (pin1) show a voltage near 3?
The capacitor does not alter this.

Why should it not be correct? How can you arrive to near 3 Volt? I measure 5.1 V (=Vcc).

4

Schematic shows 10k series sensor (also 10k in a specific environment). Point AC is connected to this voltage divider.
If the comparator isnt blown, its input impedance is very high -> shouldn't affect voltage.
..nor will the capacitor affect voltage.
Connect AC to an analog input - read it with analogRead - print result.
If u get 1023, the circuit isnt as described or a component is malfuntioning.