i try to use the code below, but it only show a biggest value
Can anyone help me to calculate it into RH value,thx 
Humidity_Sensor.ino (2.08 KB)
Which humidity sensor is it ? You can copy a link in your post.
SN-HMD_MOD humidity sensor
OMG I Just found this documentation for that module. SN-HMD-MOD Getting Started Guide - Google Docs
In there I find
This is example code for humidity sensor module. Please download the complete code at the product page.
Then on the linked page under "Q&A" I find
Question:
I have this type of HR202 humidity sensor and I have no idea how to convert the analog result to HR%. I haven't found any exemple code at internet. I already look through the attachment given,but it dint help.can i have the formula of this sensor to read the humidity reading?
Answer:
Hi, as highlighted in the description, this sensor will only show humidity changes, it will not provide absolute humidity reading. If you need absolute humidity reading, please check HIH6130 breakout board.
Looks like you've been taken for a mug if you've bought it 
Useless sensor.. see last part of datasheet http://www.microelectronicos.com/datasheets/HR202.pdf
This is the one you need. (software available)
knut_ny:
Useless sensor.. see last part of datasheet http://www.microelectronicos.com/datasheets/HR202.pdf
There's a useful looking table in that, until you notice "Impedance performance ( at 25°C VAC 1kHz)
So to measure humidity, you should measure it's impedance at 1 khz ac AND compensate for temperature. Might just as well use a bit of string for what it's worth.