convert capacitance signal to voltage signal

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sumani

Joined Mar 12, 2009
8
hi..
I'm an engineering faculty undergraduate, and new to this field. i m using HCH-1000 Capacitive Humidity Sensors for my project. now I'm facing a problem to connect it with PIC.
i would like to know that how to interface this sensor with PIC micro controller. could you please suggest me a circuit diagram that can be used to connect humidity sensor HCH-1000-001 with the PIC 16f877a.

or simply could you please suggest a circuit to convert capacitance signal to voltage signal
capacitance varies in a range from 300 to 370 pF
the required out put voltage is 2V-5V


thank you
R.SuManAroObAn
 

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thingmaker3

Joined May 16, 2005
5,073
You could use the sensor as part of an oscillator and feed o/p to a frequency-to-voltage converter.

Or you could charge the sensor with a constant current source for a precise time interval and then sample voltage.

Or you could use the sensor as part of a capacitive voltage divider with AC applied, and run the o/p through an RMS converter.

Or you can do this: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=/netahtml/PTO/srchnum.htm&r=1&f=G&l=50&s1=6331780.PN.&OS=PN/6331780&RS=PN/6331780
 
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