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designing a capacitance tester

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grant

New Member
greetings

I want to build a moisture content tester based on measuring the capacitance in the sample. The moisture will act as dielectric of the capacitor. In short, I am looking for suggestions, ideas and simple cicuit diagrams of measuring capacitance.
 

stevez

Active Member
I have some experience with this - with paper as the "dielectric" of interest. The resulting capacitance was the 'C' in an RC circuit - it became clear that resulting RC constant was varying with the moisture content of the paper and the thickness of the paper. From that experience I'd offer that you understand the impact of thickness as well as moisture on your particular measurement process.
 

Roff

Well-Known Member
The dielectric constant of water varies dramatically with temperature, and the conductivity varies dramatically with purity. Unless you have temperature compensation and your moisture is deionized and cannot be contaminated, or you plan to measure complex impedance in order to separate capacitance from resistance, I think you are in for considerable difficulty. In fact, even if you do those things, I think you are in for considerable difficulty. Even if you are measuring a thickness change, I think these factors will come into play. Sounds like a fun challenge, though. :)
 
hi

Please reply me related circuit diagram to measure the capacitor with compensation of temperature for find out moisture contain.
 
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