Capacitive sensor - calculation???

[north2012]

Hi,

I would like to calculate capacitance of planar PCB capacitor (Please see attachment). Substrate is FR-4 and I would like to print no interdigital structure because I think that it will be easier to calculate with this simple structure.

View attachment C.pdf

Which equation I can use?

How I can calculate capacitance of interdigital capacitor?



Thanks.

 

[D.A.(Tony)Stewart]

The combination of surface acoustic waves in the IDF and electromagnetic waves gets rather complex. Good Luck.:???:

https://www.rle.mit.edu/cehv/documents/81-Proc.IEEE.pdf

 

[erikl]

How I can calculate capacitance of interdigital capacitor?

Try this paper!

 

[D.A.(Tony)Stewart]

Have you considered a differential bridge arrangement (Dry/wet) ? THis may null out the sensor capacitance but not the temperature sensitive conductance. Handheld meters with dual range 0-20mS and 0-2mS are temp compensated. https://www.grainger.com/product/OAKTON-ECTestr-11-Dual-Range-Conductivity-8EJR7?s_pp=false

(milli-siemens =mS)