loop powered level transmitter

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hemnath

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Hi,
I'm designing a loop powered level transmitter which provides 0% for 4mA and 100% for 20mA.

I have some idea about how to use the XTR116.

But how to measure the capacitance and fed to micro-controller.

Please help.
 

Hi,

What capacitance and what microcontroller.

Please provide complete information, schematics, currents, voltages, measurement range and so an.

Klaus
 

For 470pf capacitance, instrument should provide 4mA.
For 1470pf capacitance, instrument should provide 20mA

Microcontroller: PIC18LF2520

Since it is a loop powered, the instrument should operate below 4mA. As I'm going to use PIC18LF2520 with the operating voltage of 3.3V, So the current consumption will be 1.7mA max. I have to use remaining 2.3mA for the capacitance measuring circuit. But what IC should i use to measure the frequency?

Please help.
 

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