loop powered level transmitter

[hemnath]

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.

 

[KlausST]

Hi,

What capacitance and what microcontroller.

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

Klaus

 

[hemnath]

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.