how to measure AC current

[FvM]

Increase C4 or the sensor series resistance.

 

[aliyesami]

Increase C4 or the sensor series resistance.

ok I will increase R2.
the circuit will still function the same and measure all the range of input conductivity right?

 

[FvM]

The series resistance makes the relation between conductance G and frequency slightly non-linear. You can calibrate the circuit by connecting different fixed resistors.

 

[aliyesami]

Hi Fvm
Will changing the value of series resistor jeopardize the quality of input signal ?

 

[Warpspeed]

Increasing the resistor will lower frequency and effect linearity.
Changing the capacitor just lowers the frequency.

 

[aliyesami]

Oh ok then i will change the capacitor. Shohld i increase it?

 

[Warpspeed]

Frequency will decrease in direct proportion to capacitor increase.
100nF = 12Khz max (what you have now)
120nF = 10 Khz max
150nF = 8Khz max