problem with AD620 - measuring AC current

[mandecom]

problem with AD620

Hi,

I am using AD620.
inputs are connected accross a resistor through which AC current of 50 Hz is flowing.

i am getting 75mV across that resistor which i want to amplify and clamp to +ve side.

what should be the connections of ground and ref?

 

[FvM]

problem with AD620

The main point is to keep the common mode specification for the differential input (also for ref, but that's mostly not critical).

In practice, you may want to connect the AD620 ground to AC ground, respectively one of shunt terminals.

 

[mandecom]

problem with AD620

i tried that. i connected ground of AD620 to one of the terminals of shunt but its not working. i am getting constant output 2.5Vrms irrespective of input.

 

[FvM]

problem with AD620

Other points can be wrong, e.g. power supply range. You should show the complete circuit to make the problem understandable.

 

[dick_freebird]

problem with AD620

How do you ensure that the resistor (input) terminals remain
between the instrumentation amplifier supplies, in your circuit?

You might make a "virtual input reference" by a resistor
divider from the two input terminals, high enough impedance
that it does not corrupt the measurement but low enough
that it can drag the (presumably isolated) amplifier rails to track
any reasonable common-mode impulse.