offset voltage in Isolation amplifier

[TeChSaVvY]

I use isolation amplifier (ISO124).
Input signal is +/-10 V analog voltage.
I get considerable offset voltage in the output.
That offset voltage increases with increase in input voltage.
Since its a isolation amplifier, how to nullify offset voltage???

 

[Spehro Pefhany]

I use isolation amplifier (ISO124).
Input signal is +/-10 V analog voltage.
I get considerable offset voltage in the output.
That offset voltage increases with increase in input voltage.

Then it's not offset voltage, it's a gain error (perhaps with an
offset voltage added to it). Unless I misunderstand what you are
saying here.

Since its a isolation amplifier, how to nullify offset voltage???

That part has REALLY crummy DC specs. As much as +/-50mV Vos with
2mV/V change vs the supply, and 200uV/K drift. The gain error is
pretty small. Given that, you can null it at the input or the output
with about equally bad results.


Best regards,
Spehro Pefhany

 

[TeChSaVvY]

With applied 0V input 20 mV is at output. As soon as I increase input
voltage, that 20 mv
offset inreases accordingly. I dont want that 20 mv(offset?) at output.

 

[Spehro Pefhany]

With applied 0V input 20 mV is at output. As soon as I increase input
voltage, that 20 mv
offset inreases accordingly. I dont want that 20 mv(offset?) at output.

Just tack an op-amp at the input or output and add a small adjustable
(eg. trimpot) +/- offset voltage to the input or output. See any
introductory book on op-amps. The details depend on what power
supplies you have available and other things. I'd be inclined to work
with the output, all other things being equal, if the input voltage
will always be in the 10V range.


Best regards,
Spehro Pefhany