Current Sensing


My project is to measure current and compensate the offset current in the test bench.. So i choose an instrumentation amplifier INA 333 according to the requirement connected across the Shunt resistor... I measured the Voltage when i removed the load... which is the error current flowing through the shunt resistor... Now How should I compensate the error ...find the attachment below...can I use difference amplifier for Vref and the output of I can get the error out..and can I feed back this error to the buffer amplifier feedback to make the error zero...thanks

Offset can be done in software.

I think you will be facing other problems.

Why the +/- 12volt and +/-5volt on your notes. The INA333 has a max operating voltage of 5.5volt total.

If you supply the INA from e.g. +2,5volt and -2.5volt, you have no problems with the input.
But you loose half of the A/D resolution.
Unless you use 1.1volt Aref in your code, and set REF to half of Aref.

If you supply the INA from a single 5volt supply, You have full A/D resolution, but you can't ground the current sense resistor.
Because minimum input voltage is V- +0.1volt (add current sense voltage).

Don't forget to add a resistor between INA and Arduino to limit current if the opamp swings below ground.