Current sensing using OP-Amp shunt resistance

[adnan012]

Hi

I am looking for a DC current sense circuit which can measure 10-30A current with 0.5A accuracy. The shunt is 1mR. Which configuration of op-amp is suitable for this application? I want to use LM358.

Best regards

 

[FvM]

Datasheet doesn't explain in detail. Looking at figures 20 and 26 clarifies that input stage is supplied from IN+/- pins if Vin exceeds Vs.

https://www.ti.com/lit/gpn/ina181

 

[dick_freebird]

It may be that there is more than is shown. Datasheet
and app note figures are simplified and obscured for
reasons.

Perhaps there is a front end resistor divider to bring
pin common mode range into amp common mode
range, made up for by the second stage gain being
higher than you think it is. Some art to balancing the
guts of instrumentation amplifiers to maximize signal
range in some aspect or other, and trades.