Hello Mr. Unmesh Oke,

Your problem sounds is simple to solve. Since you already have an analog meter measuring the 75 MilliVolts across the shunt and is working reliably, then all of the hard work has been done for you.

Tap across the meter movement and feed that into a simple differential operational amplifier set up with a gain to give you a 0-5 volt DC output. Take that signal feed it into a 8 bit Analog to Digital converter (ADC) and then you will have a digital value which you can manipulate in your controller system.

This is old hat for measuring AC current (0-500 AMP) and AC voltage (0-500 Volts) in the industrial electronics sector. I developed such a circuit years ago (see below diagram) which has worked reliably.

Good Luck.
Regards,
Charles Bannister
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