Hi Prahlad,

Your plan to go in for a Rogowski coil appears OK considering the huge current of 25000 Amp that you plan to measure, as the transfer function only contains the di/dt term.

As to local availability of Chopper stabilized op-amps I remember to have used a TLC2654 for some temperature application front end circuit. I am sure you will be able to find equivalents from Intersil range - which is another popular brand that is available locally.

Sounds a challenging application. While on this you must have given thought to the following also ?

- When you said "Offset also will also be integrated .." were you referring to the op-amp offset or that produced by your input circuitry ? With a chopper stab op-amp you need only worry about the later ?

- What happens to the EMF, when the di/dt term becomes zero or near zero like when the welding current is constant - at least theoritically ?

- Scaling down a parameter of 25000 to a few Volts, your overall noise margin of the whole system can get very tricky ?

- How about calibration?

Good luck .

Raghu