what is clamp on ammeter

I am going to use a clamp on ammeter in my next practical. can anyone please tell me something about it?

Do you mean an AC current clamp-on probe? Not sure what other clamp you might be referring to.

AC Current probes clamp around a wire and measure the current going through it. It's basically just a coil inside that makes a small little transformer with the wire itself.

Can be A.C. or D.C. clamp-on ampmeter. D.C. must use Hall-effect sensor which have become common in new meters.

It measures current by measuring magnetic field generated by current flow in a wire.