Measuring line current

Lots of folk have been curious about current transformers and the like
to measure the moderate currents in the TC primary. After a few minutes
research in the Newark Electronics catalog, here you go:

F.W.Bell has AC and DC current sensors, which generally provide some
sort of voltage or current output proportional to the measured current.
Of particular interest should be the hall effect sensors, which have a
60kHz bandwidth, cost <$30, and provide a DC voltage proportional to the
instantaneous current, in ranges up to 600 Amps. This will actually give
you decent waveform information!

Similar parts are availble from Honeywell, except they are cheaper. For
instance, the CSLA series, about $20, provides a voltage proportional to
the current.

Finally, traditional current transformers are available: about $26 in
ratios like 50:5, 100:5, 150:5, and 200:5.... mfr by Crompton.