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Measuring Frequency,waveform and inrush current of 240v

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NiHaoMike:
For voltage, use a power transformer with a rated primary voltage higher than the circuit voltage, like a 240V transformer for a 120V line or a 480V transformer for a 240V line. Or maybe use a step up transformer backwards. It should easily stay within the linear range.

For current, a Hall effect sensor is your best bet. Closed-loop nulling type for best accuracy and bandwidth, but that's a little overkill for mains use. Or a Rogowski coil, but those need compensation to be accurate with nonlinear loads.

Neilm:
The trouble I have found with current probes is the dynamic response. They work well when there is a steady AC signal, but the transient from the inrush current can overload them and you don't see all the data. I had a problem like that at work where the inrush in the design was more than the mains switch could take resulting in a loud "crack" if you turned it on at the wrong part of the waveform. Eventually I had to use a small resistor and an isolated scope to do the measurement. (Tektronics 2024 with proper isolation). Checking it against the Tektronics current probe showed me that the probe was not showing the full magnitude of the pulse - it was not even going into overload when it should have.

Yours

Neil

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