<P> The reading produced by a conductor carrying a very low current can be increased by winding the conductor around the clamp several times; the meter reading divided by the number of turns is the current, with some loss of accuracy due to inductive effects . </P> <P> Clamp meters are used by electricians, sometimes with the clamp incorporated into a general purpose multimeter . </P> <P> It is simple to measure very high currents (hundreds of amperes) with the appropriate current transformer . Accurate measurement of low currents (a few milliamperes) with a current transformer clamp is more difficult . The range of any given meter can be extended by passing the conductor through the jaw multiple times . For example a 0--200 A meter can be turned into a 0--20 A meter by winding the conductor 10 times around the jaw's core . </P> <P> Less - expensive clamp meters use a rectifier circuit which actually reads mean current, but is calibrated to display the RMS current corresponding to the measured mean, giving a correct RMS reading only if the current is a sine wave . For other waveforms readings will be incorrect; when these simpler meters are used with non-sinusoidal loads such as the ballasts used with fluorescent lamps or high - intensity discharge lamps or most modern computer and electronic equipment, readings can be quite inaccurate . Meters which respond to true RMS rather than mean current are described as "true RMS". </P>

Clamp on dc ammeter work how does it work