RMS AF voltmeter

Since measuring alternating voltages and currents is not a straightforward matter, it is not to be wondered at that errors occur frequently. Non-sinusoidal measurands (quantities to be measured) in particular demand a fair knowledge and experience from the test engineer/technician. Most of the difficulties are caused by the fact that measuring instruments invariably only have a simple rectifier at their input. This is reasonably all right at very low frequencies, but even then, it does not take account of the shape of the measurand. Alternating voltages can be measured accurately only by a true-r.m.s. voltmeter, which unfortunately is a fairlyexpensive instrument. The instrument desribed in this article offers a viable and inexpensive alternative.