PWM solver
January 1st 2006

A free downloadable application note from www.fluke.co.uk (via the 'Applications' drop down menu) explains how a handheld Fluke 190 Series ScopeMeter makes it easy to troubleshoot pulse-widthmodulated (PWM) variable speed drives using the oscilloscope's unique measuring and triggering functions to analyse the voltagefrequency radio.

To verify that the voltage/frequency ratio is constant over the working range of a Variable Speed Drive (VSD), the Vpwm function available on some Fluke Series ScopeMeters gives a true measurement of the voltage actually applied to the motor while simultaneously measuring the frequency: the use of a true-rms voltmeter in these circumstances would give an erroneous reading of the full bandwidth signal. The Connect-and-View triggering of the ScopeMeter also ensures a stable display, whereas the complex modulated waveforms produced by VSDs often make it difficult to obtain a stable picture on other oscilloscopes.

With safety certification to 1,000V CATII and 600V CAT III, Fluke says its ScopeMeters help users to solve virtually all electronics measurement problems encountered in the field.

The ScopeMeter 190 Series of handheld, two-channel oscilloscopes include 196 and 199 models, with either monochrome or colour screens.

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