Multimeter hookup for Duty Cycle

Huw Powell audi at
Mon May 5 00:11:09 EDT 2003

> Duty cycle measurements give you the percentage of on time to off time of a
> voltage. For example, a 9 volt battery that is swiched on for 1 sec . .then
> off for 1sec . .then on . .then off . .etc . . .has a duty cycle of 50%.
> Can a voltmeter read this cycling voltage? Yes it can. Does the reading mean
> anything? Not usually. But, if you can calibrate your voltmeter against a
> known source . . . . you got yourself a duty cycle tool!
> You can calibrate your voltage meter against a known working unit in your
> car...
> This method will work for that one particular meter only, since this method
> involves the particular characteristics of a meter and its associated
> circuitry. Also, the duty cycle should be based on a fixed on/off frequency
> . . . .which on audi's I believe it is.
> I would welcome a discussion on this topic with some actual measurements
> taken with different voltage meters, analog as well as digital.

Whew... considering the number of variables that can affect this, not
least of which is that the graph is only useful for devices running the
same voltage, and it will very likely be a curve not a straight line...
the Sunpro meter has duty cycle on it, and runs what, about $60?

Still, pretty ingenious if it really works.  And if you have enough
different "known" signals present to create the graph.

Huw Powell

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