Multimeter hookup for Duty Cycle

[SJ]

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. If the duty cycle of something is supposed to be 50% with the car at
800 RPM . . .and you read 4.0 volts on your meter . . . you have yourself a
calibrated point for that measurement. If you can get another reading . .say
like a 25% duty cycle  . .and get another meter reading . .. you now have
two measuring points. With two points you can make a line on a graph . .
duty cycle vs voltage. Using this chart, you can interpret any other voltage
reading and determine the duty cycle.

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.

I like multitasking tools.


SJ
85 Dodge PU, D-250, 318, auto
85 4k - - sold but still on the road
88 5kq
90 100q



> Message: 20
> From: Ti Kan <ti at amb.org>
> Subject: Re: Multimeter hookup for Duty Cycle
> To: CTDiesel at aol.com
> Date: Sat, 3 May 2003 16:38:31 -0700 (PDT)
> Cc: quattro at audifans.com
>
> CTDiesel at aol.com writes:
> > Can someone tell me how to or if its possible to hook a multimeter up to
the
> > test connector in the engine compartment to test duty cycle or dwell?
The
> > Fuel Injection and Engine Management books show that you can.  Do you
hook it
> > up in series or like your checking for continuity?
>
> Only multimeters that have an explicit duty cycle function can be
> used as such.  Many multimeters can only measure resistance, voltage
> and current, but not duty cycle.  For those that could measure duty cycle,
> you hook it up like you would checking voltage.
>
> -Ti