using a volt meter to measure duty cycle
using a volt meter to measure duty cycle
(OP)
Is there a simple way to use a volt meter (DMM or analog) to measure duty cycle? Assume the input is very clean -- steady and "rail to rail" signalling. Duty cycle is then just the time average of the input divided by the supply voltage.
My gut tells me there ought to be a simple way to do this. Would an analog meter automatically do it (just divide the meter reading by the supply voltage)? Would a DMM do it itself, or would it need some "help"?
Cheers,
circuitmangler
My gut tells me there ought to be a simple way to do this. Would an analog meter automatically do it (just divide the meter reading by the supply voltage)? Would a DMM do it itself, or would it need some "help"?
Cheers,
circuitmangler





RE: using a volt meter to measure duty cycle
RE: using a volt meter to measure duty cycle
RE: using a volt meter to measure duty cycle
Are you looking at a fixed frequency or does it vary? What kind of accuracy do you want? Do you need to calibrate this or is some quick and dirty/cheap solution adequate?
OperaHouse and felixc have some good suggestions. You might also consider a monostable multivibrator if the source can't take the loading of felixc's suggestion.
If you are considering buying a new meter anyway, some DMMs have frequency/period/duty cycle functions included.
RE: using a volt meter to measure duty cycle
The frequency will change but only when I deliberately
change it, so t would be nice if I didn't have to re-tune
the circuit every time I changed the frequency, although I
wouldn't mind hitting a "reset" button or some-such. Or if
the circuit could average over the last N seconds for some
small value of N.
I've looked into DMM's that have duty cycle capabilities,
but I really can't justify the expense right now. I'm just
looking for something really cheap so I can get a rough idea
of what the duty cycle is (say, to within +/- 5%).
Thanks again for the suggestions.
RE: using a volt meter to measure duty cycle
If your input signal is a pulse and you know it's peak voltage and it's frequency is below the filtering rate of your DMM, then you can measure the duty cycle by your volt meter.
_V1_
| | |
| | __V2__|
<-t1-> <-t2->
Due to above values and asume that VDC is the displayed value on the volt meter, we have:
VDC=((V1*t1)+(V2*t2)/(t1+t2))
if V2=0 then VDC=V1 * t1/(t1+t2) where t1/(t1+t2)=Duty Cycle
Hence:
Duty Cycle= VDC/V1
and Duty Cycle% = (VDC/V1) *100
Best regards,
Kasra Ravanbakhsh
Email: info@kdi-co.com
Web: http://www.kdi-co.com
RE: using a volt meter to measure duty cycle