Frequency measurement on dvm

Thread Starter

vpoko

Joined Jan 5, 2012
267
I have a Velleman DVM890F multimeter and was playing around with the frequency measuring function today. To my surprise, I found that it worked if I used just one probe, whether the red or black. This is probably perfectly reasonable to everyone else, but I don't understand how can it detect the frequency without a complete circuit. How does it work? Thanks in advance!
 

Adjuster

Joined Dec 26, 2010
2,148
Perhaps the disconnected side had enough stray capacitance to ground to give a bit of input voltage. The input impedance of such a meter would be at least 1MΩ, and probably 10MΩ in parallel with maybe 20pF.

Depending in the input frequency, and the meter's sensitivity, the capacitance of the dangling lead to ground might do it, or even the wiring in the meter might.
 

hgmjr

Joined Jan 28, 2005
9,029
One thing is for sure, you will need to use both leads in order to yield the most accurate frequency measurement.

hgmjr
 
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