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!
Frequency measurement on dvm
- Thread starter vpoko
- Start date
A uC switching a pin high and low with various delays. The meter says its range is 10-20,000 Hz, but I didn't measure through the whole range.
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.
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.
