Measuring Frequency? (Probe tip)

On another thread there was some discussion about how to measure the frequency of a single-sided signal that didn’t cross “zero”, for example the ~0.5 kHz waveform shown below where the scope can’t lock on to read the frequency.

The tip here is to add a small capacitor in series with the probe tip. This will cause a voltage shift thru the capacitor such that the meter will see a zero-crossing and can count the pulse train. Depending upon frequency the cap value can distort the signal shape so it will need to be selected somewhat based upon the expected range. Start with a low value (eg 47pF) and work up (100nF) if no distortion is desired, but to measure frequency only it won’t matter. This is with 1uF.

when the frequency was increased to ~50kHz, then the 1uF was too large and slowed the response, so in that case a lower value was needed to square it up.