# Measuring low frequencies with PicoScope/multimetre

#### Jack Tranckle

Joined Jan 20, 2016
73
I have measured the frequency of a music synthesiser at different notes but seems to get slight error that the lower frequencies. the PicoScope seemed to take a while to settle to frequencies below 80Hz and sometimes crashed. is the picocope giving accurate readings at this low frequency? would a multimeter be better and measuring at lower frequencies ?

Joined Mar 10, 2018
4,057
What model Picoscope do you have ?

What does the manual say lower limit on freq counter is, if any ?

Regards, Dana.

#### Hymie

Joined Mar 30, 2018
1,091
Besides checking the instrument specification (as danadak says), in my experience audio signals (with their inherent harmonic content) can easily fool a frequency measurement.

If the picoscope is displaying the waveform, you could measure the period and check that it is displaying the correct frequency value.

Be aware that when using a scope to measure a waveform frequency, changing the time-base can alter the result – you need to ensure that the sweep rate is appropriate for the waveform to get a valid result.

#### Hymie

Joined Mar 30, 2018
1,091
One other piece of advice, make sure that you have a stable waveform displayed (triggering reliably); since you are only interested in frequency (and not voltages) try both ac and dc coupling of the signal, which may make a difference.

Joined Mar 10, 2018
4,057
Some DSOs AC couple the freq cntr chain input, so there is a lower limit
on what can be measured.

Regards, Dana.

#### Janis59

Joined Aug 21, 2017
1,482
My picoscope is 6404C what is rather rich-endian. I never cached anything similar, but always I had been interested in rather high not low frequencies.
Thus, probably cheaper models may lie? Because generally, as more to give it time to breath as more exact ought be reading. If Your case says contrary, then SOMETHING may had went wrong.

By the way, try to use a time interval reading instead. Or use the ordinary frequency meter....
However, if the aim was musical instrument adjusting, may be warned that there exists a plenty of different note scales, the electronic, the absolute, the ralative, the string etc etc And all them diifers with +/- dozen of Hz.
And last idea, install the PC Zeitnitz scope, where You can use the built-in generator. To cach a interference betwen two frequencies You may with some few Hz exactness. And if generator is same exact as PC quartz, then such measurement will be rather precize.