Doepfer

I had a question about my new Velleman Panelscope which I've managed to hook up to my modular using the 197-2.

I'm rather new to oscilloscopes and I was wondering should I expect it to be able to tell me the frequency of a slow-moving CV.  I'm not seeing a way to read the frequency of a wave.

thanks,

Bryan

Hi Bryan,

> I'm rather new to oscilloscopes and I was wondering should I expect 
it to be able to tell me the frequency of a slow-moving CV.  I'm not 
seeing a way to read the frequency of a wave.

As long as your slow-moving CV is actually repetitive, then you 
should be able to do it by measuring the time it takes for the 
pattern to repeat. I don't know what facilities that scope has, but 
often scopes have cursors you can move around the screen, and it will 
tell you the readings of where they are, and then take the 
difference. If not, then you will have to judge it for yourself, from 
the timebase setting of 'so many seconds per division'. Do this at 
two points where the pattern repeats, for example the peaks, or where 
the wavefrom crosses the zero line *in the same direction*: this is 
called the 'period' of the signal. Then simply divide this into 1 to 
get the frequency, so frequency = 1/period.

Try it on something you know first, to check that you have the hang 
of it, for example, for middle C coming out of one of your 
oscillators you should see the time difference as about 0.0038 
seconds = 3.8 milliseconds, so 1/0.0038 = 263Hz (middle C actually 
261.63Hz). For a slow moving waveform it is likely that you will have 
to 'freeze' the display after one pass to be able to make a 
measurement if the timebase is set very slow.

Tim

> I had a question about my new Velleman Panelscope which I've
> managed to hook up to my modular using the 197-2.
>
> I'm rather new to oscilloscopes and I was wondering should I
> expect it to be able to tell me the frequency of a slow-moving
> CV. I'm not seeing a way to read the frequency of a wave.
>
> thanks,
>
> Bryan

You cannot read the frequency from an oscilloscope directly. You have to
measure the period (P) of the waveform (i.e. the time difference between two
peaks or two zero-crossing points) and then calculate the reziprocal value f
= 1/Q. For example if the period is 0.2 seconds the frequency is 1/0.2 = 5
Hz.

There are more expensive digital scopes available that do this job for you.
The frequency is measured by means of two cursors which are manually moved
to the peak or zero-crossing points mentioned above. From the currently
selected time base of the scope and the difference between the cursor points
the frequency is calculated and displayed on the screen. Even scopes with
built in frequency meters are available but these are actually two different
devices built into one case.

Best wishes
Dieter Doepfer