dax

measuring 32 mhz signal with dual trace oscillioscope
« on: June 19, 2013, 11:19:25 PM »
I am measuring 32 mhz clock signal  of a oberheim  keyboard using my dual trace oscilloscope.  The crystal says 32mhz on it.  using a 100 mhz scope set to ac input . 

I am used to measuring sine waves and square waves through - input to output-  amplifiers as a probe but this is new grounds for me.  Usually have the chan. set to about 1 volt per division and 0.1 ms when doing so

Any tips on what  i am missing - or maybe the clock is dead and therefore why this keyboard wil not produce audio. 

thanks in advance


abbey road d enfer

Re: measuring 32 mhz signal with dual trace oscillioscope
« Reply #1 on: June 20, 2013, 04:52:36 AM »
I am measuring 32 mhz clock signal  of a oberheim  keyboard using my dual trace oscilloscope.  The crystal says 32mhz on it.  using a 100 mhz scope set to ac input . 

I am used to measuring sine waves and square waves through - input to output-  amplifiers as a probe but this is new grounds for me.  Usually have the chan. set to about 1 volt per division and 0.1 ms when doing so

Any tips on what  i am missing - or maybe the clock is dead and therefore why this keyboard wil not produce audio. 

thanks in advance
  32MHz clock means period is about 30ns. If you want to see the square wave, you have to set the timebase to about 10-50 ns/div.
With 0.1ms, you have about 3 000 periods per/div, which would result in be a very thick trace.
Then are you sure the probe does not perturbs the oscillator? The capacitance of the probe may be about 30pF, largely enough to shut the oscillator down.
You should use a VHF probe, with a 10:1 ratio that would be seen as about 3-4pF.

However you should see something; if you don't it may be that the oscillator is duff...or not.

And please, use the correct symbol, MHz not mhz.
Who's right or wrong is irrelevant. What matters is what's right or wrong.
Star ground is for electricians.

audiomixer

Re: measuring 32 mhz signal with dual trace oscillioscope
« Reply #2 on: June 20, 2013, 07:42:46 AM »
You might also find the waveform is rather sinusoidal then square at 1/3 of your BW (signal to BW)... but you should get something at least. I probed a 24.568 odd Mhz digital clock and had the same issue as described above - you definitively need to turn the probe into times 10 mode. in 'normal' times one mode most if not all scope probes are BW limited to something below 10Mhz - another thing to be aware of. and then you need to get ground right at the tip of the probe, otherwise it will affect the waveform display even more.

cheers,

Michael

Andy Peters

Re: measuring 32 mhz signal with dual trace oscillioscope
« Reply #3 on: June 20, 2013, 05:15:58 PM »
I am measuring 32 mhz clock signal  of a oberheim  keyboard using my dual trace oscilloscope.  The crystal says 32mhz on it.  using a 100 mhz scope set to ac input . 

I am used to measuring sine waves and square waves through - input to output-  amplifiers as a probe but this is new grounds for me.  Usually have the chan. set to about 1 volt per division and 0.1 ms when doing so

Any tips on what  i am missing - or maybe the clock is dead and therefore why this keyboard wil not produce audio. 

thanks in advance

Set your horizontal timebase to something on the order of 10 ns per box. 0.1 ms/box is way too big because the period of the oscillator is only 31.25 ns.

Set the 'scope input to DC coupled.

-a
"On the Internet, nobody can hear you mix a band"


 

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