Author Topic: Using 2 scopes for 4 channel measurement  (Read 1342 times)

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Offline Harvs

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Using 2 scopes for 4 channel measurement
« on: May 21, 2013, 02:24:15 pm »
I picked up my new scope today and thought it was a good time to break out the programming manual.

I did some tests feeding the trigger out of the DS2072 into the external trigger and channel 1 of the DS1052, and got a trigger delay of 210ns +/- 5ns across all time bases on both scopes.  So I though that wasn't too bad, the trigger delay could be corrected for, so it just leaves the uncertainty over +/-5ns.

So I learn't a few SCPI commands (I never realised it was as easy as it is,) and hacked together a quick piece of test software to see if the concept was going to work.  I recon it worked ok, and it'll be easy enough to write an SPI decoder for it.  The screen shot attached was using a 200kHz SPI bus that's driving a DAC.  Both 2nd channels of the two scopes are capturing the same clock signal to show the channel alignment.

 

Offline free_electron

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Re: Using 2 scopes for 4 channel measurement
« Reply #1 on: May 21, 2013, 02:54:51 pm »
yep. that works fine. i used to do that with two 54645d's. that gave me 4 analog and 32 digital channels. ideal to debug a huge fpga.
i had the fpga actually generate a trigger signal and both scopes looked at that. zero delay
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Offline marmad

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Re: Using 2 scopes for 4 channel measurement
« Reply #2 on: May 21, 2013, 02:55:36 pm »
I did some tests feeding the trigger out of the DS2072 into the external trigger and channel 1 of the DS1052, and got a trigger delay of 210ns +/- 5ns across all time bases on both scopes.  So I though that wasn't too bad, the trigger delay could be corrected for, so it just leaves the uncertainty over +/-5ns.
There's a mini-discussion of the Trigger Out at the Rigol DS2000 thread (starting here). BTW, the trigger delay when using the External Trigger is slightly less: ~163ns +/- 4ns (of jitter) - see image showing 8x 250ps jitter.

These delay times (~160 and 210ns) are not very good, IMO, and rather a disappointment of the DS2000. I think a typical Trigger Out delay should be closer to 50ns maximum - and certainly with less jitter.
« Last Edit: May 21, 2013, 02:57:37 pm by marmad »
 


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