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ADC200/20 external trigger

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ADC200/20 external trigger

Postby Ian Malone » Fri Feb 11, 2005 10:33 am

We're using the ADC 200 with the PicoScope software for a (NMR) teaching experiment. The equipment being measured produces a 300ns synchronisation pulse for external triggering. This works when using short timebases, and it's possible to plug the pulse into an input channel and observe it. However we are looking at signals on timescales of up to 100ms (in some cases seconds), and in this case the system often misses the synchronisation pulse; whether it is plugged into the external trigger or the B channel. Using an analog scope confirms that the equipment is working properly. I'm convinced this is something to do with sampling rate, is there
anything I can do short of trying to lengthen the synchronisation pulse?
Ian Malone
 

Postby Sarah » Fri Feb 11, 2005 10:44 am

Hi

Thank you for your post.

It does seem that sample rate is the issue here.

You might find that increasing the number of samples per scope trace helps. You can do this via Setting | Options | Advanced.

Hope this helps

Best Regards
Sarah
 

Postby Guest » Fri Feb 11, 2005 11:38 am

Thanks for the reply. I don't seem to have that option (the software version is 5.08.6), but there is a similar "samples per scope trace" under file | setup | scope. I have tried increasing it to 1,000,000 (the maximum), which works at 1ms/div (I suppose about 20ns/sample) and just about catches the sync at 10ms/div.

I suppose this means the normal scope mode software isn't suitable for the unmodified sync signal. Would it be worth trying the "save to disc" trigger option?
Guest
 

Postby Sarah » Mon Feb 14, 2005 9:53 am

Hi

Thank you for your post.

The Save to Disk trigger option simply saves a file of the trace every time the trigger goes so it would not change the function of the trigger in any way.

The software you have is quite old, I would recommend upgrading to our latest - R5.12.0. I don't think this would however overcome the problems you are seeing.

It may be worthwhile lengthing the pulse if you have this ability.

Hope this helps

Best Regards
Sarah
 

Postby Ian Malone » Tue Feb 22, 2005 4:15 pm

Just to follow up: I'm now using a 74121 multivibrator to generate a 800 microsecond pulse from the sync signal and successfully triggering the Picoscope from that. (I understand this is similar to the triggering approach used in normal scopes)
Ian Malone
 

Postby Sarah » Wed Feb 23, 2005 9:54 am

Hi Ian

I am glad to hear you got it working :D

Best Regards
Sarah
 


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