Different readings on ChA&ChaB - 4227

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BSI
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Different readings on ChA&ChaB - 4227

Post by BSI »

Hi,
I am working on an application where I need to acquire a given signal simultaneously on both channels A and B. I use a BNC splitter and BNC cables to connect to the digitizer. To test out the signal I apply a 5 V square wave on the split inputs.

I have noticed a discrepancy between the reading on both channels. Swapping the BNC inputs does not change the signals I am getting. I tried three 4227s, acquiring data using the SDK via LabVIEW, and also directly with Picoscope 6. Below is what I get:
Graph 1 shows difference between ChA and ChB, while Graph 2 shows the same signal with another 4227.<br />The third digitizer gave again another discrepancy more or less like the one on graph 1.
Graph 1 shows difference between ChA and ChB, while Graph 2 shows the same signal with another 4227.
The third digitizer gave again another discrepancy more or less like the one on graph 1.
I would expect the two channels to give me something very much identical unlike what I am seeing. Any idea?
Thx

Laurent

Martyn
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Re: Different readings on ChA&ChaB - 4227

Post by Martyn »

Would it be possible to post a psdata file for a single waveform for each of the examples. This will help us see the full settings for the scope.

Trace 1 does look as if it may be within specification so possibly no a problem. Trace 2 is more interesting and would require closer investigation, there may be an issue with this particular device.

Are you using terminators or direct cable connections ?
Martyn
Technical Support Manager

BSI
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Joined: Wed May 12, 2010 3:15 pm
Location: Canada

Re: Different readings on ChA&ChaB - 4227

Post by BSI »

HI Martyn,

Direct connection, no terminators. Swapping cable has no effect. Acquiring A alone, then B alone produces the same results as seen as when acquiring both channels: Channel B shows the same artifact.
Thx.

PS: away from my desk until March 15.
Attachments
20140307-0001_BSI Dual Channel.psdata
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Martyn
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Re: Different readings on ChA&ChaB - 4227

Post by Martyn »

Can you contact support@picotech.com we need to see device that gave Graph 2 back here as there may be an issue with it.
Martyn
Technical Support Manager

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