ASCII Data from Tektronix DPO 4000 Series

[_natalie_]

Hi again,

Earlier I asked about how to get data from the oscilloscope so that later it can be saved as a csv file to a remote computer.  I was directed to look at the Transfer Waveform Data from the Oscilloscope.

I followed the tests and I used the CURVe? query to get the ASCII data.  

The output can be something like this as a string:-110,-109,-110,-110,-109,-107,-109,-107,-106, -105,-103,-100,-97,-90,-84,-80

These aren't ASCII values that I recognize especially since there is a negative sign.  Does anyone know how to convert this back using LabVIEW?

Thanks!

[billko]

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@_natalie_ wrote:

Hi again,

Earlier I asked about how to get data from the oscilloscope so that later it can be saved as a csv file to a remote computer.  I was directed to look at the Transfer Waveform Data from the Oscilloscope.

I followed the tests and I used the CURVe? query to get the ASCII data.  

The output can be something like this as a string:-110,-109,-110,-110,-109,-107,-109,-107,-106, -105,-103,-100,-97,-90,-84,-80

These aren't ASCII values that I recognize especially since there is a negative sign.  Does anyone know how to convert this back using LabVIEW?

Thanks!

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Usually the manual will tell you what the output means.

[Joannick]

I think it could help if you show the vi you are using, or at least a screenshot. I can't garantee it will lead to an answer.

[Kyle97330]

That scope uses an 8-bit analog to digital converter and it's giving you the raw outputs of that.  So the smallest value your scope can read with its current scaling and offset is -128 and the highest is 127.  

I recommend you download the Textronix VISA drivers and either use them, either instead of your own VIs or as a reference for interpreting the CURVE? command.  But basically, they get the XY increments, origins, and offsets with:

WFMP:XZE?;:WFMP:XIN?;:WFMP:YMU?;:WFMP:YOF?;

[ben64]

Have a look at the WFMInpre:YZEro command in the programmer manual, the formula to convert the CURVE? query results is given in this section.

Ben64

[TTman]

Hi,

I know this is very old thread. Just for the heck of it who knows someone want to know what they are. I hope you found the answer. What you see are points or positions on the screen of a scope. You can use that to convert to a voltage amplitude. For example, 0 point is a the center of the screen. positive points are at top side and negative points are below the 0 reference. 127 is at the top edge and -127 is at the bottom edge. To figure out the voltage at each point you need to know the vertical scale setting on the scope and the offset.  For example, let say the offset is 0 and your vertical is .5v/div and you have a point at 120.

1. convert to volt per point and most scope have 10 divisions with 0 at center.

  .5v/div x 5 div = 2.5 v for total for the positive side

2. find out for volt per point

  2.5v/127= 0.019685 v/pt 

so 120 pt  x 0.019685 v/pt = 2.3622v

Note, horizontal points are more constant. it changes with s/div.

Hope this helps!

[crossrulz]

I'll just drop this code here for how I get the waveform from a Tek oscilloscope.

Note that I prefer to get data out in the binary format as it is more compact.