Vertical offset using the TDS2024B IVI driver

[Mister_Rose]

I plugged in a USB Tektronix TDS2024B scope and I am trying to test the IVI setup and connection with the  example program "IviScope - Acq Wfm Edge Triggered.vi".

The problem I am having is I cannot set the vertical offset to anything other than 0.

I am testing with the 5V 1kHz square wave coming in and when I try to set an offset, I get an error. Can someone explain why I cannot change the offset? Does this impact the precision of the waveform coming out of the scope?

If I want to analyze the waveform and I cannot adjust the offset, I will have to adjust the range so that it all fits in. This may dilute the precision of the measurements.

IviScope IVI Error Converter.vi<ERR>
Primary Error: (Hex 0xBFFA0010) Invalid value for parameter or property.
Secondary Error: (Hex 0xBFFC0004) Parameter 4 out of range, or error occurred while setting Parameter 4.
Elaboration: Offset


<b>Complete call chain:</b>
     IviScope IVI Error Converter.vi
     IviScope Configure Channel.vi
     IviScope - Acq Wfm Edge Triggered.vi

[NathanT]

Hello Brian,

       I see the same issue with a TDS2014B, so debugged into the IVI Specific driver with CVI and found out that the range table for the Offset attribute was causing the problem.  It was configured to only accept "0" as the offset.  I have made a temporary workaround by changing the range table to accept -10 to 10 V, so you will need to do the necessary calculations to determine what the actual range for the offset is.  I have attached the updated dll, please replace the one on your system and give this one a try.

       We will work on a more permanent solution that implements the correct calcuations.

Cheers,

NathanT

[Mister_Rose]

How long before the permanent fix is released? I have time to wait for the final version, as long as it isn't months away. And I can live with the limitation, for now.

[NathanT]

Hello Brian,

        We are pretty busy, but can hopefully have the permanent fix released by the end of the month (possibly sooner).  What is interesting is that you are the first person to notice the issue in the 7.5 years that the instrument driver has been released.

Thanks,

NathanT

[Albert.Geven]

Hi Nathan

Maybe more people use the LabVIEW drivers instead of IVI

[NathanT]

Hi Albert,

       That might be the case, or getting the maximum precision might not be a primary concern.

-Nathan

[BrandonSun]

Hi Brian,

I took a look at the user manual of TDS2014B but failed to find any content about Vertical Offset. It seems to me that the instrument does not support Vertical Offset concept. It only supports waveform positioning (horizontal/vertical), and the positioning just affects how the waveform gets displayed on the screen, but it does not impact the value it measured, neither impacts the Vertical Range.

The Vertical Offset parameter in ConfigureChannel actually will set the VERTICAL_OFFSET attribute defined in IviScope class specification. And this attribute emphasizes the ability to change the data measured with respect to the current Vertical Range. Since the device does not actually support Vertical Offset, so the driver always accepts and returns (if you query the attribute) zero value for Vertical Offset.

To rectify the waveform position on the screen, you have to use the property node and set the value of Vertical Position.

We may revise the driver to remove the restriction on only accepting zero value so as to make the it more robust, but again, configuring Vertical Offset will not affect the data measured.

Hope this helps.

Regards,

Brandon 

[A.Boone]

Has anyone got a fix yet for this issue. I am using x1 probes and need to measure 30V so need to move the channel trace down to enable this to fit on the display and also to measure properly. Any help greatly appreciated.

[Jake_G]

After going through the example, it looks like the VERTICAL OFFSET is just going into a VI that has a Call Library Function Node, so I believe that the above statements show that changing the value is outside the parameters of the USB device.

[Mister_Rose]

<I>After going through the example, it looks like the VERTICAL OFFSET is just going into a VI that has a Call Library Function Node, so I believe that the above statements show that changing the value is outside the parameters of the USB device.</I>

I can send SCPI commands to reposition the signal. This feature does not seem to be present in the IVI driver, though.