PXI5214 range selection

[kkwong]

Hi,

   I am using PXI5124 digitizer to capture signals.  We found that we could not set the vertical range less than 2Vpp.   We have tried in oversampling and normal sampling modes.  In the 5124 specificaion we should be able to set the range to 0.2Vpp to 10Vpp.

   We set the vertical range by setting the niScope_ConfigureVertical() in C++ . Then we read back the getting NISCOPE_ATTR_VERTICAL_RANGE.  We found the report vertical range is always 2Vpp when we set the range below 2Vpp.

   Then we tested the range by inputting a 4vpp signal wave to the channel. Based on the clipping, we determined the actual vertical range. We had the same results of 2Vpp range.

   For range larger than 2Vpp, it works fine.

Any suggestion?

[DFGray]

The NI-SCOPE driver, per IVI specifications, coerces an input range to the next highest available range.  You may be running into roundoff errors in setting the 0.2V range.  Try setting it to 0.1V.  If this fails, please post your code so we can take a look.

[kkwong]

I have already tried that. Whenever I set the range below 2Vpp, such as 0.2V, 0.4V, 1V range. The vertical range was still 2Vpp.

[DFGray]

Please post your code, or the relevant parts of it, so we can take a look.

[kkwong]

Attached please find the code. This is an example came with NI_scope.  The sampling rate is 10MHz.  Probe attenuation is 10.

Also attached xls file is the captured waveform by the program with ranges 0.2V to 10V.  Input signal was 5Vpp sinewave with offset 0V.  You can see that the signal clipped at +/- 1V for range 0.2V to 2V. 

Hope this help.

Thanks!

[kkwong]

Just a second thought, is that because the probe attuation set to 10 causing the problem?

[kkwong]

I just done a test.  It seems that we can only set the range below 2V range if we switch the probe to x1. For X10, the range can only be down to 2V. 

Can anyone confirm this?

Or is there any way to set the range below 2V for probe X10?

[DFGray]

That is correct.  The minimum range the 5124 can handle is 0.2V in hardware.  If you attenuate the input signal 10X (a 10X probe), the board still has a minimum range of 0.2V, but the signal is now ten times smaller, giving an effective range of ten times bigger, or 2V.  The driver does the math for you so you don't have to.