NI Scope Vertical Range Issue

[somit]

Hello,

I am using the NI-Scope Fetch forever VI to fetch and display data from my PXI-5105 ADC card. I have hooked up a sine wave to the channel input of the ADC. The sine wave oscillates at +/- 3V. However, I have set my vertical range to 2V, which I believe implies a vertical range of +/- 1V.

Why do I not clip the sine wave? I thought that setting a 2V vertical range would clip at the voltage boundaries. Please see the attached screen shot.

-Somit

[David S.]

Hi Somit -

The 5105 has four valid ranges for 50-ohm/1-Mohm input:  0.05, 0.2, 1, and 6 Vpp.  (There is also a 30Vpp range for 1-MOhm input.)  When you select a 2 Vpp range, the hardware chooses the 6 Vpp range to accommodate this.  In this range, the input signal isn't clipped by the ADC.  Since the driver software isn't meant to clip the signal artificially, you retrieve data from the device in the full range.

Here is the spec sheet for the 5105.  Page 2 shows the valid Full Scale Input Ranges.

If you want to artificially clip the data in software, you can simply use the In Range and Coerce VI on the waveform before displaying it.