Using a 100x Probe with NI-6120 and BNC-2110

[montyq83]

Currently I am acquiring data using the NI-6120 with the BNC-2110. We know that the voltage limit for the 6120 is +/- 42 volts and are acquiring voltages up to
+/-200 volts. We put a 100x probe on the BNC-2110 to essentially get  ++/-2 volts but on the computer our graphs is showing the peaks of our sine wave is
0.9-1 volt. Is there something we are doing wrong? I believe it is single ended. Here is the model of the probe I am using. Tektronix P5100 2500V 250 MHz Oschillscope Probe. I am using the DAQ Assistant vi if that helps as well.

[Ima U]

Hi montyq83,

Here is a helpful Developer Zone article on AC Measurements.  It gives tips on performing AC measurements and different approaches.  Make sure the frequency you are sampling is not out of the bandwidth for your probe.

In the DAQ assistant you can change from Differential to RSE or NRSE.  Remember, it is not reccomended to use RSE if you have a grounded signal source.  Double click on your DAQ assistant to open it and change the terminal configuration.

Message Edited by Ima U on 10-22-2007 05:39 PM

[ChrisR.]

I suspect the combination of the BNC-2110, cable, and PCI-6120 present too much capacitance to properly compensate your scope probe. From this page: http://www.tek.com/site/ps/0,,56-10262-SPECS_EN,00.html I see that the probe you're using is designed to work into a load of no more than 30pF.

In addition to having too much capacitance, your setup doesn't have the 1M resistance to ground that a scope probe needs to work properly. Here's an article on attenuating probes: http://zone.ni.com/devzone/cda/ph/p/id/17 Unfortunately, NI's DAQ products aren't designed to work with these. The digitizer products are.

Chris