Attenuation Probe DC Measurement

[David74]

I have read similar forum posts with similar issues, but I have not been able to find the exact answer to my question.  I am trying to read a DC signal ranging from 80V to 130V.  I have a NI 6124 simultaneous DAQ and a BNC 2120, which together are limited to +/- 10V, so I bought a TPI P250 differential probe.  It is a 100x probe and is rated for the volatges I am looking at and has a bandwidth of 250Mhz.

The probe reads both AC and DC signals accurately with an Agilent scope.  However, with my NI setup, AC signals are fine but DC signals saturate, i.e. the probe is not dividing the voltage.  I confirmed this by measuring some 9V batteries and the 100x probe read 9V.

Do I have the wrong probe?  Do I need to tune the capacitor?  

Let me know if I need to provide any more information.

Thanks

[Matt_L]

Hi David,

I saw that you also sent in an email about this, and what Josh said about the subject is correct.  The Multifunction DAQ devices aren't really designed for this, since they have high input capacitance and impedance, and these attenuating probes have high output impedance.  I would take a look at some of our Digitizer/Scope devices to meet your needs for this project.