Does LabVIEW Realtime 7 support the PXI-4070 FlexDMM?

[Nabil E.]

I need to take high-accuracy RMS measurements and also capture transients (not simultanously). The PXI-4070 FlexDMM looks like the perfect instrument to use in this application, as it has two modes: high-accuracy RMS and high-speed digitizer. However, the catalog does not clearly indicate whether it's supported under Realtime. If it's not, what else can I use? Application is somewhat time-critical - can't simply use a Windows machine. The signal levels range from a few millivolts to 250V AC RMS.

[Claudia]

Hi Nabil E.

It does seem like the PXI-4070 FlexDMM fits all the requirements of your application. I have a couple of ideas, but I first need to learn more about your application and the time-critical parts of it.

I would appreciate if you could give me a call. Just call 1-800-433-3488 and ask for me.

Claudia Lorente
DMM PSE - R&D
National Instruments

[Claudia]

Hi Nabil E.

We recently released NI-DMM 2.3. This version of the driver adds support for the NI 4070 and NI 4072 FlexDMMs under LabVIEW Real-Time 7.1.

You can reach all current versions of our drivers, including NI-DMM 2.3, by going to www.ni.com/downloads and clicking on "Drivers and Updates >> Current Software Versions".

Claudia Lorente
National Instruments

[Nabil E.]

Claudia,

I have been using the PXI-4070 under RT 7.1 for about 6 months. I actually have 3 of them in one chassis. I am very pleased with the suitabilitly of this configuration for my application. However, I see room for improvement.

My application requires that the three DMM's aquire data simultaneously when in the digitizer mode. By simultaneously, I mean within no more than a few hundred nanoseconds. What I tried at first is to trigger the 3 DMM's simultaneously using a clock from a DAQ board (actually an M-series DAQ). This proved to be insufficient because the trigger latency and the trigger jitter of the 4070 exceeds the limits dictated by my application. I found myself having to resort to a 14-bit simultaneous-sampling card, the PXI-6132. This card did the trick (1 nsec interchannel skew!) but only when the voltage level was within its range (roughly 100 millivolt to 10 volt peak in my exprerience). I would have used the PXI-6120 which has more ranges; however, it's more costly, slower, and its input impedence is relatively low (1 Mega Ohm).

It would be neat if the new 4071 would support tighter triggering. Specifically, I would be thrilled if multiple PXI-4071's that are installed in the same chassis could somehow share the same clock.

Regards,
Nabil