True bipolar voltage measurements with USB 6008/6009

[fish8100]

Can either the 6008 or 6009 be used to make true bipolar (positive and negative voltages referenced to GND) measurements???  If not, what is the least expensive DAQ solution with this capability???

Thanks.

[Dennis_Knutson]

Have you read the manual that comes with the 6008/6009? What is confusing about the single-ended configuration and spec?

[fish8100]

My request for verification was motivated in part by a competitor's product.  They make references to pseudo-bipolar and differential signal inputs.  Since true bipolar signal measurements are critical for my application, I wanted to be ABSOLUTELY sure that the 6008 and 6009 products could do this.

Your snarky response was NOT helpful.  A simple YES or NO was all I was after here.

[Dennis_Knutson]

Rude responses aside, you made absolutely no mention of a competitor, psuedo-bipoar, not the fact that you had actually read the manual. Your question was very incomplete and I posted a legitimate question to you. It was not all snarky. Would you like a link to how to properly post a question?

[fish8100]

Maybe you should go back and re-read my original question.  It's a simple YES or NO question- and you still haven't answered it.  Assuming you work for NI, your attitude toward a prospective customer is convincing me to give more consideration to the competitor's product.

[Dennis_Knutson]

Why would you assume I work for NI? And why are you confused by the simple explanation in the manual? If you have any electronics experience at all, you would understand that a RSE connection has a measurement range of +/-10 volts referenced to gnd. That is the description in the manual and hence my question about whether you read it.

[SnowMule]

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@Dennis Knutson wrote:

Have you read the manual that comes with the 6008/6009?

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^ This.

Page 18.

[Sean_N]

The short answer to your question is NO, the 6008/6009 does not do true differential.  The device multiplexes through the channels and in software measures the difference to the ground of each channel.  A true differential device will use a differential amplifier which does not allow single ended measurements.  The most cost effective device is going to be a cDAQ module (which you would of course need a cDAQ chassis).  Something like a NI 9215 would work.  The cheapest PCI card starts around $2000, where as, you could get a chassis and module for around $1200.  I hope this helps!

Thanks,

Sean

[John_P1]

Actually, the 6008/6009 does support differential as well as RSE measurements.  The multiplexing of the channels doesn't change the fact that the measurements are differential.

Some other NI products (namely, many S Series DAQ devices) support "Pseudo-differential", which means that the (-) terminal does not have the full bandwidth of the (+) terminal.  This is not the case on the 6008/6009.

Now, I'm not sure what capabilities you are looking for exactly, but by the standard definition the USB-6008/6009 supports true differential measurements.

Best Regards,

[John_P1 · Accepted solution]

The question of unipolar vs. bipolar vs. pseudo-bipolar also was mentioned in this thread.  The 6008 and 6009 use bipolar mode only, and support differential or rse input configuration.  Please note that {unipolar / bipolar / pseudo-bipolar} is independent of {differential / rse / pseudo-differential}.

The 6008/6009 does not use "pseudo-bipolar", which would mean that each differential input must be positive with respect to ground.

Best Regards,