Voltage limits for USB-6289 Analogue voltage inputs

[kcop]

Hi, we are using NI USB-6289 to perform a test in our laboratory. We purchased these cards as we needed high resolution and high accuracy readings with a maximum voltage of 10V. Now the maximum test voltage has been changed to 13.5V and when we checked the specs sheet of these cards we noticed that the maximum working voltage is 11V. It also says that the maximum overvoltage protection is 25V for 8 pins simultaneously when powered on. Our test will have conditions where the cards are subjected to 13.5V on all pins simultaneously. There is no problem if the cards saturate at 10V, however we would like to be sure that this will not damage the cards.

We previously used the E-series DAQs which as explained in this link http://digital.ni.com/public.nsf/allkb/D46678951499D97D86256E47007478DD had a 25V overvoltage protection on all pins. We are unfamiliar with these new cards and would like to check whether there are any risks before connecting it.

[Kyle_A.]

Hello,

So you are correct in the specifications that you talk about in your email.  The working voltage is the voltage we specify our card to measure accurately, and anything outside of this specification will not be measured accurately.  The overvoltage protection states that for the USB M series board, you can put 25V on 8 lines simultaneously without damage, as you mentioned. 

For your application, if you plan to overvoltage all the lines, I don't believe this will be possible.  Did you use a similar USB E Series card before this?  Do you mind letting me know which model this is?  I have a feeling that since this new board is USB and not PCI that the overvoltage protection is different.

[kcop]

good morning,

The E-Series devices we used previously were PCI and not USB. The most commony used one is PCI-6033E.

[Kyle_A.]

Hello,

I believe this is the reason your previous cards had better overvoltage protection on them versus your newer USB form factor cards.  If there is a way to attenuate the signals before sending them into the DAQ, that may be your best route.  All other options would employ new hardware from what I can think of.  I hope for the best with your application!

[kcop]

Thank you for this advice,

However we have already tried this and there is little chance of attenuating the signals without introducing a significant amount of  electrical noise.

I have checked the different form factors of the 6289 board and found that the specifications for the overvoltage protection of PCI PXI and USB form factors are the same. Can you please recommend hardware with 18-bit resolution and protected up to at least 15V on all channels?

Thanks,

Karl

[Kyle_A.]

Hi Karl,

I was unable to locate a specific device that can handle the specifications you are asking for.  But what you can do is look into signal conditioning modules which can help measure higher voltage signals, and they will minimize the additional noise added to your system.  First, here is a reference to overcoming the voltage barrier on our boards, and it mentions to either optically isolate the signal externally or use SCXI/SCC modules to condition your signal going into the DAQ board.

For SCXI, going by your specifications, these two modules are what I found.  The 1104 can accept ±60V signals with a 2 Hz noise filter, and the 1104C can do the same but the noise filter is at 10kHz.  You would need additional hardware to use these modules, such as a SCXI chassis and cabling, and a mass termination device (PCI/PXI/some USB)

Other options would be to look at different cards with better overvoltage protection, but different specifications in regards to resolution, sample rate, and voltage specs.