PCI-6259 able to change between bipolar to unipolar mode

[stoico]

I was wondering if the PCI-6259 or PCI-6254 was able to change from bipolar to unipolar mode. It looks like it has a bipolar mode +10V to -10V by default according to the datasheet, but it doesn't say if it can switch to a unipolar mode like +10V to 0. It says it has 7 ranges but they all look bipolar. I know some can switch between modes and if neither has these capabilities is there a card with similar capabilities that can switch or has unipolar by default.

[devchander]

Hi Stoico,

THe M Series cards ( PCI 6259/6254 belong to M series) offer only Bipolar Mode.

There were some E series cards ( For Ex: PCI 6070E /6071E) in which you could choose between Unipolar and Biplolar modes for AI channels

But the M Series Cards have better Absolute accuracy in comparison with E series cards

Here is the link to the specifications of M series PCI 625x Family: https://www.ni.com/docs/en-US/bundle/371291g/resource/371291g.pdf

And here is the link to the E series Card's specifications: https://www.ni.com/docs/en-US/bundle/370725c/resource/370725c.pdf

This should help you compare between both and choose better

Hope this helps

Regards,

Dev

[Mark_E]

Hi Stoico,

I just wanted to add one more piece of information for you to consider. Dev was right when he said that there were E series cards that supported unipolar ranges and that M series are more accurate (along with other benefits) than E series. The good news is that you can still have the accuracy of the M series and also get unipolar measurements with them.

To measure unipolar signals with M series cards, you choose the smaller range you want and provide an offset. This is done with the non-referenced single-ended (NRSE) mode. The M Series device measures the voltage of an AI signal relative to one of the AI SENSE or AI SENSE 2 inputs. This would be your offset voltage. See the M Series User Manual (chapter 3 for signal descriptions and chapter 4 for ground-reference settings).

I hope this helps you make the right selection.

[Joel D]

Am I correct in assuming that the M series cannot be put in a unipolar mode from 0 to 20V, as this would exceed the 11V maximum difference between AI+ and AI GND?

I would like to use the ADC capabilities for a signal that varies from 0-18V. I'm wondering if there is a way to configure the input references so that I won't have to do any biasing on the signal.  Any suggestions or workarounds would be appreciated. Thanks,

Joel

[MikhailK]

Hi Joel,

Yes, you are correct. You can do a unipolar measurement of 0 to 10V but not 0 to 20V. If you want 20V range you might want to do differential measurement of -10V...+10V.