Analog input range for PXI-6225

[jansiroky]

Hi there, good morning to everybody.

I would like to ask a question about PXI-6225 analog input. In thedatasheet there are shown accuracies for different analog input ranges. I can not find how to switch analog input range. Is it changed automatically? I would love to know which input range is ON to be able to calculate accuracy of my measuring set. 

If it is set automatically i wonder when does it switch the range? fe. in case of input of 0,9V, does the PXI card use range +-1V or does it switch to +-5V

Thank you a lot for any hint.

Have a nice day!

jan

[catarina · Accepted solution]

Hi, Jan

To get better accuracy of the measurement value, you can choose the analog input range.

If you use the LabVIEW, you can choose a maximum/minimum value in DAQmx Create Channel.vi like below (sorry, my LabVIEW language is Korean.)

If you set the minimum/maximum value, DAQmx determines channel gain. So, it can set automatically range. So, If you use the input of 0.9V, the DAQmx use range +/-1V.  

Please refer to this KB.

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z0000019N1OSAU&l=ko-KR

Thank you:-)

[jansiroky]

Hi catarina.

Thanks a lot for your reply. I do not use Labview, but VeriStand. But thanks to your answer i was able to find similar setting panel in Veristand System Definition File.

I attach screenshot for case, some one needs it.

Have nice day!

[TSE_Expert]

Hello Jansiroky,

there is no in situ automatic range switch. If you don't set the range explicitly, the device dependent default value will be used, for the 6225 it is +/-5 V. If the signal exceeds the set range, it saturates.

The following article is dealing with your question:

https://knowledge.ni.com/KnowledgeArticleDetails?id=kA00Z000000P8XxSAK&l=en-US

"When you specify a minimum and maximum value of -4 volts and 4 volts for an acquisition on most devices, DAQmx will automatically select a signal range of +/- 5 V and a device gain of 1.
When you specify a minimum and maximum value of 0 and 0.6 volts, DAQmx will automatically select a unipolar signal range of 0 – 1 V and a gain of 10. Using unipolar will keep the true resolution over this range. For example, in this example let's say your hardware has 16 bits of resolution. Your 16 bits will be across the 0-1V range, not the +/ 1 V range." 

Best Regards,

NI TSE

[jansiroky]

Definitely good to know!

thanks a lot.

j.