How to block the DC coupling?

[1170]

I am using DAQ 6014, I use the DAQ_Start to scan the AI port and get the signal, but the signal has both AC and DC coupling. How can I block the DC coupling? Can I block it by software or only by hardware? I am using differential input connecting mode with no resistor. Do I need to add a resistor and a capacitor to block DC coupling?

[RIO-Todd]

The NI 6014 only allows for DC coupling and so both DC and AC voltages are passed into the board. You could perform the AC coupling in either software or hardware. You would have to write an algorithm for getting rid of the DC offset.

To create AC coupling in hardware, you would place a capacitor in series with your input. The document linked below describes this in more detail. I hope this helps.

What Are AC and DC Coupling?
http://digital.ni.com/public.nsf/websearch/0F81C33977056A7D862566F1005CAA71?OpenDocument

Regards,

Todd D.

[1170]

Thank you very much for your answer, because it is very useful. Can I also ask if I want to block DC offset in hardware. How to decide the value of capacitor? I think the capacitor will influence the input impedence, and then cause the noise on the signal?