NI 9425 Digital Input Module

[RobF]

Hi, Could somebody please advise myself on the following: I am planning on using the c series module 9425 with a compact RIO to detect 24V DC signals from various devices. Can I simply connect the DI pin to the positive terminal of a 24V + supply and the COM pin to the 0V of the 24V supply? Will the card then detect when the voltage is turned on and provide a path from the DI pin too the COM pin thus compelting the circuit. Or would I have to connect to the card in a different way? Regards Robert Foat

[crossrulz · Accepted solution]

That module is made for 24V logic.  So yes, you can just hook up your voltage straight to the inputs.  It was provide a 30kOhm resistance to ground (input impedence in the spec).  It is generally not a good idea to count on a digital input to complete a circuit.  The digital input should be more of a sense.

[RobF]

Thank you for your quick reply, as you said the 9425 will be used as a sense input and will not be used to complete the circuit.