If it's just the state of the relay you want to read you can use digital-out to digital-in.
But, be sure that the relay contact work at low current
Make one digital output high and feed that output voltage to your contacts. Wire the other side of your contact to the digital inputs.
Inputs have a weak pull-down so a open contact is a '0' at the input and a closed contact a '1'
No, if you have a relay that is specified for currents like 5A they can have a minimal current for the contact to work. Below that minimal current the manufacturer won't guarantee that the contact will conduct.
This way of testing the current will be lower then 1mA. Or add a resistor at the input to get more current through the contacts.
Again if you have small relays it should not be a problem. Check the datasheet of the relay.
OK, just mentioned it to be sure.
Good luck with your project. Funny at this moment I am also working on a test for a relay module.
Using a PXI-6251.
Message Edited by K C on 05-23-2007 04:33 PM