Reading digital input from FP-DI-330

[Newbee2006]

I am trying to read the digital signal from the compact field point DI-330. Base on the documention comes with the module that both the INa and INb need to be connected for the NPN input device. However, no signal was read after connected the device per the documentation. Any suggestion?

[Jesse_O]

Hello Newbee2006,

I have taken a look at the documentation and I agree it is a little confusing.  If you look at the DI-330 manual, on page 9 you will find figure 10.  This figure shows how the channel is isolated and how the DI-330 functions.  From this diagram you can see that for the device to operate you need to turn on and off your power/current between the INa and INb pins.  I believe the only reason for connecting INa to your NPN device is to power it (based on the diagram in the manual).  Your external system just needs to turn on and off current that flows into and out of INa/INb.  Is your system doing this?  Can you measure current flowing into INa? 

Once you verify that your system is turning on and off the flow of current into INa I would then use Measurement Automation Explorer (MAX) to verify that the FieldPoint controller is reading this signal and transmitting it to the computer correctly.

Regards,

Jesse O.
Applications Engineering
National Instruments