First lets see if you can see the signal in Measurement & Automation Explorer (MAX).
MAX should have a shortcut your desktop. Double click on MAX; expand the devices and interfaces option; expand the traditional NI-DAQ Devices.
Right click on your device and choose "Test Panel". You can test the channels here. Choose continuous mode as the Data Mode and click on start.
If do not see the signal that you expect, check your connections. Use an oscilloscope to check the signals being sent out from the photodiodes.
If you do see the signal, then you have connected your signals correctly. Which sample program are you running? Also which CVI, NI-DAQ versions do you have?"
Penny