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constant 5 volt signal graphed even though the signal is changing as a function of time

This is (probably) a simple question but I am new to data acquisiton. I just need to acquire data on 4 analong input channels from 4 photodiodes that are turning on/off every 0.5 sec. I connected my circuit to the data acq card using an I/O connector card. My circuit is implemented on a breadboard. I am using LabWindows (sample programs) to collect information from the channels but the graph is showing constant 5 volt signals (for all channels) even though the voltages are changing. Any help or tips would be appreciated.
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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
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