daq 6015, problem about sampling analogue signals

[DAQPad 6015, reading bad values]

We are using a DAQPad 6015 acquisition device to sample some analogue signals. But usually we can not read appropriate values. We are obtaining same values with VI logger or with the software which is developed in .NET by using your library, so we know that the problem is not related with software. When we try to read the values from a signal generator, we can acquire more correct digital samples, however when we connect a power supply instead of a signal generator, the device gives us some strange values. As i said, we just want to acquire and sample some analogue voltage values from a TTL analogue circuit by using analogue input channels of the device; could you suggest us an appropriate device configuration or connection diagram, please? I have to add that we can not use all ground modes (i.e. we can not select RSE terminal configuration since it seems unavailable).

[Elijah_K]

There are a number of troubleshooting measures to consider at this point.

When the 6015 driver (NI-DAQmx) is installed it also installs an application called Measurement and Automation Explorer.  This utility is desiged to help users test their hardware and the I/O on their device.  Please make sure you have the latest version of DAQmx (8.5) installed and open this utility.  Find your card listed under Devices and Interfaces, right click on it and select 'test panels.' 

When you are connecting a signal to Ai0 with the test panel running in differential mode, please make sure that you are using the pins for ai0 and ai8.  You can actually create an analog acquisition task in MAX and click the Device Routes tab at the bottom to see the necessary connections.  This will probably be pins 34 and 68.  Confirm that you've set the card up this way, run the test panel and let me know if you're still having problems.

If you still experience the same issue, could you reply with the actual values you're reading versus the values you're expecting?  What do you mean by 'more correct?'