DAQ-mx reading voltage when none present

[stephenb2]

I'm attempting to read a voltage from Dev2/ai8. The NI-DAQmx has nothing attached to it; it is fresh out of the box.

However, it reading 10.8V:

A second NI DAQ (NI USB-6343) is doing the same thing on analog input 8. 

Using the python library, I am also seeing an incorrect yet different reading:

import nidaqmx

with nidaqmx.Task() as task:
    task.ai_channels.add_ai_voltage_chan("Dev2/ai8")
    print(task.read())

5.458278351573151

Am I doing something wrong?