Dear Experts,
I've just started to use an USB-6211 board for Linux and MacOS, with a MacBook laptop having Mac OS X 10.5.8 and NI-DAQmx Base 3.4.
I observe an erratic behavior. If an analog input and the AI SENSE channel are both connected to the ground, and acquiring in NRSE mode, sometime I observe a correct behavior, with readout values slightly fluctuating around zero. Anyway, often the readout oscillates for a few seconds between the max and min readout values, and finally stabilize either to the max or the min value (e.g. +/- 1.09). When the board behaves like this, I can revert to correct operations only after several attempts: providing input signals with a waveform generator, connecting again to the ground, trying with Linux on a desktop PC, changing the operation mode to RSE. Anyway, it is enough to slightly change the connections (e.g. moving to a different AI channel) to fall again on this bad behavior, which is not immediately reversible. In other words, the board behavior strongly depend on the past history of the board itself. It also seems to change if the laptop is connected or not to the line, but I could not definetly stabilize the board either with or without the connection. Also, just waiting for a warm-up time does not help.
When the board shows a proper behavior with grounded channels, sometime (not always) I can also correctly acquire input signals. Once this condition is reached, the device seems to not fall again in the unstable situation if the connections are not changed. Anyway, changing the connections can be enough to trigger again the bad behavior, and it is not enough to restore the previous connections to recover.
The device seems to be more stable if operated with a desktop PC with Scientific Linux 6 and NI-DAQmx Base 3.6. Anyway, starting from a bad behavior on my MacBook, I need several attempts to reach the correct operation.
Do you have any suggestion about the problems I'm experiencing?
Thank you very much,
Francesco Renga
