Analog outputs cannot calibrate back to 0

[F. Y.]

Hello

Both USB-1080X analog outputs start to have an offset of about -0.003V. In the DAQami software, for example, I set the AOUT1 to 0, but the two connected input channels read -0.003V. I can confirm this is an output issue with external multimeters. (See the first screenshot)

There's another problem that I think it's related to this one  - after executing the mcculw example codes like ULAIO01.py, the output voltage level always stays at the last data point. For example, if the last data point of the output signal from ULAIO01.py before I quit the program is -4V, then AOUT1 will stay at -4V even if no program is running whatsoever(confirmed with multimeters), and I cannot stop it unless I unplug the USB. That significantly affects data acquisition because the next time I use the device, the input terminals will read a peak of -4V at the beginning, not 0V. (See the second screenshot)

I'm using official software and python examples so I'm not sure how could that happen. 

So in short my questions are: how to calibrate or refresh the terminals to default? How do I do that in python so the device is released completely every time it finishes an execution, and output terminals are back to 0? 

Thank you

[DAQman]

The analog output accuracy is about 1.8mV plus 0.083% of reading. When set to 5.0 volts, the accuracy is 1.8mV + 0.9mV. When set to zero, if your multimeter reads higher than 1.8mV and is less than a year old, I can arrange for free factory calibration.  Otherwise, the USB-1808X fee is about $150.00. What is the make and model of your multimeter - I would like to check its accuracy too. 

As for calibrating the device yourself, Measurement Computing chose not to add calibration functions to the programming interface. Instead, you could do something simple like check the offset and adjust each setting by that amount in your code.

Regarding the Python example, it is normal for the analog output to remain set to the last value. If it is a problem, add the code to put it to zero before the program exits.