LabJack U6 Pro (and others) self-test script (#P53)

On the eternal quest of de-cluttering the living room, I picked up a bunch of stored “defective” LabJack units the other day. These are USB DAQ modules with generally very decent specs, in the case of the U6 Pro a 24bit (22bit effective) DAC with 14-port multiplexing (so 14 analogue ports, or 7 differential analogue ports), fixed 10µA and 200µA sources, two 12bit DACs, internal temperature…