That explains the funny readings at my bench, when my mill is running or the LED - benchlight is running.
I always thought some of the EM-crap is inducting into the unshielded wires.
Interesting, can you reproduce it?
My DMM don't show that stable value like yours when influenced by EM.
The value is dancing around by several 100mA in a random pattern.
The LED light is a simple 12V LED-strip glued on the shelve, powered by an cheap switching suply.
The distance to the DMM is ca. 1m.
The mill is powered by a 2 KW HF spindle at 400VAC at maximal 400Hz Sinus
(I don't knew the internal switching frequency of the U/f converter.)
The axes are driven with 46V stepper motors.
The distance to the DMM is ca. 3m to 4m.
I thought this readings are normal in this dirty environment.
At the moment I sadly have no other DMM to double check.
My cheap arse fluke branded one is slowly dying on me after 15 years. (Its build quality is quite 10€ china-like)
I thought about a new EEVblog-Brymen one as a replacement, but sadly I can't get one on Amazon (Europe) and the shipping costs from Australia are quite high.