Hi,
I bought a second hand Rohde & Schwarz NGMO2 power supply. It's a nice two-quadrant (lab) power supply, 0..15V up to 5A, dual channel. Low noise/ripple, accurate and fast. It can act as a current sink, record measurements, is programmable, can trigger on inputs, etc etc. The fact that there are no binding posts in the front is slightly inconvenient, but I'll sort that out. At least the fans aren't very loud.
thmjpr did a teardown and description in this thread:
https://www.eevblog.com/forum/testgear/ngmo1-0-15v-0-2-5a-power-supply-teardown-%28rohde-schwarz%29/msg237280/#msg237280. My unit appears to be exactly the same, except it's the two-channel version.
I've been testing it today, and it seems to work pretty nicely, and the voltage & current settings & measurements seem pretty accurate (as far as I can trust/compare with my humble EX330 & DS1074-S anyway.
However, because it has a whole bunch of analysis/measurement options, it also has an extra DVM option where each output channel has an
additional digital volt meter input, i.e. separate from the sense input. THAT function appears to be way off in my unit.
When I measured over the full range on both channels, both seem to consistently read at 183% of the accurate value. Seeing as both channels have completely independent hardware, I imagine this is just some wrong calibration setting/value in the unit (last cal: March '07), and not a hardware issue. This suddenly also explains the "CALIBRATED: RESTRICTED USE" sticker on the unit.
Apparently I can recalibrate the unit using either the front panel unit or remotely (RS232/GPIB), but the procedure is only described in the service manual which I don't have. I'm afraid that if I start the procedure now and can't properly do what it asks, it might screw up the current settings that
are correct. And then it probably wouldn't just be this "bonus" DVM function that's way out.
Does anyone have information about the calibration procedure for this unit perhaps?
Thanks!