This nice instrument was given to me as being a power supply. In real it is a Voltage/current standard for calibratring multimeters. It comes from the Philips service centre in Eindhoven. It is probably from 1974.
It is programmable. So you can hook up a meter and run a program. That is handy if you are doing series of meters. I do not do that so I never tried that function.
The display is great with those huge nixies.
– CMR 100dB (50Hz), 140 dB (DC)
– 0-1199.999V in 4 ranges, max resolution 1 uV
– Tempco at 23 +/- 1 C and 70%RH is 0.0003%/C
– 24H accuracy 0.0015%, 3 months accuracy 0.004%
– linearity: deviation less than 0.0003% of range
– 0-119.9999mA in 4 ranges with 1nA max resolution
– 24H accuracy 0.005% , 3 month accuracy 0.016%
The value you dial in is tranferred in BCD and a PWM modulator turns it into a AC level and that is tranferred into a DC level.
I have the full manual and schematics including handwritten papers about production. The unit is original a Takeda Riken Industry CO ltd. Model TR-6120 but relabled by Philips. The notes are hard to read but it looks like it is about changes for the Philips version.