It seems that everything is circular - ingenious electronics to calibrate other ingenious electronics. What's the practical use for this generator other than calibrating other test equipment?
At this sort of resolution accuracy, yeah, that's pretty much the case.
Something like the constant generator is handy for testing LED's for example, but of course the need for this precision is quite niche.
Many of us on here are obsess... err... I mean, interested in high precision gear. It can be a sickness, you have been warned!
Precision current sources (0.02% uncertainty/stability) are needed for thermometry, i.e. precise measurement of temperatures, especially in physics experiments at very low temperatures down to liquid He4 @ 4.2K and below.
For PT100 sensors, precise 1mA or 100µA are needed, 10µA and 1µA for Diode based thermometers (e.g. from Lake Shore) and for NTC types as carbon resistors. All that requires 4 point Kelvin measurement, and offset compensation, i.e. a setup with an external current source and a DCV multimeter.
The programming feature of the current source can be used to switch the current off, measuring the thermal offset, which would then be substracted from the measurement with current applied. Very few DMM have this feature, called Ohm Offset Compensation.
As such programmable current sources were very expensive, (Time Electronics, Keithley) and only decade values were needed, I've designed many budget high precision current sources (< 0.01%), which cost below 50 bucks only.
Frank
PS: Yes, I definitely want to see a teardown of this nice unit, please!