There are three presets marked VR4, VR+ and VR-. Does anyone have an idea what they do?
You guys have been hacking the firmware, so surely three little presets are not such a mystery?
I disagree. These guys are hacking the "settings" of this meter, or the artificial limits. The ones pre-programmed to allow the seller to charge much more for a different model using pretty much the same hardware. I think this is a common theme lately.
The firmware is out of bounds, though interesting hacks are possible beyond what the firmware programmers envisioned as can be seen.
As for the VR's, this is analog stuff - surely you can work this out yourself with a rudimentary "reverse engineering" using a multimeter. Make sure you measure all your VR's and take a photo before twiddling and then mess about to your hearts content - tabulate some data and work out from that how they affect V/R/I.
You will always be able to turn it back to "factory" if you cock up. You could also find something interesting