My module has got the wires as on the picture (4digits 30V/3A, red/blue led display).
The black wires are common afaik.
Therefore my question on how you would wire it when you are using shunt in the gnd path.
PS: I've glanced at my PSU module and the refresh rate is something like 3-4x per second at least..
PPS: I put a 7805 (with a small heatsink attached) in front of the meter's Vcc, still working
(the PSU is single voltage, 28V at filter).