UPS and ESD monitor puzzle

[openthomas]

So I have a 3m 724 esd workstation monitor. To monitor a antistatic mat the unit requires 2 grounds, one from the socket and another soft ground from say a radiator. You connect the soft ground to the mat, and from another connector on the mat back to the monitor.I connected the 724 monitor through my ups socket and the soft ground to a radiator, but the alarm shows that the mat is not grounded. However when I switch and connect it directly to the socket, the grounds appear equal and the alarm goes out. Why ? Why does the ups not pass ground ?

[SeanB]

It should, but often this fault is not noticed, or the wire is left off to cut cost. You would have to open the UPS and check the wiring to be sure.

[amyk]

It should, but often this fault is not noticed, or the wire is left off to cut cost. You would have to open the UPS and check the wiring to be sure.

A DMM also works for checking ground continuity...

[openthomas]

I just run a continuity check from ground in the wall socket to ground on the UPS socket ? Safe ?

[Monkeh]

I just run a continuity check from ground in the wall socket to ground on the UPS socket ? Safe ?

Why wouldn't it be?