Hello,

I am wiring a wls-pva200 ammeter for a 120 – 140 volt dc system.  However, the voltage is not detected when using an external power supply. it always shows up as th epower supply voltage.

There are only 3 wires.  red/black/yellow.
yellow goes to the source positive (+) 120 volts.
red to my 12 volt positive (+) (power supply)
black to my 12 volt negative (-) (power supply)

The wiring diagram for external power supply makes no sense whatsoever.
I cannot splice the black to both the 12 volt power supply negative (-) and the 120 volt source negative (-) without causing serious problems.

How in the world am I supposed to give the source negative (120 volts DC) access to the DROK wls-pva200 so it can read the source voltage?

Thanks much in advance.
-Timothy