Causes of high-voltage neutral-ground?

[nunodonato]

Just finished setting up my first ground rod, and decided to test the voltage difference between the ground and the output of my inverter. I'm getting super odd values and have no idea what could be causing this (note: there are no connections anywhere, yet, I'm measuring straight in the inverter AC output and the ground wire that goes to the rod, so its not a case of wires touching or bad insulation...): Live-Neutral: 230V
Live-Ground: ~110V
Ground-Neutral: ~100V
My inverter has no instructions regarding grounding (not sure if I should bond earth-neutral!)...
Is this the inverter acting up or could be some other issues?

I'm using 6mm

[Mike90250]

Try connecting a standard light bulb in a socket, and use it as a volt meter. Sometimes stray static voltage exists and a 100Mohm/volt meter will read wacky numbers. But a 10 watt 230V bulb will not respond to stray voltage. if it lights, you have a problem. Why does a 230V system have a neutral ? I thought only split phase USA 240V/120V used neutral.