I have a household, dual module dimmer switch. One module is working and dims a 3A sidelight loop, the downlight loop with 4 drivers doesn't work and I'm fault finding.
I noticed on the working module that the voltage across the terminals is 237V when off and then reduces when on - it's a push on/off and turn dim. The voltage changes when turned as expected.
But I was expecting to see 0V on my tester when off, what am I misunderstanding?
Is the tester and the way the dimmer work showing a potential difference even though no current is flowing?