Does a dimmer reduce voltage?

Bobble23 · Mar 27, 2013

Sorry if this is a stupid question but I've just put in a small radial lighting circuit, the last light of which is on a dimmer switch. When I measure the voltage at the light I'm only getting about 150V, even when the switch is turned up full. Is this because the dimmer is taking out some of the voltage or is it more likely I've got a loose connection or something earlier on in the circuit?

Thanks.

micknew · Mar 27, 2013

voltage reduced by dimmer

44ALLAN · Mar 27, 2013

What did you get when you tested between Neutral and earth?

static zap · Mar 27, 2013

Cheap Meter , has it got true RMS?

micknew · Mar 27, 2013

static zap said:
Cheap Meter , has it got true RMS?

Whats that got to do with the question?

static zap · Mar 27, 2013

micknew said:
Whats that got to do with the question?

Re: Meter ,if it was designed for Pure Sine wave,could be confused with chopped up cycles coming out of dimmer !

Is light actually Dim as well, or just reading a worry ?

SYKRAPS · Mar 27, 2013

Ohms law........................

Silly Sausage · Mar 27, 2013

A true RMS meter will calculate V[SUB]rms[/SUB], whereas a cheapo job will just display V[SUB]peak[/SUB]/sqrt(2).

As an electronic dimmer chops off part of the sine wave, a true RMS meter will display less than 230V (in this case).

Badged01 · Mar 28, 2013

Have to agree with Archy there. The dimmer 'chops' off part of the voltage cycle but doesnt actually reduce the voltage. The voltage is aways ~230v so it depends on how your meter 'reads' voltage!.

When you have the dimmer at 'full' I would have thought you should be getting very close to 230v as none of the voltage should be 'chopped'?

stuartcourt · Mar 28, 2013

test voltage at dimmer and then at light if coming in 230 happy days

Bobble23 · Mar 29, 2013

Thanks everyone. I swapped the dimmer for a normal switch and it showed 230V (haven't connected up the actual light yet) so it seems you were all right about my meter getting confused by chopped sine waves. Thanks again.