how to measure wattage?

[Brian Gaff]

Are these bulbs working on AC or DC? Brian

[Brian Gaff]

Besides, if the bulbs will be getting hotter if they are higher wattage then so will the transformer, and the fittings so it might not be safe to exceed what is there to start with. Of course you could redesign the innards to use leds or something.

Brian

[Dave Plowman (News)]

At very low resistance - 0.something of an ohm?

[Dave Liquorice]

What switch over? The switch is a dead short across the meter. As near as damn it all the on surge current will pass through the switch. You then open this switch making all the steady state current flow through the meter. Think of the switch as a socking great big shunt.

[meow2222]

The easiest way is to resistance test new and old lamps and compare. If you want more info, cold resistance is somewhere in the region of a tenth hot resistance.

NT

[Dave Liquorice]

You don't need to measure the actual wattage, just the relative wattage. The cold resistance will do for this, if the new and old are more or less the same (within a few ohms) then they are the same wattage.

Just measured a selection of 60 W GLS bulbs they are about 60 Ohms cold, various forms of 40 W ordinary tugnsten filament bulbs have a cold resistance of around 110 Ohms. Don't have any halogen bulbs to measure but I seen no reason why the basic principle of the above should change.

[F Murtz]

Look at the transformer wattage or current and use the same or similar total for the lamps. don't use lesser rated lamps than the transformer rating if it has a copper transformer as the voltage goes up and lamp life reduces.

[meow2222]

A huge 16:1 resistance ratio.

NT

[Dave Plowman (News)]

A 20 watt 12 volt halogen is something like 0.5 ohm cold. ;-)

[Ian Jackson]

In message , "Dave Plowman (News)" writes

I'll check next time I come across my cheap meter.

[Dave Liquorice]

And a 50 W one is? 0.2 ohm. My cheapo "sold as faulty" meter can measure well enough for that. One does have to make sure you have good connections between probes and object though.

[ss]

Thanks I will check them out tomorrow.