Lightbulb load accuracy

Hello

I was wondering if anyone knew roughly what tolerance on lightbulb wattage was.

I want a simple but accurate test load ideally 1w accurate of 500w, I thought multiple 100w light bulbs but what tolerance would I get?

can anyone recommend an accurate power loading device? as close to 1w accurate 500watts

Reply to
Lander
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The wattage drawn by a bulb is dependant on the voltage. A small change in voltage can have a large change in power (Vsquared over R).

Test loads are available, but they are not cheap. They are commonly used in the revenue metering business to calibrate meters.

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is a good place to start.

Charles Perry P.E.

Reply to
Charles Perry

Thanks, good point, same use I wanted it for, but as you'd have to have that calibrated anyway..., looks like a calibrated clamp meter is the way to go then really, radio spares have some good stuff for UK, Tae.

so that actually would be a way for an energy company to make a bit of extra cash, run your supply at + x% voltage when demand is down and vice versa... hmmm I wonder....

Reply to
Lander

You will have trouble meeting your accuracy requirement. 500 W +/- 1 W means .5% accuracy. That means you will need better accuracy than that for both your voltage and current measurements. Actually your voltage and current measurements will need to be approx. .25% accuracy.

Yes and no. For uncontrolled resistive loads, like a light bulb, a higher voltage means more kWh consumed. For a controlled resistive load, like an oven, a higher voltage means shorter cooking time and roughly the same kWh used, but the demand is higher. Motors using adjustable speed drives are a little trickier but in general you don't get the same benefit as a pure resistor.

Charles Perry P.E.

Reply to
Charles Perry

| Yes and no. For uncontrolled resistive loads, like a light bulb, a higher | voltage means more kWh consumed. For a controlled resistive load, like an | oven, a higher voltage means shorter cooking time and roughly the same kWh | used, but the demand is higher. Motors using adjustable speed drives are a | little trickier but in general you don't get the same benefit as a pure | resistor.

Now calculate the voltage drop on the feed to a mix of those crazy loads :-) Toss in some computer switch power supplies, too.

Reply to
phil-news-nospam

The resistance of a light bulb varies with its filament temperature in a non-linear manner. Light bulbs won't be easy to calibrate.

Reply to
Paul Hovnanian P.E.

Reply to
TimPerry

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