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jshimmin
09-02-2010, 08:55 AM
In checking some test samples, I found some strange numbers -

Input voltage was 13.1 VAC

A 3x2 unit (6 watt) showed a draw of 340 mAmps (4.45 Watts)
Another 3x2 showed 263 mAmps (3.44 Watts)

I tested a 10 and 20 watt Halogen and both were within 10%. I f I dropped the input down to 12 Vac they were both right on.

Is there a different methodology in testing LED's. I do not have a light meter, but should we really need one?

steveparrott
09-02-2010, 10:54 AM
Your findings are consistent with what should be expected. LED's with constant current drivers maintain a constant amperage through the chips.

The current that supplies the driver, however, does not maintain constant amperage over changes in voltage. Lower voltage results in higher amperage(and watts), while higher voltage results in lower amperage (and watts).

I don't think it's very useful to use amp measurements in evaluation of LED's, since most of the factors that degrade LED performance will not affect the current.

A light meter, on the other hand, is extremely important for those who seriously want to monitor lumen degradation.

DMAN
09-02-2010, 09:36 PM
Posted via Mobile Device

David Gretzmier
09-03-2010, 12:23 AM
ah, lumen degradation. I am starting to see hour warranties on LED's using such wording. it was on the back of the new Sylvania's I am testing. 35,000 hours to 70% lumen output. or 30% degradation.