Longer Lamp Life

QST February 1999 pg: 64

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Almost 20 yrs ago when I was working as an Electro-Optics Physicist I used to design devices with miniature halogen lamps. There was a family of equations that would give the life of a lamp dependent on its rated and operational voltages. I could not find the book these equations were in, so I looked up Welch Allyn and found the following:

Welch Allyn = http://hi-lux.com/minihalogen/tec.html

The information we want is locaed on the miniature halogen lamps Electrical Characteristics page, so select: Electrical Characteristics which is should be: ISL297A.pdf

Va = Applied Voltage Vd = Design Voltage

Rerated Life = [Vd/Va]exp12.0 x Life at Design Voltage ***

Rerated Current = [Va/Vd]exp0.55 x Current at Design Voltage

Rerated Candlepower = [Va/Vd]exp3.5 x Candlepower at Design Voltage

Now your readers, who might be interested, will know how long (in general) that de-rated lamp will last.

72 & 73 de KE3FL Phil K Consulting Engineering Physicist

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