Lamp anomaly

Hi,

I tested a 75W Osram clear lamp & a 70W No Frills halogen (claims

100W equivalent) - the Osram measured 54ohms and the halogen 56ohms.

On 240V, the Osram drew 325mA and the halogen 302mA.

The resistance rises are 13.7 times and 14.2 times = essentially the same filament temps.

However, the filament in the Osram is longer by about 40% plus the wire is also slightly thicker.

Now, light output is proportional to surface area for equal temps, so the Osram MUST deliver more light.

Putting each lamp inside a white, 15cm spherical ceiling fitting and using a DSE lux meter - I found the Osram put out fairly even light in all directions while the halogen is uneven and quite poor in the downward direction.

Dunno which is brighter overall - SFA in it really.

Except one is banned and the other is legal ......

... Phil

Reply to
Phil Allison
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Pretty interesting, Phil. Is it possible that different filament composition could mean that the filaments are not actually at similar temps though?

They're double coils aren't they (a coiled coil)? Can you actually see this? My eyes aren't good enough to pick it, but with enough magnification it's visible.

Is all the emission from the metal surface, or does some come from a partial plasma around the surface? Because the extent of that plasma would change the effective surface area.

Hmm, right where you're most likely to want light. That's pretty crap.

Clifford Heath.

Reply to
Clifford Heath

**Another good reason why I always avoid dodgy lamps and stick to decent manufacturers. The worst I've seen are those Mirabella crap.

On a related matter, I recently purchased an Ecogem S9041 WW (Warm White) 11 Watt LED downlight. Not only does it deliver respectable light output (680 Lumen), but the spread of light is similarly impressive (it is fitted with a nice diffuser). It is supplied with an electronic 'transformer' that is suitable for use with dimmers.

Anyway, a friend is fitting her new home with LED downlights and I suggested she examine the Ecogem. Naturally, she reacted with horror at the price $46.00 wholesale) and elected to use some $20.00 ones she found. Sadly, she finds that she needs more than twice as many to do the same job as the Ecogems. More holes, more electricians' time......... Reliability is unknown.

A fool and her money............

--
Trevor Wilson www.rageaudio.com.au
Reply to
Trevor Wilson

** The colour of the two lamps looks very close, the halogen is a tad whiter.
** Nope - simple coils that look identical.
** The gas ( ie nitrogen or iodine) would be convecting rapidly near the filament and AFAIK does not ionise.

A longer coil at the same temp must deliver more light.

.... Phil

Reply to
Phil Allison

I've had those incandescents literally explode off the ceiling and shatter on the floor!

--
rgds, 

Pete 
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Reply to
felix_unger

"felix_unger"

** Errr - like this:

formatting link

See half way down the page.

BTW:

The other two CFLs were ready to go the exact same way.

Woolworths " ESSENTIALS " brand 20 watt and 22 watt.

.... Phil

Reply to
Phil Allison

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