Thor 10mcp lux at beam center at one meter

[chevrofreak]

I got a Watt Stopper FX-200 Illuminometer the other day. Its only rated to 50,000 lux, but I tested the Thor and it was 120,000+ lux at beam center! /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif /ubbthreads/images/graemlins/ooo.gif

Anyone else get similar readings?

 

[Spacemarine]

I don't have my light meter yet, but as soon as I have it I will also test my thor.

I'm sure you already know that, but I say it anyways. These readings can't be converted into candela, because candela is for point sources of light. You would have to take the reading in at least 100m (around 300 feet) to make the thor appear to be a point source of light. In this distance you could convert your lux readings into candela values.

 

[chevrofreak]

Wasnt trying to convert anything, just wanted to see how much measurable throw it had.

 

[Spacemarine]

I didn't say you were going to. I just posted to make sure noone used your values to convert them into candela to see if the claim of 10 mega candela of the manufacturer was true.

Do you have a possibility to test the thor in a distance of about 10 meters or greater?

 

[chevrofreak]

I do, yes, but my neighbors might think I'm crazy. I'd also need someone brave enough to stand by the meter and read it /ubbthreads/images/graemlins/wink.gif

Maybe Monday.

 

[Spacemarine]

If the USA weren't so far away, I'd come over

 

[Roy]

Here is a quote from a posting I made back on 08-06-04:



"Well...just for grins and giggles, I put my Thor on a 30 Amp regulated power supply at 13.8vdc and tried to fry my light meter!

I set the Thor up on the other side of the room...27 feet from the light sensor (1 11/16 inch in diameter). At the hottest spot in the beam that I could find,I got a reading of 1,182 Fc. Multipling that by the distance to the light squared (27 x 27 = 729) I calculated a value of 861,678 Fc@1Ft!!

My light sensor is MUCH smaller than the size of the light beam generatd by the Thor, so I don't know how valid my 861,678 Fc@1Ft is.... I suspect very low.

As soon as the battery in the Thor gets recharged, I'll do a runtime plot tonight. "

A footnote to the above...at 27 feet I could still feel the heat from the Thor!!!

 

[thesurefire]

/ubbthreads/images/graemlins/happy14.gif Where did you get the power supply you used?

 

[NewBie]

Stock runtime plot, see orange line:

 

[Roy]

thesurefire......

It's an Alinco DM-330MV switching power supply. Ham Radio Outlet or Amateur Electronic Supply should have it.

Here's the spec sheet.

 

[java_man]

[ QUOTE ]
set the Thor up on the other side of the room...27 feet from the light sensor (1 11/16 inch in diameter). At the hottest spot in the beam that I could find,I got a reading of 1,182 Fc. Multipling that by the distance to the light squared (27 x 27 = 729) I calculated a value of 861,678 Fc@1Ft!!


[/ QUOTE ]

Roy,

Because of the size of the source I agree that 861,600 Fc at one foot is not accurate....BUT....I think that number closely represents the peak beam candlepower...if the reading was farther away it would be more accurate, but in either case your measurements are far more accurate than the ridiculously inflated BCP values advertised for the thor /ubbthreads/images/graemlins/au.gif

 

[NewBie]

Seems there might be some confusion here.

Candlepower is not the same as peak beam candlepower.

"Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight. Is it a measure of how much light falls upon an object some distance away? No. That's illuminance. Is it a measure of how well we see an object that is illuminated by that light source? No. That's something all together different, and we are not going there!

Nowadays we use the term CANDELA instead of candlepower. Candlepower, or CANDELA is a measure of how much light the bulb produces, measured at the bulb, rather than how much falls upon the thing you want to light up. Further confusing the matter is beam focus. That's how much candlepower can be focused using a reflector/lens assembly. Obviously, if you project all your light bulbs intensity at a given spot, or towards something, it will be more intense, and the illuminance will be higher.

And here comes the confuser! A candlepower as a unit of measure is not the same as a foot-candle. A candlepower is a measurement of the light at the source, not at the object you light up."
http://www.theledlight.com/lumens.html

So to measure candlepower, a person has to gather up all the light emitted from a source.

A simple Lux meter or foot-Candle meter doesn't do that.

 

[Spacemarine]

[ QUOTE ]
Roy said:
My light sensor is MUCH smaller than the size of the light beam generatd by the Thor, so I don't know how valid my 861,678 Fc@1Ft is.... I suspect very low.

[/ QUOTE ]

Since you aren't mesuring lumens, the size of your sensor should be totally irrelevant.

 

[Spacemarine]

I'm sorry NewBie, but I think you got it all wrong...


[ QUOTE ]
NewBie said:
"Candlepower is a way of measuring how much light is produced by a light bulb, LED or by striking an arc in a Carbon-Arc spotlight.

[/ QUOTE ]

That's wrong. What you mean is Lumen. Candela is a measure of the light emitted in a particular direction.

[ QUOTE ]
NewBie said:
So to measure candlepower, a person has to gather up all the light emitted from a source.

A simple Lux meter or foot-Candle meter doesn't do that.

[/ QUOTE ]

No. To measure candlepower a person has to measure how much light the source emits in a given direction. He or she normally does that by measuring how much light falls from the source onto a surface in a known distance and convert these readings into Candela.

Therefore a simple Lux meter is enough.

 

[java_man]

No confusion ...

Roy measured the FootCandles, the light intesity, at his sensor...in this case 27 feet from the reflector.

Beam Candlepower equals the candlepower of a bare source that would produce the same illumination at the respective point if located the same distance away.

for a point source, that is simply the distance in feet squared times the foot-candles measured.

for non-point sources, the greater the distance between the sensor and the source, the smaller the error due to the source size.

 

[Dolby]

Ya' know I am completely confused. I'm a chemist in real life so you would think some of this technical stuff would get absorbed! /ubbthreads/images/graemlins/confused.gif

 

[Spacemarine]

Here's some good information about all this stuff:
http://en.wikipedia.org/wiki/Lux

Just click you through all the other terms like lumen, candela etc...

 

[NewBie]

[ QUOTE ]
Spacemarine said:
I'm sorry NewBie, but I think you got it all wrong...



[/ QUOTE ]


LOL.

Lumen (unit of luminous flux). The lumen is an SI derived unit for luminous flux. The abbreviation is lm and the symbol is F Fv. The lumen is derived from the candela and is the luminous flux emitted into unit solid angle (1 sr) by an isotropic point source having a luminous intensity of 1 candela.

See this for a definition of candlepower:
"CANDLEPOWER: A measure of luminous intensity of a light source in a specific direction, measured in candelas (see above)."
http://www.mts.net/~william5/library/epalight.htm

For more common sense, see the bottom of this:
http://www.edn.com/article/CA484530.html

The candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540´ ´10 12 hertz and that has a radiant intensity in that direction of 1/683 watt per steradian.
The candela is abbreviated as cd and its symbol is Iv. The above definition was adopted by the 16th CGPM in 1979.
The candela was formerly defined as the luminous intensity, in the perpendicular direction, of a surface of 1/600 000 square metre of a black body at the temperature of freezing platinum under a pressure of 101 325 newtons per square metre. This earlier definition was initially adopted in 1946 and later modified by the 13th CGPM (1967). It was abrogated in 1979 and replaced by the current definition.

 

[Spacemarine]

[ QUOTE ]
NewBie said:
LOL.

[/ QUOTE ]

I don't know if that means that you agree or disagree with me that your statements were wrong.

The rest of your new post of totally correct, although I doubt that a lot of people undestand the scientific definition of candela

 

[Roy]

Is the following a true statement?

1 Fc@1Ft = 1 LUX@1M = 1 Cd