Photocell and minicell discussion

sotonsteve · **Posted:** Thu Apr 14, 2011 7:25 pm

Phosco152 wrote:

The body, even the slight reduction in diameter at the base, the position of the detector and the window all appear the same. I wonder what the yellow body signifies?

There are some at the car park above the northern portal of the Heathrow Airport Tunnel on Phosco P567s with red bodies.

mazeteam · **Posted:** Fri Apr 15, 2011 12:45 am

Maybe the body colour is for quick identification to a switching setting.... such as Part Night of a 35 Lux ON setting, or something similar...

Phosco152 · **Posted:** Sat Apr 23, 2011 1:20 pm

SELC appear to be colour coding all of their cells. There is a part night version which is black. Of interest it is marked "5 hour part night" with no time reference.

By the markings on the cell, it also appears SELC cells are available with switch points of 8, 10, 14, and 30 Lux as well as the more conventional 70/100 switch points.

mazeteam · **Posted:** Sun Apr 24, 2011 6:11 pm

8 Lux?? In places like Newcastle and parts of Scotland, the cells would never switch on! (Newcastle due to skyglow, Scotland in summer as you can still have light in the sky even at midnight)

Phosco152 · **Posted:** Sun Apr 24, 2011 9:33 pm

Yes, seen it on the base of the cell with my own eyes, I would have thought anything less than 30 Lux must be for specialist applications...

Gramma6 · **Posted:** Sun Apr 24, 2011 11:51 pm

Possibly a silly question, but just exactly how is lux measured?

Stelmer · **Posted:** Mon Apr 25, 2011 12:06 am

Light meter? My dad has one somewhere.

Phosco152 · **Posted:** Mon Apr 25, 2011 6:32 am

Gramma6 wrote:

Possibly a silly question, but just exactly how is lux measured?

With a Lux meter! As Stelmer says, a light meter measures Lux.

Quote:

The lux (symbol: lx) is the SI unit of illuminance and luminous emittance measuring luminous power per area. It is used in photometry as a measure of the intensity, as perceived by the human eye, of light that hits or passes through a surface. It is analogous to the radiometric unit watts per square metre, but with the power at each wavelength weighted according to the luminosity function, a standardized model of human visual brightness perception.

Gramma6 · **Posted:** Mon Apr 25, 2011 10:59 pm

Ok, thanks for the replies!

I googled 'light meter' and it seems to be some sort of hand-held electronic gubbins. Never seen one before! :oops:

mazeteam · **Posted:** Tue Apr 26, 2011 12:43 am

There was one on ebay a few weeks back... but the max it went up to was too low for street lighting, as it was a Menvier unit designed for testing the output from emergency lighting.

I saw some odd photocells today in North Ferriby (east Yorkshire) - they look like a photcell that has been fitted on top of another cell of smaller diameter. no pictures though as I was trying to keep a good average speed on my bike and didn't know how long I had until my train home left Hull!!

Photocell and minicell discussion

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