Lights and Illumination

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To do any kind of comparison between light sources for running solar devices, we need an idea about how bright different places are. We need to then be able to compare environmental light intensity wit different light sources we can use on our workbench.

Light intensity measurements made with with a Sekonik Studio Deruxe II meter. Outdoor measurements made noon, February 19, 2010 at Chicago, IL, 41.88 deg North.

To do any kind of comparison between light sources for running solar devices, we need an idea about how bright different places are. We need to then be able to compare environmental light intensity wit different light sources we can use on our workbench.

Light intensity measurements made with with a Sekonik Studio Deruxe II meter. Outdoor measurements made noon, February 19, 2010 at Chicago, IL, 41.88 deg North.

Location

Meter w/ flat lens -w/o slide (max. value this range = 1250)

(foot-candles)

Meter w/ flat lens – w/ 32x attenuating slide -

raw meter readings

Usable Diameter

Notes

Classroom #1 floor

10-15

Underrange

 

 

Classroom #1 table

17

 

 

 

Classroom #2 table

20

 

 

 

Hallway

0-20

 

 

 

Worktable under 4ft 30W florescent wall sconce – white paint on wall

80

 

 

 

Sunny day - North Window (indoors)

240 facing up

320 facing sky

7

 

 

17-story Building shade – vertical sky view (outdoors)

480

15

 

 

17-story Building shade – facing the building (outdoors)

320

10

 

 

[missing : cloudy sky]

 

 

 

 

Direct sun

Overrange

(10,240 calc.)

320

 

 

“normal” value for direct sun (according to the Internet)

10,000 ft-candles

 

 

 


 

For doing actual tests, we'll need some reference measurements on a few light sources to run our experiments.



Philips Metal-Halide 70W Cool White PAR-38 Flood

Distance (cm)

Meter w/ flat lens

foot-candles

(calculated)

Meter w/ flat lens – w/ 32x attenuating slide -

raw meter readings

Usable Diameter of beam

(cm)

Notes

200

160

-

100

 

150

320

-

50

 

100

(800)

25

 

 

50

(3,200)

100

 

 

25

(9,600)

300

 

 

22

(10,240)

320

10

“Direct sun” equiv.

20

(12,800)

400

 

Hot.

15

(16,000)

500

 

Meter seemed unhappy? Hot.

10

(19,200)

600

 

Hot.


 



Arm-type desk Lamp from Lowe's. Pseudo-halogen bulb – 40W 120V – 5cm parabolic reflector lamp-head

 

Distance (cm)

 

Meter w/ flat lens

foot-candles

 

Meter w/ flat lens – w/ 32x attenuating slide -

raw meter readings

Usable Diameter of beam

(cm)

Notes

65

12

-

200

 

60

20

-

 

 

20

120

-

 

hot

15

150

-

 

 

10

340

-

20

 


 

This lamp is best for bench work. It has its own page



Philips Metal-Halide MH175/RFL PAR-38 Flood 55 deg. Beam - 3700K – 10,000 initial lumens

Distance (cm)

Meter w/ flat lens

foot-candles

(calculated)

Meter w/ flat lens – w/ 32x attenuating slide -

raw meter readings

Usable Diameter of beam

(cm)

Notes

150

(1,250)

40

20

 

100

(2,560)

80

 

 

48

(10,240)

320