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(42S) Room Cavity Ratio, Luminous Intensity and Illuminance - Eddie W. Shore - 05-13-2019 01:28 PM
Blog entry: http://edspi31415.blogspot.com/2019/05/hp-42sdm42free42-room-cavity-ratio.html
Room Cavity Ratio
The room cavity ratio is used to assist in calculating lighting efficiency in determining where to place ceiling lights in an office room. The formula is:
RCR = INT( ( 5 * H * ( L + W ) ) / ( L * W ) )
where:
L = length of the room
H = height difference between floor cavity and ceiling cavity
W = width of the room
HP 42S/DM42/Free42: Solver RCR
Code:
LBL "RCR"
MVAR "H"
MVAR "L"
MVAR "W"
MVAR "RCR"
5
RCL * "H"
RCL "L"
RCL + "W"
*
RCL "L"
RCL * "W"
÷
IP
RCL - "RCR"
ENDExample 1:
Input: H = 5.5, L = 16.8, W = 13.7. Result: RCR = 3
Example 2:
Input: H = 5.5, L = 16.8, RCR = 4. Result: H = 7.1650
Sources:
Dilouie, Craig. "Lighting Design: Example of Role Surfaces Play in Lighting Efficiency" LightNOW https://www.lightnowblog.com/2010/06/example-of-role-surfaces-play-in-lighting-efficiency/ June 16, 2010. Retrieved March 31, 2019
"Room Cavity Ratio, RCR" Illuminating Engineering Society. https://www.ies.org/definitions/room-cavity-ratio-rcr/ July 5, 2018. Retrieved April 28, 2019
Luminous Intensity and Illuminance
The follow equation relates the luminous intensity (measured in candelas, cd) and illuminance (measured in lux) of a light source. The equation assumes the light source radiates a spherical matter.
E = I / R^2
E = illuminance
I = luminous intensity
R = radius of the sphere's light (meters)
HP 42S/DM42/Free42: Solver ILSPH
Code:
LBL "ILSPH"
MVAR "E"
MVAR "I"
MVAR "R"
RCL "E"
RCL "I"
RCL "R"
x ↑ 2
÷
-
ENDExample:
Example 1:
Input: I = 10 cd, R = 2 m. Result: 2.5 lux
Example 2:
Input: R = 3.65 m, E = 30 lux. Result: I = 399.6750 cd
Sources:
Daryanani, Sital "Building Systems Design With Programmable Calculators" Architectural Record Books. McGraw-Hill Book Company: New York. 1980. ISBN 0-07-015415-5
Zumtobel "The Lighting Handbook" Zumtobel Lighting GmbH. Dornbirn, Austria. 6th Edition: 2018 https://www.zumtobel.com/PDB/Ressource/teaser/en/Lichthandbuch.pdf
RE: (42S) Room Cavity Ratio, Luminous Intensity and Illuminance - Luigi Vampa - 05-14-2019 08:15 AM
I wasn't aware of the RCR. Thanks for sharing, Eddie.
RE: (42S) Room Cavity Ratio, Luminous Intensity and Illuminance - SlideRule - 05-14-2019 02:46 PM
This illustration
[attachment=7250]
may be helpful.
as well as Ligthing Design Calculations (20 pages): tables, illustrations, worksheets, charts etc.
BEST!
SlideRule
RE: (42S) Room Cavity Ratio, Luminous Intensity and Illuminance - Eddie W. Shore - 05-15-2019 02:04 AM
Thank you everyone!
Eddie