1.0 Title of Experiment
Experiment 1: Measurement of Illuminance
2.0 Objective of the Experiment
Learning Outcome: To determine the luminous intensity of (2x36W) batten type light fittings.
3.0 Equipment
1. Luminous meter
2. (2x36W) batten type light fittings
3. Laser distance measure.
Figure 4.1: Luminous meter & laser distance measure
Reference Standard:
IES Lighting Handbook (1968)
Light 1
Ceiling
Y
Lux Meter
Given the Illuminance Formula (or Cosine Law of Illuminance) is:
E=
𝐼
× 𝑐𝑜𝑠𝜃
𝑑2
Where,
E= Illuminance (or density of luminous flux) reaching a surface (lm/m² or lux)
Light 2
I= Luminous intensity or strength of a light source (candle power or candela, cd)
D= Distance between light source and surface (m)
Find the luminous intensity of the lights.
Conversion:
1 candela = 12.57 lumen
1cd/m² = 12.57 lm/m² (lux)
4.0 Precaution
1. Care must be taken to ensure that light incident on the sensor is not obstructed by the
operator or any objects that are not part of the measurement such as shields for
reflections.
2. Check the zero setting on the scale when the sensor is fully covered.
3. Check the condition of the battery in the instrument.
4. The artificial light source (fluorescent lamps) should be switched on for about 15
minutes before the measurements are taken in order to allow for the lamps to be
completely warmed up. If the luminary (light fitting) is of the fully enclosed type, a
longer stabilization time is needed.
Note: E (artificial light) = E (Lights ON) – E (Lights OFF
5.0 Experiment Procedures
1. Luminous meter was placed in the middle path between 2 light fittings as shown in
Figure 1. (b must be equal distance)
2. Distance a is measured vertically downwards to working plane where the lights
measurement is taken.
3. d is calculated using Pythagoras Theorem.
4. The illuminance (lux) from the luminous meter is calculated. Substitute into the
equation given and solve to determine the luminous intensity.
5. The experiments are repeated at various spots n different rooms in the building
laboratory with the lights on and off.)
6.0 Experimental results
Location
a (m)
b (m)
d (m)
Theta,
Horizontal 2.967
on floor
1.805
3.47
31.31°
Horizontal 2.36
on chair
1.805
2.97
37.41°
Vertical
on floor
2.967
1.092
3.16
20.21°
Vertical
on chair
2.36
1.092
2.60
24.83°
7.0 Discussions
Horizontal on floor
E (artificial light) = 52.3 (Lights ON) – 21 (Lights OFF)
= 31.3 lx
𝐼
E = 𝑑2 ×𝑐𝑜𝑠𝜃
31.3 =
𝐼
3.472
×cos 31.31 °
I = 441.12 cd
Horizontal on chair
E (artificial light) = 48.3 (Lights ON) – 15.3 (Lights OFF)
= 33 lx
𝐼
E = 𝑑2 ×𝑐𝑜𝑠𝜃
33 =
𝐼
2.972
×cos 37.41 °
I =366.47 cd
Vertical on floor
E (artificial light) = 45.1 (Lights ON) – 7.8 (Lights OFF)
=37.3 lx
𝐼
E = 𝑑2 ×𝑐𝑜𝑠𝜃
37.3 =
𝐼
3.162
×cos 20.21 °
I = 396.90 cd
Vertical on chair
E (artificial light) = 39.8 (Lights ON) – 7.9 (Lights OFF)
= 31.9 lx
𝐼
E = 𝑑2 ×𝑐𝑜𝑠𝜃
31.9 =
𝐼
2.602
×cos 24.83 °
I = 237.61 cd
Hew Kian Lock (17WVD03975)
Individual Introduction
Good lighting plays an important role in safeguarding health at work by enabling
employees to perform their work comfortably and efficiently. It also allows employees to
read clearly labels and safety instructions (such as those affixed to chemical containers) to
ensure compliance with safety measures for the prevention of hazards. Accordingly, there
should be an appropriate level of the light falling on the surface on which employees are
working. Excessive contrast, strong glare and light flickering in their fields of vision are also
inappropriate.
Measurement of illuminance is a common parameter in a lighting assessment. In order
to perform this measurement, light is measured by using a lux meter which is used to measure
the intensity of light falling on a surface.
In photometry, luminous intensity is a measure of the wavelength-weighted power
emitted by a light source in a particular direction per unit solid angle, based on the luminosity
function, a standardized model of the sensitivity of the human eye. intensity is the candela
(cd), an SI base unit.
Individual Discussion
1. Explain the following terms:
a) Light – Light is energy in form of electromagnetic radiation.
b) Luminous intensity – Luminous intensity (I) is the power of a light source or
illuminated surface to emit light in a particular direction.
c) Luminous flux – Luminous flux (F) is the rate of flow of light energy.
d) Illuminance – Illuminance (E) is the density of luminous flux reaching a surface.
3. Compare the results of illuminance, E (lux) obtained from your experiments in the
various rooms with values obtained from standard lighting requirements. What are some
typical values of service illuminance for (a) street lighting (b) hallway (c) home (d) classroom
(e) office (f) shop display? Comment on your findings.
a)
b)
c)
d)
e)
f)
Street Lighting – 100~200 lx
Hallway – 100~200 lx
Home – 150~300 lx
Classroom – 300~500 lx
Office – 300~750 lx
Shop Display – 300~750 lx
Generally, factors that affect the effectiveness of illumination are quantity and quality of
light, amount of flicker, amount of glare, contrast and shadows. Each factor must be
adjusted differently to optimize illumination in emergency, safety, operations, and
security situations, for instance. Lighting Standards also serve to address the plethora of
other concerns associated with the design, placement, installation, and minimum energy
requirements and efficient allocation of illumination in different locations with different
purposes, as well as the efficiency, durability, cost, and maintainability
4. Discuss some considerations affecting lighting design in buildings.








Light quantity: Depends on the nature of the task & the light output of lamp &
luminaire.
Natural light : May be used as a complete source of light or to supplement
artificial light sources.
Colour quality: Depends on the requirements of the task & the colour rendering
properties of the source.
Glare: Depends upon the brightness & contrast of light sources & surfaces, & the
viewing angles.
Directional quality: Depends on the three-dimensional effect required & the
nature of the lamp & luminaire.
Energy use: Depends on the electrical efficiency of the lamps & the use of
switches.
Costs: Depend on the initial cost of the fitting; the cost of replacing the lamp
( including labour); & the electricity consumption of the lamps.
Physical properties: Include size, appearance & durability of fittings.
Individual Conclusion
The number of lamp in a classroom, office or other place is very important for the
person who stay there or doing the work at there. It is because if too many lamp in that place,
the luminous intensity at there will high this will cause the person working at there felling
unsatisfactory and inappropriate. If too less lamp also will cause the worker unsatisfactory
and inappropriate. So the lighting standards are important to design the light in that place cant
too high and cant too low must appropriate.
In conclusion, this experiment has improve my knowledge about Illuminance. Thus,
good lighting plays an important role in safeguarding health by enabling people to perform
their work in good efficiency.
References
Labour Department, A Simple Guide to Health Risk Assessment - Office Environment Series
- Lighting in Offices, Viewed 27 Nov 2017
Mcmullan, R., (2007). Environmental Science in Building. 6th Edition. New York: Palgrave
Macmillan , Viewed 27 Nov 2017
Smith B.J,, Phillips G.M. and Sweeney M.,(1982). Environmental Science. New York:
Longman, Viewed 27 Nov 2017
Wikipedia 2017, Luminous intensity, Viewed 27 Nov 2017
<https://en.wikipedia.org/wiki/Luminous_intensity>
n.d., Illuminance - Recommended Light Level, Viewed 27 Nov 2017
<http://www.engineeringtoolbox.com/light-level-rooms-d_708.html>