INDUSTRIAL ENGG - LAB
. EXPERIMENT-3 .
To determine the light level in different workplaces of an industry. .
Date:22/09/2020 Name : Arvind
Lakra(20186022_PIE)
Introduction:-
The majority of industrial tasks depend for their efficiency on adequate vision; therefore lighting plays an important
part in determining the efficiency with which tasks are carried out .The amount of light required for the performance
of a visual task is influenced by four factors which are independent.These are:
● The size of the object
● The contrast between the object and its immediate surround
● The reflectivity of the immediate surround
● Time allowed for seeing.
The amount of which is required for the task cannot be determined until all these factors have been established.
Objective:-
In this experiment ,students have to determine the illumination level of a number of workstations.They are required
to critically analyze the findings and comment for improvements.
Terms and definition:-
Lumen is a unit of light flow or luminous flux. The lumen
rating of a lamp is a measure of the total light output of the
lamp. The most common measurement of light output (or
luminous flux) is the lumen. Light sources are labeled with
an output rating in lumens.
Lux is the metric unit of measure for illuminance of a sur-
face. One lux is equal to one lumen per square meter.
Average maintained illuminance is the average of lux levels measured at various points in a
defined area.
Color Rendering Index (CRI) is a measure of the effect of light on the perceived color of objects.
To determine the CRI of a lamp, the color appearances of a set of standard color chips are measured
with special equipment under a reference light source with the same correlated color temperature as
the lamp being evaluated. If the lamp renders the color of the chips identical to the reference light
source, its CRI is 100. If the color rendering differs from the reference light source, the CRI is less
than 100. A low CRI indicates that some colors may appear unnatural when illuminated by the lamp.
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Preparation (before Measurements):-
Before starting the measurements, the following care should be taken:
• All lamps should be operating and no luminaires should be dirty or stained.
• There should be no significant obstructions to the flow of light throughout the interior,
especially at the measuring points.
• Accuracies of readings should be ensured by
– Using accurate illuminance meters for measurements
– Sufficient number and arrangement of measurement points within the interior
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– Proper positioning of illuminance meter
– Ensuring that no obstructions /reflections from surfaces affect measurement.
• Other precautions
– If the illuminance meter is relatively old and has not been checked recently, it
should be compared with one that has been checked over a range of illuminances,
e.g. 100 to 600 lux, to establish if a correction factor should be applied.
– that the number and arrangement of measurement points are sufficient and
suitable to obtain a reasonably accurate assessment of the average illuminance
throughout an interior. The procedure recommended in the CIBSE Code for
such site measurements is as follows:
The interior is divided into a number of equal areas, which should be as square as possible.
The illuminance at the centre of each area is measured and the mean value calculated. This
gives an estimate of the average illuminance on the horizontal working plane.
Theory:-Light Level or Illuminance is the total luminous flux incident on a surface per unit area. The area - the
work plane - is where the most important tasks in the room or space are performed.
Illuminance can be expressed as
E=Φ/A
where
E = light intensity, illuminance (lm/m2, lux)
Φ = luminous flux - the quantity of light emitted by a light source (lumen, lm)
A = area (m2)
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There are several types of lighting metrics and measurements used in the lighting industry. So far, we’ve covered
measurements related to light intensity – lumens, footcandles and lux.
While these are useful to lighting experts, how do these terms relate to the real world? We need a little context. A
typical classroom, for example, is recommended to have a light level of around 30-50 footcandles or 300-500 lux.
Compare this to a professional laboratory which the lighting standards recommend have a light level of 75-120 foot
candles or 750-1200 lux. The differences in recommended light levels are published by the IESNA (Illuminating
Engineers Society of North America). The recommendations are based on years of visual testing to determine how
much light the human eye needs to properly see different tasks with varying levels of detail. You can see from this
example how specific environments have very different light level requirements.
To further explain this, you might be thinking about the biggest natural light source we have – the sun. Examples of
common light levels:
● Bright Summer Day: 100,000 Lux (~10,000 footcandles)
● Full Daylight: 10,000 Lux (~1,000 footcandles)
● Overcast Day: 1,000 Lux (~100 footcandles)
● Traditional Office Lighting: 300-500 Lux (30-50 footcandles)
● Common Stairway: 50-100 Lux (5-10 footcandles)
● Twilight: 10 Lux (1 footcandle)
● Full Moon: <1 Lux (<0.1 footcandle)
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Simple rules for lighting
1. Make full use of daylight in the factory. 2. Choose appropriate visual backgrounds for walls, ceilings, etc.
3. Find the best place for the light source to avoid glare, etc. 4. Use the most appropriate lighting devices and
fixtures. 5. Avoid shadows. 6. Ensure regular cleaning and maintenance of lights and windows.
Procedure:-
1. Switch on the lux meter.
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2. Ensure initial reading should be “Zero”,otherwise adjust the zero by using “zero offset”.
3. Range A. measures 0 to 1999 LUX resolution 1.
Range B. measures 2000 to 19990 LUX resolution 10.
Range C measures 20000 to 500000 LUX resolution 100.
4. Slide the switch as per the requirement(A or B or C).
5. Hold the light sensor facing towards the light.
6. The display will show Lux value.
7. The multiplication of displayed value with multiplying factor will be the actual lux.
8. Monitoring of lux level.
9. Hold the lux meter at a minimum five location.
10. Measure the lux at 1meter height from ground level.
11. Record the reading in lux level monitoring record.
12. The average lux of all readings will be lux level in the room.
Acceptance criteria:-
The lux level measured shall not be less than ,400 lux for production areas,300 lux for sampling and dispensing
booths
Calculations:-Illumination can be calculated as
E = Φl Cu LLF / Al
where
E = illumination (lux, lumen/m2)
Φl = luminance per lamp (lumen)
Cu = coefficient of utilization
LLF = light loss factor
Al = area per lamp (m2)
Example - Illumination
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10 incandescent lamps of 500 W (10600 lumens per lamp) are used in an area of 50 m2. With Cu = 0.6 and LLF = 0.8
illumination can be calculated as
E = 10 (10600 lumens) (0.6) (0.8) / (50 m2)
= 1018 lux
Luminance
Luminance is the only basic lighting parameter that is perceived by the eye. It describes on the one hand a light
source’s impression of brightness, and on the other, a surface and therefore depends to a large extent on the degree
of reflection (color and surface).
Result:-As I haven't performed the experiment practically in the lab but I have studied the related
articles and I understood now the importance of light level at different workplaces of an industry.
Areas for Improvement:-
• Look for natural lighting opportunities through windows and other openings
• In the case of industrial lighting, explore the scope for introducing translucent sheets
• Assess scope for more energy efficient lamps and luminaries
• Assess the scope for rearrangement of lighting fixtures
Conclusion:-
There are many terms and technologies used when it comes to the power of light and light measurement. It is key to
understand how all of these unique aspects come together.
Understanding the measurement of light helps us, as a lighting solutions provider, meet the brightness and uniformity
requirements of your specific applications.
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