PASCO PS-2177 User Manual
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Light Level Sensor
Eight pin miniDIN connector
Light Dome
Light Level
Sensor
Range Select
Buttons
PS-2177
Instruction Sheet
012-11060A
*012-11060*
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Included Equipment Part Number
Light Level Sensor PS-2177
Recommended Items
PASPORT Extension Cable PS-2500
PASCO Interface Catalog or web site*
Data Acquisition Software Catalog or web site*
*See the PASCO catalog or web site at www.pasco.com for compatible PASPORT interfaces and Data Acquisition Software..
Introduction
Photometry deals with the measurement of visible light as perceived by human eyes. The PASPORT Light Level
Sensor measures illuminance in lux. The readings of the sensor mimic the wavelength sensitivity of the human
eye, which is most sensitive in the green part of the spectrum (peaking at about 555 nanometers). This is
achieved with a green filter in the sensor.
In photometry, illuminance is the luminous flux incident on a surface, per unit area. In other words, it is the measure of the intensity of the incident light, wavelength-weighted to correlate with human brightness perception.
Illuminance is measured in lux, or lumens per square meter. Luminous flux, measured in lumens, is the perceived
power (energy per unit of time) of light. One lumen is defined as the luminous flux of light produced by a light
source that emits one candela of luminous intensity over a solid angle of one steradian. Luminous intensity, measured in candela, is the wavelength-weighted power emitted in a particular direction per unit solid angle. If a
light source emits one candela, a metric (SI) base unit, it emits monochromatic green light with a frequency of
540 terahertz (THz) that has a radiant energy of 1/683 watts per steradian in a given direction. A one-hundred
watt incandescent light bulb emits about 120 candela. A uniform one candela source emits 12.6 lumens.
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Model No.PS-2177 Introduction
PS-2500 PASPORT
Extension Cable
About the Sensor
The PS-2177 Light Level Sensor uses a silicon photodiode that produces a voltage
that is proportional to light intensity. The photodiode has a spectral response range
from 320 to 730 nanometers (nm) and a peak sensitivity at 560 nm, which is very
close to the peak sensitivity wavelength of the human eye. The maximum dark current is 10 picoamperes at one volt. The accuracy is ±10%.
Light Level Ranges
The sensor has three ranges which can be selected using the range select buttons on
the sensor. The range for each button is represented by an icon.
Icon Light Level Resolution
Candle 0 to 1,500 lux 0.5 lux
Light bulb 0 to 15,000 lux 5 lux
Sun 0 to 150,000 lux 50 lux
Illuminance: Typical Readings
The following table shows typical readings for a variety of conditions
Condition Illuminance (lx) Condition Illuminance (lx)
Sunlight 100,000 Quarter moon 0.01
Full daylight 10,000 Starlight 0.001
Overcast day 1,000 Warehouse 150
Very dark day 100 Offices, labs 500
Twilight 10 Supermarkets 750
Deep twilight 1 Operating rooms 1,000
Full moon 0.1 Detailed drawing work 1,500 to 2,000
Usage
The sensor can be used for a variety of experiments.
• Plant growth versus light intensity.
• Light intensity through polarized filters.
• Amounts of solar energy in various locations.
• Relationship of light intensity versus distance for a point source.
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