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®

Instruction Sheet

012-11060A

Light Level Sensor

PS-2177

*012-11060*

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*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 mea-

sure 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, mea-
sured 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.

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*

Eight pin mini- 

DIN connector

Light Dome

Light Level 

Sensor

Range Select 

Buttons

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