Physics Lab Equipment

LEOI-37 Measurement of Photoelectric Characteristics of Photosensitive Sensors

LEOI-37 Measurement of Photoelectric Characteristics of Photosensitive Sensors


Photosensitive sensors are sensors that convert light signals into electrical signals, also known as photoelectric sensors. They can be used to detect non-electric quantities that directly cause changes in light energy, such as light intensity, light illuminance, radiation temperature, and gas composition analysis, etc. They can also be used to detect other non-electric quantities that can be converted into changes in light energy, such as part size, surface roughness, displacement, speed, acceleration, object shape, working state recognition, etc. Photosensitive sensors have features of non-contact, fast response and reliable performance. 

The physical basis of photosensitive sensors is the photoelectric effect, in which many electrical properties of semiconductor materials are changeable upon light exposure. The photoelectric effect is usually divided into external and internal two categories. The external photoelectric effect refers to the phenomenon of electrons escaping from the surface of the object under light exposure, also known as the photoelectric emission effect. This kind of photoelectric device based on external effect includes photoelectric tube, photoelectric multiplier tube, etc. 

The internal photoelectric effect refers to the phenomenon of material conductivity changes upon light illumination, also known as photoconductive effect. Almost all photoelectric control applications are based on internal effect, such as photosensitive resistors, photosensitive diodes, photosensitive transistors, silicon photovoltaic cells, etc. Of course, in recent years, new photosensitive devices have emerged, such as: APD (avalanche photodiodes) with high-speed response and large amplification, semiconductor color sensors, photoelectric flow transistors, photograph tubes, CCD image sensors, etc., offered numerous possibilities for the further applications of photoelectric sensors.

This experiment mainly studies the V-I characteristics and light illumination characteristics of the four photosensitive sensors: photosensitive resistance, silicon photocell, photosensitive diode and photosensitive transistor.

This apparatus consists of adjustable  DC power supply (-12 ~ +12 V), adjustable power supply for light source, fully enclosed optical path, digital voltmeter for measurement, digital voltmeter for calibration, experimental circuits, calibrated silicon photocell, four to be tested photosensitive sensors, and so on.

The instruction manual contains comprehensive materials including experimental configurations, principles and step-by-step instructions. Please click Experiment Theory and Contents to find more information about this apparatus.

Main Specifications

Power supplyDC -12 V — +12 V adjustable, 0.3 A
Light source3 scales, continuously adjustable for each scale, max luminance > 1500 Lx 
Digital voltmeter for measurement3 ranges: 0 ~ 200 mV, 0 ~ 2 V, 0 ~ 20 V, resolution 0.1 mV, 1 mV and 10 mV respectively
Digital voltmeter for calibration0 ~ 200 mV, resolution 0.1 mV
Optical path length200 mm

Part List

Main Unit1
Photosensitive sensor1 set (with mount and calibration photocell, 4 sensors)
Incandescent bulb2
Connection wire8
Power cord1
Instruction manual1


Wiring schematic for testing photocell

(Click figure to enlarge)


V-I characteristics

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Illuminance characteristics

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