Red Seal Instrumentation and Control Technician Practice Exam

What type of sensor detects changes in light intensity?

1. Pressure sensor

2. Photoelectric sensor

3. Thermal sensor

4. Ultrasonic sensor

The correct answer is: Photoelectric sensor

A photoelectric sensor is designed specifically to detect changes in light intensity. This type of sensor works by using a light source (typically a laser or LED) and a photodetector. When an object interferes with the light beam or changes the amount of light that reaches the detector, the sensor interprets these changes and produces an output signal. Photoelectric sensors are widely used in various applications, such as automation systems, safety systems, and object detection, due to their sensitivity to light levels and their ability to operate without physical contact with the object being detected. These sensors can detect not just the presence or absence of objects but also their distance and speed, depending on the design and functionality. Other sensor types, such as pressure sensors, thermal sensors, and ultrasonic sensors, are designed to measure physical phenomena other than light intensity. Pressure sensors detect changes in pressure within a system; thermal sensors measure temperature changes, and ultrasonic sensors use sound waves to measure distances or detect objects. Therefore, they would not be suitable for detecting variations in light intensity.