A sensor is a device that measures a particular characteristic of an object or system. Some sensors are purely mechanical, but most sensors are electronic, returning a voltage signal that can be converted into a useful engineering unit. Sensors take advantage of the mechanical or electrical response of its components to relate the response to a relevant quantity. Engineers use sensors in test and monitoring applications, but homeowners interact with sensors every day. Automobiles are filled with sensors, from the engine to the airbag.
Electrical sensors examine the change in electrical or magnetic signals based on an environmental input. Examples of electrical sensors are metal detectors, RADAR systems and even simple electrical meters such as voltmeters and ohmmeters. Magnetometers are widely used in traffic intersections to detect the presence of a vehicle.
Mechanical sensors measure the change in a mechanical property of an object or system. The primary mechanical sensor is the strain gauge, which forms the basis of several different types of mechanical sensors. A strain gauge is a variable resistor that measures the amount of deformation that a part endures when it is affected by a force. Strain gauges form the basis of load cells, humidity sensors and pressure transducers. Another common mechanical sensor is the potentiometer, which measures angular or linear displacement.
Optical sensors use principles of light to quantify object characteristics. The most common optical sensor is the electric eye, which uses a beam of light to detect the presence of an object. Optical sensors also include sensing light outside of the visible spectrum, such as infrared or ultraviolet. Fiber-optic sensors use the properties of light traveling through a glass fiber to measure a wide variety of characteristics, such as temperature and strain. Photodetectors and motion detectors act as switches to turn lighting systems on and off.
Chemical sensors measure the presence and quantity of a specific chemical in an environment. Some chemical sensors include radon and carbon monoxide detectors, automobile oxygen sensors and pH sensors. Some chemical sensors are designed to detect a specific compound or ion for specialized testing operations.
Temperature sensors simply report the temperature of a part or environment. The most common type of temperature sensor is the thermocouple, which relies on voltage changes based on dissimilar metal junctions. Thermocouples are available for a wide range of temperatures, from ambient environmental temperatures through high temperature environments, such as jet engines.
- Photo Credit Image by Flickr.com, courtesy of Steve Jurvetson
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