An Introduction to Sensors
How Engineers Use Sensors to Measure Object Properties and Behaviors
Electrical and mechanical sensors are widely used to characterize the performance and properties of components and systems, but are also found in household objects.
Sensors are electrical or mechanical components that are used to measure a property or behavior of an object or system. Some sensors measure properties directly, other sensors measure properties indirectly, using conversions or calculations to determine results. Sensors are used by scientists and engineers during research and testing activities, but they can also be found in many household objects, such as temperature sensors in an oven to accelerometers in an automobile airbag system. Sensors are generally categorized by the type of phenomenon that they measure, rather than the functionality of the sensor itself.
Mechanical Sensors
Mechanical sensors measure a property through mechanical means, although the measurement itself may be collected electronically. An example of a mechanical sensor is a strain gauge. The strain gauge measures the physical deformation of a component by experiencing the same strain as the component, yet the change in resistance of the strain gauge is measured electrically. Other types of mechanical sensors include:
- Pressure sensors
- Accelerometers
- Potentiometers
- Gas and fluid flow meters
- Humidity sensors
Electrical
Electrical sensors measure electric and magnetic properties. An example of an electrical sensor is an ohmmeter, which is used to measure electrical resistance between two points in a circuit. An ohmmeter sends a fixed voltage through one probe, and measures the returning voltage through a second probe. The drop in voltage is proportional to the resistance, as dictated by Ohm's Law. Other electrical sensors include:
- Voltmeter/Ammeter
- Metal detector
- RADAR
- Magnetometer
Thermal
Although all thermal sensors measure changes in temperature, there are a variety of types of thermal sensors, each with specific uses, temperature ranges, and accuracies. Some types of thermal sensors include:
- Thermometers
- Thermocouples
- Thermistors
- Bi-metal thermometers
Chemical
Chemical sensors generally detect the concentration of a substance in the air or in a liquid. Some chemical sensors, such as pH glass electrodes are designed to be sensitive to a certain ion. Some other types of chemical sensors include:
- Oxygen sensors
- Carbon monoxide detectors
- Redox electrodes
Optical
Optical sensors detect the presence of light waves. This could include light in the visible spectrum, or outside the visible spectrum, in the case of infrared sensors. Some types of optical sensors include:
- Photodetectors
- Infrared sensors
- Fiberoptic sensors
- Interferometers
Other Types of Sensors
There are many other types of sensors that don't fall into one of the broad categories described here. Some of these sensors include:
- Radiation sensors, including Geiger counters and dosimeters
- Motion sensors, including radar guns and speedometers
- Acoustic, including sonar and seismometers
- Gyroscopes
While sensors are used frequently by engineers and scientists in their studies, sensors are also use in many household products. Sensors can be found in many everyday objects, including touch-sensitive buttons and screens, infrared remote controls, motion-sensitive lighting, and home thermostats.
Sources
Sensors Portal website
Omega Engineering website
