A sensor is a device that detects or measures input signals from surrounding environments and provides corresponding output signals. An input signal could be a variation in moisture, pressure, temperature, electric or magnetic field. It is firstly captured by a sensor and then converted to a readable signal. Most of the time, output signals are usually communicated with electronic devices to be easily read, processed, displayed and transmitted.
There are many types of sensors based on measured targets, such as temperature sensor, pressure sensor, humidity sensor, motion sensor, proximity sensor, gas sensor, biosensors and many more. Here let’s take a brief look at what each type of sensors does.
Temperature sensor is a device to gather temperature information of surrounding environments and convert the information to readable data. There are two basic physical types for temperature sensor: contact temperature sensor and non-contact temperature sensor. Contact temperature sensor requires a physical contact with the target being measured and can be used to measure the temperature of solids, liquids and gases. Non-contact temperature sensor measures heat radiation from an object and does not require a physical contact. Three most well known temperature sensors are thermistors, resistance temperature detectors (RTDs) and thermocouples. Temperature sensors have wide applications, such as HVAC control, food processing, medical applications and biology research etc.
Pressure sensor is a device that measures pressure and generates an electric signal that depends upon the external pressure imposed. Pressure sensing could be achieved through different technologies, including capacitive method, piezoelectric method, optical method and potentiometric method etc. Pressure sensors have been widely used in many applications, such as automotive industry, marine industry, aviation, air conditioning, etc.
Humidity sensor is able to sense the presence of water in air in a given space. Humidity can affect human comfort as well as manufacturing processes, so it is important to know the humidity information in many industrial and domestic applications. Different methods are used to measure humidity, such as capacitive method, resistive method, thermal method and gravimetric method etc. Humidity sensors are widely used in semiconductor industry, medical applications and agriculture etc.
Motion sensor is a sensor device used to detect moving objects. These sensors are the building blocks components in advance security systems, home control, automated lightning systems and other automated system used in industries. Motion sensing could be achieved through different technologies, such as infrared, microwave, ultrasonic and optics etc. The motion sensors are widely employed in commercial applications and can be found in almost every field of latest electronics including smartphone, wearable electronics, playstation and virtual reality etc.
Proximity sensor detects objects in its vicinity. It measures the target object without touching it, thus there is no physical contact. The sensor generally emits electromagnetic radiation and then detects the object proximate to it by getting a return signal and measuring the time delay. Proximity sensors comprise six main groups, according to principles of operation: optical, capacitive, resistive, magnetic, ultrasound, and air pressure. Each of these sensors can measure numerous physical properties and are extensively used in various applications. Proximity sensors are used in broad applications, including consumer electronics, robotics, driverless cars and space applications etc.
Gas Sensor is a sensor device used for the detection and presence of a certain gas in an area and is mostly used for safety concern. This sensor is among the top priority in the industry as some gases are harmful and can cause dangerous effects on human bodies. Some frequently used sensors include infrared sensor, metal-oxide-semiconductor sensor, electrochemical sensor, catalytic sensor, chemresistor, acoustic method based sensor and sensor using photoionization method. Gas sensors have wide applications starting from gas detection and hazardous gas monitoring in the industry to gas detection and monitoring in small commercial parking or service garages, to pharmaceutical and petrochemical facilities.
Biosensor is a device made up of a transducer with biological recognition characteristics for elements such as DNA, enzymes, antibodies, and cells etc. The main principle of operation is that the signal produced by the transducer is directly related to the concentration or change in concentration of a recognition element in biological domain. The technologies used in biosensors include electrical, optical, electrochemical, magnetic, thermometric, piezoelectric, or micromechanical transducing microsystem etc. Biosensors have many applications in fields such as the environment, biomedical research, medicine, drug discovery, food safety and hazard, process industries, security and even defense.