Electrical or electronic sensors and detectors are devices that measures or detects a real-world condition, such as motion, heat or light and converts the condition into an analog or digital representation. Sensors can be classified according to the type of energy transfer that they detect. Temperature sensors include temperature sensitive resistors (thermistors), thermometers, thermocouples, bi-metal thermometers and thermostats. Electrical resistance sensors, electrical current sensors, electrical voltage sensors, electrical power sensors, and magnetism sensors are electromagnetic sensors, which include ohmmeter, multimeter, galvanometer, ammeter, leaf electroscope, voltmeter, watt-hour meters, magnetic compass, fluxgate compass, magnetometer, and hall effect device. Mechanical sensors include pressure sensors (altimeter, barometer, barograph, pressure gauge, air speed indicator, rate of climb indicator, variometer), mechanical sensors (acceleration sensor, position sensor, selsyn, switch, strain gauge), and gas and liquid flow sensors (flow sensor, anemometer, flow meter, gas meter, water meter, mass flow sensor). Radar gun, speedometer, tachometer, odometer, occupancy sensor, and turn coordinator are motion sensors. Optical sensors (light sensors, or photodetectors) detects the intensity or brightness of light, or the intensity of red, green and blue for color systems. They include vacuum tube devices like photo-electric tubes, photomultiplier tubes; semiconductor devices such as photocells, photodiodes, phototransistors, CCDs, and Image sensors; and mechanical instruments such as the Nichols radiometer. Fire detectors generally work by flame sensing, temperature sensing, or smoke particle sensing. Various types of fire detectors are known. There are thermal detectors, ionization detectors, photoelectric detectors, light obscuration detectors, and radiation type (flame) detectors. Metal detectors are used in many industries for the detection of metal objects. In response to the challenge of the ever growing concern of counterfeiting, various instruments and detectors have been developed for detecting counterfeit currency. Radar detectors detect microwave signals from a traffic radar, sound an alert, and inform the driver of the strength of the microwave signals and sometimes location of the radar source.
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Monday, 22 January 2007 |
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Modern vehicles are equipped with electronic control systems to control the components based on information represented by output signals from various sensors for detecting operating conditions. There are a variety of electronic control systems, for example, an ABS (anti-lock brake system), a TCS (traction control system), an ESP (electronic stability program), etc. Vehicle speed sensors are used in motor vehicles to sense vehicle speed and send this information to the vehicle's onboard computer. Wheel speed sensors are typically mounted to a wheel support, such as a steering knuckle, for providing a pulsed speed signal to an antilock brake system. Electrical signals from wheel speed sensors are used by a controller to modulate pressure applied to the vehicle wheels to improve braking performance. |
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Wednesday, 17 January 2007 |
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Moisture detection is important in a variety of fields. Measurement of soil moisture is useful for minimizing the amount of irrigation water applied to growing plants, and for optimizing plant growth. Moisture meters can be used not only to measure a humidity in an atmosphere but also to automatically control humidifiers, dehumidifiers, air-conditioners for humidity adjustment. Humidity sensors can be classified into a resistance type humidity sensor and a capacitance type humidity sensor. A resistance type moisture sensor detects relative humidity by measuring the change in the resistance of an element corresponding to the ambient humidity. Capacitive moisture measuring elements deliver a capacitance value in dependence on the air humidity in the area around the measuring element. |
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Wednesday, 10 January 2007 |
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Accelerometers are sensors or transducers that measure acceleration. A typical accelerometer utilizes a proof mass, a spring joining the proof mass to a stationary housing or substrate, and a sensor to measure displacement of the proof mass. Accelerometers are now being manufactured with micro-electromechanical systems, which integrate mechanical elements, sensors and electronics on a common silicon substrate. MEMS accelerometers typically consist of a pendulous proof mass, a suspension system and a method for determining the relative motion of the proof mass under the influence of acceleration. Accelerometers find use in automobile suspension systems, vehicle air bag systems, vibrometers, computer hard disc drivers, and machine vibration monitors. |
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Thursday, 04 January 2007 |
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Tire pressure monitoring systems (TPMS) are used for the tires of motor vehicles to alert a driver when proper tire inflation is not being maintained. Proper tire inflation is important to increase tire life, maximize fuel economy, and optimize tire performance in terms of handling, braking distance, and tire integrity. A wireless tire pressure monitoring system is a direct measurement system that consists of an in-car display and an external (in-wheel) monitor signal transmission device. Such systems typically include a plurality of transmitters that measure a tire characteristic such as tire air pressure, and communicate data corresponding to the tire characteristic to the receiver. The communication link between the pressure sensor and the external receiver may be radio frequency (RF) signals. |
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Sunday, 17 December 2006 |
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Electric power steering systems are used extensively to reduce the manual steering effort or force needed to turn the steering wheel to thereby provide a comfortable steering touch to the driver. Torque measurement is performed to detect the torque caused to occur by a driver's operation using a steering wheel in an electromotive power steering system. The power steering system incorporates a torque sensor that detects a torque exerted on the steering shaft when the steering wheel is turned. Based on the torque detected by the torque sensor, a motor is actuated to assist the steering force. Many torque sensors are either a magnetostriction type, which uses the changes of magnetic property caused by strain, or an inductance type, which uses the changes of magnetic property caused by stress. |
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Monday, 11 December 2006 |
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A radiation detector converts radiation energy such as visible lights, infrared rays, ultraviolet rays, X-rays, gamma rays into electrical signals. Radiation detectors that utilize X-rays among various radiations are widely applied and developed in medical instruments, chemical analyzers and nondestructive inspection instruments. Radiation detectors include indirect conversion type detectors, and direct conversion type detectors. Radiation detectors may be designed and constructed to be sensitive to particular regions of the electromagnetic spectrum. Semiconductor radiation detectors typically have an entrance window electrode to receive impinging radiation. Semiconductor solid state radiation detectors have long been used in nuclear medicine, science and industry. |
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Tuesday, 05 December 2006 |
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Carbon monoxide detectors are consumer safety devices that monitor carbon monoxide (CO) levels. Carbon monoxide detection is important for health and safety concerns of human breathing. Carbon monoxide is an odourless, colourless, tasteless poisonous gas which can be produced by incomplete combustion of hydrocarbons. Carbon monoxide inhibits the blood's ability to carry oxygen to body tissue. Common sources of carbon monoxide include fires, gas appliances, heaters and furnaces, internal combustion engines used in power equipment and vehicles. Devices for sensing carbon monoxide and triggering an alarm in the presence of excessive concentrations of CO may utilize electrochemical sensors, semiconductor sensors, colorimetric detectors or IR (infra-red) detectors. |
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Tuesday, 21 November 2006 |
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An ultrasonic sensor is used for detecting distance by transmitting and receiving an ultrasonic wave. The distance between the sensor and an object is calculated on the basis of a signal obtained by reflected waves when the obstacle is to be detected by using the ultrasonic waves. Ultrasonic transducers are employed in various sensing devices such as distance meters, motion detectors or pen input devices. Transducers generally create ultrasonic vibrations through the use of piezoelectric materials such as certain forms of crystals or ceramic polymers. Ultrasound imaging systems include a transducer array connected to multiple channel transmit and receive beamformers. An ultrasonic flow sensor includes a flow probe that houses two ultrasonic transducers and a fixed acoustic reflector. |
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Tuesday, 14 November 2006 |
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Position sensing is used to electronically monitor the position or movement of a mechanical component. Magnetic position sensors are devices that generate an electronic signal output that is indicative of the relative position of a mechanical component. Non-contacting position sensors generate change to an electronically interrogated physical parameter that is proportional to the movement of a structure. Position measurements are widely implemented in industrial automation control. Linear/angular position sensors are used in automotive industry to determine the angular position of the steering column, the angular position of the throttle in engine control modules, the brake pedal position or the brake master cylinder position in brake-by-wire systems, and for vehicle smart suspension systems. |
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Saturday, 04 November 2006 |
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Radar detectors generally provide an alarm indication when a radar signal is received. Police radar detectors are devices for receiving and detecting signals generated by police radar units and generating an audible or visual warning signal in response thereto to provide early indication of the presence of the signals to the driver of an automobile. Speed detection systems are used to determine the speed of moving objects. A speed detection system which utilizes radar may generally be referred to as a so-called radar gun. It is often desirable for the automobile driver to know when the speed of the vehicle is being measured. The radar detector informs a car driver of the presence of the speed gun by detecting microwave signals from the speed gun and converting it into visual or acoustic signals. |
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Monday, 23 October 2006 |
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A pressure sensor may convert an amount of pressure into an electrical value. Pressures are measured by bringing the medium to be measured up to the sensor, or by transmitting the pressure prevailing in the medium to the sensor. Absolute pressure sensors measure a pressure relative to a vacuum and differential sensors measure a pressure difference between two inputs. A semiconductor pressure sensor includes a semiconductor substrate, a diaphragm and diffusion gauge resistors. Piezoresistive pressure sensor is formed by diffusing impurities onto a semiconductor and has advantages of easy fabrication and superior linearity. Capacitive pressure sensors measure pressure by the capacitive changes resulting from variations in the distance between a movable diaphragm and a substrate. |
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Monday, 16 October 2006 |
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A motion detector is an electronic device that detects the physical movement in a given area and transforms motion into an electric signal. Motion sensors are used in a wide variety of applications and as a result many different types of motion sensors are available. Motion detectors are mainly used in for security systems. A passive infrared motion detection system detects heat energy radiated or emitted by an object. Infrared motion detector devices are often used in automatic light switches and security systems to turn on a light or to activate some other form of alarm or warning indicator when a person or motor vehicle enters a monitored area. Radar motion detectors emit a continuous wave microwave signal and compare the emitted and echo frequencies to produce a beat frequency. |
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Friday, 06 October 2006 |
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The sensing of temperature is one of the fundamental requirements in almost every application. Various types of temperature sensors are known including thermometers, resistance temperature detectors, thermocouples, and radiometers. Typical integrated circuit (IC) solutions for sensing temperature change use a semiconductor temperature sensor. Temperature sensors are utilized in a wide variety of applications in which it is necessary to monitor the temperature within a space. Computer systems rely on temperature sensors located in the proximity of the processor package to provide temperature information for thermal control. Temperature sensors are used to monitor a variety of automotive systems, including for example coolant temperature and exhaust gas temperature. |
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Monday, 18 September 2006 |
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Driver assistance systems require a sensor system with which information concerning the vehicle's vicinity may be sensed. Parking for vehicles is facilitated, monitored and controlled by using sensors or detectors to determine the availability of vacant parking spaces and by indications to alert vehicle operators at a substantial distance of the availability a vacant space. A radar detector is effective at long distances, and is good at detecting speed and range information. Radars detectors are classified into various systems according to the waveforms of radio waves in use. An image processing sensors excel in identifying smaller obstructions closer to the vehicle. The ultrasonic sound sensors sense the immediate surroundings of motor vehicles in order to assist the driver during a parking maneuver. |
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Thursday, 07 September 2006 |
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Automotive vehicles with an internal combustion engine have an exhaust system including a pathway for exhaust gas to move away from the engine. Effective emission control of exhaust gases with a catalytic converter requires precise control of the air/fuel ratio supplied to the engine cylinders. Oxygen sensors are provided to control air/fuel ratio based on measured concentrations of oxygen in the exhaust gas for feedback. Accurate feedback from the oxygen sensor to the fuel metering system is essential for proper regulation of the level of pollutants in exhaust gases. Optimizing the fuel/air mixture changes the combustion conditions and achieves more complete combustion. Oxygen sensors provide a voltage output that varies in accordance with the amount of oxygen in the combustion product. |
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Monday, 21 August 2006 |
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A smoke detector can warn of a smoldering fire before any significant property damage occurs. Smoke detectors detect the presence of smoke particles as an early indication of fire. In general, smoke detectors are based on the principle of detecting smoke particles in the air. Fire or smoke detecting systems generally include individual detecting units that operate relatively independently of central control. Modern smoke detection is usually based on either an ionization or a photoelectric detection technology. The photoelectric detector responds to changes in light transmission through a medium that contains smoke. The ionization smoke detector responds to changes in the conductivity of an ionized medium due to the presence of combustion products. |
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Sunday, 20 August 2006 |
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Metal detectors are used in the security field, for checking passengers at airports and for checking visitors in particularly highly protected buildings or installations. The metal detectors typically employ a transmit coil through which current flows. A receive coil is employed to measure a change in the field thus producing a detection signal. Metal detectors identify the type of a metal object located in a background environment by analyzing the characteristics of an electrical signal attributable to the target. Metal detectors are based on the measurement of changes to the electromagnetic field. An electromagnetic field is created in a given region where a hidden object may be located. The metal detector has circuitry that transmits a periodic signal to the transmit coil. |
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Sensors and Detectors
