传感器专业名词英文解释.doc

1. Briefly define the following terms1) TransducerA transducer is a device that converts a signal from one physical form to a corresponding signal having a different physical form .2) SensorA sensor converts a physical signal into an electrical signal (i.e., a microphone).3) ActuatorAn actuator is a device that converts electrical energy into physical energy (i.e., a loudspeaker).4) LinearityThe linearity describes the closeness between the calibration curve and a specified straight line. 5) SensitivityThe sensitivity is defined in terms of the relationship between input physical signal and output electrical signal. It is generally the ratio between a small change in electrical signal to a small change in physical signal. The sensitivity is the slope of the calibration curve.6) HysteresisThe hysteresis refers to the difference between two output values that correspond to the same input, depending on the direction (increasing or decreasing) of successive input values. That is, similarly to the magnetization in ferromagnetic materials, it can happen that the output corresponding to a given input depends on whether the previous input was higher or lower than the present one.Some sensors do not return to the same output value when the input stimulus is cycled up or down. The width of the expected error in terms of the measured quantity is defined as the hysteresis. 7) RepeatabilityThe repeatability is the closeness of agreement between successive results obtained with the same method under the same conditions and in a short time interval. sample standard deviation8) Strain (mechanical)Fractional change in length L/L.9) Gage factorThe gage factor is defined as the fractional change in resistance divided by the strain.10) Piezoresistive effect The change in resistivity as a result of a mechanical stress is called the piezoresistive effect.11) direct piezoelectric effect. the phenomenon of generation of a voltage under mechanical stress is referred to as the piezoelectric effect.12) converse piezoelectric effect. The mechanical strain produced in the crystal under electric stress is called the converse piezoelectric effect. 13) Numerical ApertureThe acceptance cone defines how much light will be accepted into the fiber and ultimately how much remains in the fiber, and is referred to as the numerical aperture. 14) Extrinsic sensorThe optical fiber plays no part in achieving the modulating but simply acts as a transmission medium ; these are extrinsic sensors.15) Intrinsic sensors (fiber optic sensor)The optical fiber plays a major role in modulating the energy from the source; these are referred to as intrinsic sensors.16) Humiditya quantity representing the amount of water vapor in the atmosphere or a gas17) Absolute humidityAbsolute humidity is the mass of water vapor per unit volume of air.18) Relative humidityThe ratio of the actual vapor density to the theoretical maximum (saturation) vapor density at the same temperature, expressed as a percentage. The relative humidity is the ratio of the actual vapor pressure to the saturation vapor pressure at given temperature.19) Peltier effectWhen two dissimilar metals are connected together, a small voltage called a thermojunction voltage is generated at the junction. This is called the Peltier effect.20) Law of Homogeneous Conductors For a given pair of homogeneous conductors forming a closed loop, the Seebeck emf depends only on the temperatures of the junctions, and not on the temperature distribution along the length of the conductors.21) Law of intermediate metals A third (intermediate) metal wire can be inserted in series with one of the wires without changing the voltage reading (provided that the two new junctions are at the same temperature).If there is a third metal introduced into the thermocouple circuit , it will not adversely effect the reading, if and only if the two junctions of the third metal are at the same temperatures .22) Bernoullis theorem Bernoullis equation states that energy is approximately conserved across a constriction in a pipe.Bernoullis equation: P/(g) + v2/g + y = constant (=density; g=acceleration of gravity ; v=fluid velocity; y=elevation )2. Describe the following devices and how they work1) Strain gageThe strain gauge usually consists of wire, baking, thinpaper, and lead welded. The wire is arranged in the form of a grid in order to obtain higher resistances. 2) Parallel plate Capacitive SensorThe parallel plate Capacitive Sensor is a function of the distance d (cm) between the electrodes of a structure, the surface area A (cm2) of the electrodes, and the permittivity 0 (for air) of the dielectric between the electrodes; therefore: 3) Differential Capacitive SensorA differential capacitor consists of two variable capacitors so arranged that they undergo the same change, but in opposite directions. The amplifier circuit, depending on its configuration, can generate a voltage proportional to C1 - C2 or C1/C2 or (C1 - C2)/(C1 + C2).4) Variable Reluctance SensorsA typical single-coil variable-reluctance displacement sensor is illustrated in the Figure below. The sensor consists of three elements: a ferromagnetic core, a variable air gap, and a ferromagnetic plate.Based on change in the reluctance of a magnetic flux path. Self-inductance L of the coil is:Reluctance can be given as: 5) Variable-Reluctance TachogeneratorsIt consists of a ferromagnetic, toothed wheel attached to a rotating shaft, a coil and a magnet. The wheel rotates in close proximity to the pole piece, thus causing the flux linked by thecoil to change. The sensors output depends on the speed of the rotation of the wheel and the number of teeth.6) LVDTAn LVDT consists of three coils, a form and a core. The coils are wound on a hollow form. The primary is excited by some ac source. Flux formed by the primary is linked to the two secondary coils, inducing an ac voltage in each coil. A core is inside the former. It can slide freely through the center of the form.In many applications, the two secondary coils are connected in series opposition. Then the two voltages will subtract; that is, the differential voltage is formed. When the core is centrally located, the net voltage is zero. When the core is moved to one side, the net voltage will increase.7) Compression Mode Piezoelectric AccelerometersUpright compression designs sandwich the piezoelectric crystal between a seismic mass and rigid mounting base. A pre- load stud or screw secures the sensing element to the mounting base.When the sensor is accelerated, the seismic mass increases or decreases the amount of compression force acting upon the crystal, and a proportional electrical output results.8) Shear mode accelerometer Shear mode accelerometer designs bond, or “sandwich,” the sensing material between a center post and seismic mass. A compression ring or stud applies a preload force required to create a rigid linear structure. Under acceleration, the mass causes a shear stress to be applied to the sensing material. This stress results in a proportional electrical output by the piezoelectric material. They represent the traditional or historical accelerometer design.9) PsychrometerA psychrometer contains two identical thermometers. One sensor, the dry bulb , measures the ambient temperature. The other sensor, the wet bulb, is in a wetted condition. In operation, water evaporation cools the wetted thermometer, resulting in a measurable difference between it and the ambient, or dry bulb measurement. When the wet bulb reaches its maximum temperature depression, the humidity is determined by comparing the wet bulb/dry bulb temperatures on a psychrometric chart10) Dunmore sensorThe Dunmore sensor uses a dilute lithium chloride solution in a polyvinyl acetate binder on an insulating substrate. The resistance of the sensor, measured between a bifilar grid, is a function of the r.h. of the surrounding air. 11) MOS Capacitor CCDs are typically fabricated on a p-type substrate. In order to implement the “buried” channel a thin n-type region is formed on its surface. A insulator, in the form of a silicon dioxide layer is grown on top of the n-region. The capacitor is finished off by placing one or more electrodes, also called gates, on top of the insulating silicon dioxide.12) Full frame transfer (FFT)It consists of a parallel CCD shift register, a serial CCD shift register and a signal sensing output amplifierThe image pixel are vertically transferred into a horizontal serial register, and the charges are horizontally shifted out.13) Interline transfer (ILT)The readout regions are interspaced between the imaging regions, and are shielded from the light. At the end of the integration period, the charges are transferred horizontally to the vertical readout registers in parallel, and then read out line-by-line in a manner similar to FFT.ILT does avoid smear but with the cost of the sensitive imaging areas.14) Frame transfer (FT) The array is grouped into two sections: the image section and the storage section. These two sections are identical, except that the storage section is shielded from the light. During the readout, charges are transfered line-by-line into the storage section by applying the same clocking to both sections. At the end of the integration period, charges in the storage section are transferred line-by-line a manner similar to FFT. 15) proximity sensors Proximity sensors detect objects that are near but without touching them. These sensors are used for near-field robotic operations.16) Time-of-flight sensorsTime-of-flight sensors estimate the range by measuring the time elapsed between the transmission and return of a pulse17) Triangulation sensorsTriangulation sensors measure range by detecting a given point on the object surface from two different points of view at a known distance from each other. Knowing this distance and the two view angles from the respective points to the aimed surface point, a simple geometrical operation yields the range.18) Thermal Infrared DetectorsThermal infrared detectors convert incoming radiation into heat, raising the temperature of the thermal detector.19) Photon-type detectors Photon-type detectors react to the photons emitted by the object. The infrared radiation causes changes in the electrical properties of photon-type detectors.There are two main types of photon infrared detectors. One is called Photoconductive detector, which exhibit increased conductivity with received radiation. Another is named as Photovoltaic detector, this device converts received radiation into electric current.20) shock tube Construction of a shock tube is quite simple: it consists of a long tube, closed at both ends, separated into two chambers by a diaphragm, as shown in the Fig. below. A pressure differential is built up across the diaphragm, and the diaphragm is burst, either directly by the pressure differential or initiated by means of an externally controlled probe. Rupturing of the diaphragm causes a shock wave.The shock tube provides the nearest thing to a transient pressure “standard.”21) ThermocoupleA thermocouple consists of two electrical conductors made of different metals that are joined at one end.Note particularly that two junctions are always required. In general, one sense the desired or unknown temperature; this one we shall call the hot or measuring junction. The second will usually be maintained at a known fixed temperature; this one we shall refer to as the cold or reference junction. When the two junctions are at different temperatures, a voltage is developed across the junction.22) Bimetallic strip thermometerTwo dissimilar metals are bonded together into what is called a bimetallic strip. Since two metals have different coefficient of thermal expansion, one metal will expands more than does another metal as temperature increases, causing the bimetallic strip to curl upwards as sketched.23) RTDA resistance temperature detector is basically either a long, small diameter metal wire wound in a coil or an etched grid on a substrate, much like a strain gage. The resistance of an RTD increases with increasing temperature.24) Three-wire BridgeA clever circuit designed to eliminate the lead wire resistance error is called a three-wire RTD bridge circuit, as sketched to the right.If wires A and B are perfectly matched in length (wires A and B have the same length, and thus the same resistance,), their impedance effects will cancel because each is in an opposite leg of the bridge. The third wire, C, acts as a sense lead and carries no current.25) ThermistorA thermistor is similar to an RTD, but a semiconductor material is used instead of a metal. A change in temperature causes the electrical resistance of the semiconductor material to change. Positive temperature coefficient (PTC) and and negative temperature coefficient (NTC) units are available.26) Seismic (Absolute) Acceleration Pickups It consistis of a mass, a spring, and a damper arrangement, as shown in the Figure below. Fig.y(t）= the absolute displacement of the mass Mx(t）= the absolute displacement of the basez the relative motion between the mass and the basem massc damping constantk spring constantSeismic (Absolute) Displacement Pickups The relative displacement z (the output of the sensor) is proportional to the applied displacement. A low value of n is needed (n should be much less than the lowest vibration frequency for accurate displacement measurement. )Seismic Accelerometer The relative displacement z ( the output of the sensor) is proportional to the applied acceleration. a high n is needed to measure accurately high-frequency. Increasing n will increase the range of frequency for which the amplitude-ratio curve is relatively flat; 27) Seismic Velocity Pickup (moving coil type) One type of velocity transducer is based on a linear generator. When a coil cuts the magnetic field lines around a magnet, a voltage is induced in the coil, and this voltage is dependent on the speed of the coil relative to the magnet. The velocity pickup is designed like a displacement pickup, to have a low value of wn and to operate at angular frequencies well above wn so that the motion of the seismic mass is virtually the same as that of the casing but (almost) opposite in phase. 28) The Orifice Plate FlowmetersAn orifice plate is a restriction with an opening smaller than the pipe diameter which is inserted in the pipe; Because of the smaller area the fluid velocity increases, causing a corresponding decrease in pressure.The flow ratee can be