发布时间 : 星期一 文章测控技术与仪器专业毕业设计外文翻译更新完毕开始阅读6939be57ad02de80d4d8407f
Development of Sensor New Technology
Sensor is one kind component which can transform the physical quantity, chemistry quantity and the biomass into electrical signal. The output signal has the different forms like the voltage, the electric current, the frequency, the pulse and so on, which can satisfy the signal transmission, processing, recording, and demonstration and control demands. So it is the automatic detection system and in the automatic control industry .If automatic Technology is used wider, then sensor is more important. Several key words of the sensor： 1 Sensor Elements
Although there are exception ,most sensor consist of a sensing element and a conversion or control element. For example, diaphragms,bellows,strain tubes and rings, bourdon tubes, and cantilevers are sensing elements which respond to changes in pressure or force and convert these physical quantities into a displacement. This displacement may then be used to change an electrical parameter such as voltage, resistance, capacitance, or inductance. Such combination of mechanical and electrical elements form electromechanical transducing devices or sensor. Similar combination can be made for other energy input such as thermal. Photo, magnetic and chemical,giving thermoelectric, photoelectric,electromaanetic, and electrochemical sensor respectively. 2 Sensor Sensitivity
The relationship between the measured and the sensor output signal is usually obtained by calibration tests and is referred to as the sensor sensitivity K1= output-signal increment / measured increment . In practice, the sensor sensitivity is usually known, and, by measuring the output signal, the input quantity is determined from input= output-signal increment / K1. 3 Characteristics of an Ideal Sensor
The high sensor should exhibit the following characteristics.
(a)high fidelity-the sensor output waveform shape be a faithful reproduction of the measured; there should be minimum distortion.
(b)There should be minimum interference with the quantity being measured; the presence of the sensor should not alter the measured in any way.
(c)Size. The sensor must be capable of being placed exactly where it is needed.
(d)There should be a linear relationship between the measured and the sensor signal. (e)The sensor should have minimum sensitivity to external effects, pressure sensor,for example,are often subjected to external effects such vibration and temperature. (f)The natural frequency of the sensor should be well separated from the frequency and harmonics of the measurand.
Sensors can be divided into the following categories： 1 Electrical Sensor
Electrical sensor exhibit many of the ideal characteristics. In addition they offer high sensitivity as well as promoting the possible of remote indication or mesdurement.
Electrical sensor can be divided into two distinct groups: (a)variable-control-parameter types,which include: (i)resistance (ii)capacitance (iii)inductance
(iv)mutual-inductance types
These sensor all rely on external excitation voltage for their operation. (b)self-generating types,which include (i)electromagnetic (ii)thermoelectric (iii)photoemissive (iv)piezo-electric types
These all themselves produce an output voltage in response to the measurand input and their effects are reversible. For example, a piezo-electric sensor normally produces an output voltage in response to the deformation of a crystalline material; however, if an alternating voltage is applied across the material, the sensor exhibits the reversible effect by deforming or vibrating at the frequency of the alternating voltage.
2 Resistance Sensor
Resistance sensor may be divided into two groups, as follows:
(i)Those which experience a large resistance change, measured by using potential-divider methods. Potentiometers are in this group.
(ii)Those which experience a small resistance change, measured by bridge-circuit methods. Examples of this group include strain gauges and resistance thermometers.
3 Capacitive Sensor
The capacitance can thus made to vary by changing either the relative permittivity, the effective area, or the distance separating the plates. The characteristic curves indicate that variations of area and relative permittivity give a linear relationship only over a small range of spacings. Thus the sensitivity is high for small values of d. Unlike the potentionmeter, the variable-distance capacitive sensor has an infinite resolution making it most suitable for measuring small increments of displacement or quantities which may be changed to produce a displacement. 4 Inductive Sensor
The inductance can thus be made to vary by changing the reluctance of the inductive circuit.
Measuring techniques used with capacitive and inductive sensor: (a)A.C. excited bridges using differential capacitors inductors. (b)A.C. potentiometer circuits for dynamic measurements.
(c)D.C. circuits to give a voltage proportional to velocity for a capacitor.
(d)Frequency-modulation methods, where the change of C or L varies the frequency of an oscillation circuit.
Important features of capacitive and inductive sensor are as follows: (i)resolution infinite
(ii)accuracy±0.1% of full scale is quoted (iii)displacement ranges 25*10-6 m to 10-3m (iv)rise time less than 50us possible
Typical measurands are displacement, pressure, vibration, sound, and liquid level. 5 Linear Variable-differential Ttransformer 6 Piezo-electric Sensor 7 Electromagnetic Sensor 8 Thermoelectric Sensor 9 Photoelectric Cells
10 Mechanical Sensor and Sensing Elements
In information age, the information industry includes information gathering, transmission, process three parts, namely sensor technology, communication, computer technology. Because of ultra large scale integrated circuit’s rapid development after having been developed Modern computer technology and communication, not only requests sensor precision reliability, speed of
response and gain information content request more and more high but also requests its cost to be inexpensive. The obvious traditional sensor is eliminated gradually because of the function, the characteristic, the volume, the cost and so on. As world develop many countries are speeding up to the sensor new technology’s research and the development, and all has obtained the enormous breakthrough. Now the sensor new technology development mainly has following several aspects:
Using the physical phenomenon, the chemical reaction, the biological effect as the sensor principle therefore the researches which discovered the new phenomenon and the new effect are the sensor technological improving ways .it is important studies to developed new sensor’s the foundation. Japanese Sharp Corporation uses the superconductivity technology to develop successfully the high temperature superconductivity magnetic sensor and get the sensor technology significant breakthrough. Its sensitivity is so high and only inferior in the superconductivity quantum interference component. Its manufacture craft is far simpler than the superconductivity quantum interference component. May use in magnetism image formation technology. So it has the widespread promoted value.
Using the immune body and the antigen meets one another compound when the electrode surface. It can cause the electrode potential change and use this phenomenon to be possible to generate the immunity sensor. The immunity sensor makes with this kind of immune body may to some organism in whether has this kind of ant original work inspection. Like may inspect somebody with the hepatitis virus immune body whether contracts the hepatitis, plays to is fast, the accurate role. The US UC sixth branch has developed this kind of sensor.
The sensor material is the important foundation for sensor technology, because the materials science is progressive and the people may make each kind of new sensor For example making the temperature sensor with the high polymer thin film; The optical fiber can make the pressure, the current capacity, the temperature, the displacement and so on the many kinds of sensors; Making the pressure transmitter with the ceramics. The high polymer can become the proportion adsorption and the release hydrogen along with the environment relative humidity size. The high polymer electricity lies between