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Sheathed thermocouple - Principles and Applications of Ceramic Pressure Sensor


Corrosion-resistant ceramic pressure sensor does not pass the liquid , the pressure acts directly on the front surface of the ceramic diaphragm, the diaphragm to produce a slight deformation , thick film resistors printed on the back of the ceramic diaphragm , connected into a Wheatstone bridge ( closed bridge ) , the piezoresistive effect of varistors make the bridge to produce a highly linear proportional to the pressure , and the excitation voltage is proportional to the voltage signal , the signal depending on the calibration standard pressure range of 2.0 / 3.0 / 3.3 mV / V , etc., can be compatible and strain sensors . Laser calibration, the sensor has high temperature stability and stability with time , temperature compensation sensor comes 0 ~ 70 ℃, and the majority and may directly contact the medium. Ceramic is a recognized high elasticity, material corrosion , abrasion , impact and vibration. Thermal stability characteristics of ceramic thick film resistor and it can make it up to operating temperature range of -40 ~ 135 ℃, but also has high accuracy, high stability of the measurement . Electrical Insulation degree > 2kV, the output signal is strong, long-term stability . High characteristics, low prices will be the development direction of the ceramic sensor pressure sensor , a comprehensive alternative to other types of sensors trend in Europe and America , in China , more and more users use ceramic sensor replacement diffused silicon pressure sensor.

Currently on the market sensor ( thermocouples ) species -rich and diverse, which makes the design engineer can select the desired system pressure sensor. These sensors include both basic converter , but also more complex , highly integrated sensor with on-chip circuitry. Because of these differences, the design engineer must be possible to compensate the measurement error of the pressure sensor , which is an important step in the design and application of sensors to meet the requirements of the guarantee. In some cases , compensating sensor applications can improve overall performance .

Many types of mechanical sensors , such as resistance strain gauge pressure sensors, semiconductor strain gauge pressure sensors, piezoresistive pressure sensors, pressure sensors inductive , capacitive pressure sensors, pressure sensors and resonant capacitive acceleration sensors. But the most widely used is the piezoresistive pressure sensor, which has a very low price and high accuracy and good linearity.

Understanding piezoresistive force sensor, we first learn what resistance strain gauges such elements . Resistance strain gauge is a change in the strain on the DUT converted into an electrical signal sensitive device. It is one of the main components of piezoresistive strain sensors. Resistance strain gauge is the most widely used metal resistance strain gauges and semiconductor strain gauges two kinds. Metal resistance strain gauges have filamentous strain gauge and metal foil strain gages two kinds. The strain gauges are usually tightly bonded through a special stick and agents produce the mechanical strain on the substrate , the substrate stress when stress occurs , the resistance strain gauges are deformed together , so that the resistance strain gauge changes, so that the the voltage across the resistor is changed . This change in resistance in the strain gauge force generated by the generally smaller and are generally composed of such a strain gage bridge, and the subsequent amplification by an instrumentation amplifier , and then transmitted to the processing circuit ( typically A / D converter and CPU) display or actuators.

Metal resistance strain gauge internal structure :

It consists of materials, metal foil strain or strain wire , insulation sheet and lead other parts of the matrix components. Depending on the use , the resistance of the resistance strain gauge can be designed by a designer , it should be noted that the range of resistance : the resistance is too small , the required drive current is too large , resulting in a strain gauge while the heating temperature itself, different environments, so much change in resistance strain gauge output zero drift significantly , nulling circuit too complicated. The resistance is too large, the impedance is too high, poor resistance to external electromagnetic interference . Europe in general are tens to tens of kilohms .

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