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Working principle of pressure transducer
Nov 01, 2018

1 Introduction

Pressure sensors are one of the most commonly used sensors in industrial practice. Generally, the output of a common pressure sensor is an analog signal, or the output is a digital signal during a continuous time interval. The commonly used pressure sensors are mainly made by the piezoelectric effect, and such sensors are also called piezoelectric sensors.

2. Classification of pressure sensors

There are many types of pressure sensors, mainly strain gauge pressure sensors, ceramic pressure sensors, diffused silicon pressure sensors, sapphire pressure sensors, piezoelectric pressure sensors, etc. Below I will introduce the operating principles of these types.

3. Strain gauge Pressure sensor working principle

Some of the center of the strain gauge pressure sensor is a strain gauge. When the wire is subjected to an external force, its length and cross-sectional area will change. From the above formula, it can be easily seen that the resistance value will change, assuming metal. When the wire is stretched by an external force effect, its length is added, and the cross-sectional area is reduced, and the resistance value is increased. When the wire is tightened by the external force effect, the length is reduced and the cross section is added, and the resistance value is decreased. It is only necessary to measure the change in the resistance (generally the voltage at both ends of the measuring resistor) to obtain the strain of the strained wire.

4. Ceramic pressure sensor working principle

Principle of ceramic pressure sensor: The corrosion-resistant ceramic pressure sensor has no liquid transfer. The direct effect of the pressure on the front surface of the ceramic diaphragm makes the diaphragm undergo small deformation. The thick film resistor is printed on the opposite side of the ceramic diaphragm and connected into a benefit. The Stern Bridge (closed bridge), because of the piezoresistive effect of the varistor, causes the bridge to have a high linearity proportional to the pressure and a voltage signal proportional to the encouraged voltage. The normalized signal is calibrated according to the pressure range. It is compatible with strain gauge sensors for 2.0 / 3.0 / 3.3 mV / V and so on. After laser calibration, the sensor has high temperature stability and time stability. The sensor has a temperature of 0 to 70 °C and can be directly touched with most media.

5. Diffused silicon pressure sensor working principle

Working principle: the pressure of the measured medium directly affects the diaphragm of the sensor (stainless steel or ceramic), causing the diaphragm to undergo a micro-displacement proportional to the pressure of the medium, causing the resistance value of the sensor to change, and checking this with an electronic circuit. Change and convert to output a specification measurement signal corresponding to this pressure.

6. Sapphire Pressure sensor works

Principle of sapphire pressure sensor: Using the strain resistance operation principle, under the effect of pressure, the titanium alloy receiving diaphragm is deformed. After the deformation is sensed by the silicon-sapphire sensitive component, the bridge output will change, and the undulation and change will be changed. The measured pressure is proportional.

The sensor's circuitry ensures power to the strained bridge circuit and converts the strain bridge's unbalanced signal to a consistent electrical signal output (0-5, 4-20mA or 0-5V). In absolute pressure sensors and transmitters, sapphire foils, bonded to ceramic base glass solder, act as elastic elements that convert the measured pressure into strain gauge deformation and then reach the pressure measurement.

7. Piezoelectric pressure sensor works

Working principle: When the inside of the thin cylinder is subjected to the pressure effect, the internal tension of the cylinder increases, and then the natural oscillation frequency is increased. Use this effect. Just measure the natural oscillation frequency of the vibration tube to know the pressure. The measurement accuracy of the natural oscillation frequency of the cylinder is determined by the resonance quality factor Q of the cylinder, the signal processing circuit and the accuracy of the clock signal. It has the characteristics of simple structure, small size, light weight and long service life. Piezoelectric accelerometers have been used extensively in the measurement of oscillations and shocks in aircraft, cars, boats, bridges and buildings, especially in the aerospace and aerospace fields.