I. Working Principle of Pressure Sensor
A pressure sensor is a device or apparatus that can sense pressure signals and convert them into usable electrical signals according to a certain rule.
Pressure sensors typically consist of a pressure-sensitive element and a signal processing unit. Based on different test pressure types, pressure sensors can be classified into gauge pressure sensors, differential pressure sensors, and absolute pressure sensors.
Pressure sensors are one of the most commonly used sensors in industrial practice. They are widely used in various industrial automation environments, including water conservancy and hydropower, railway transportation, intelligent buildings, production automation, aerospace, military, petrochemical, oil wells, power, shipbuilding, machine tools, pipelines and many other industries.
1. Strain gauge pressure sensor principle
The core component of a resistance strain gauge pressure sensor is the resistance strain gauge. When the metal wire is subjected to external force, its length and cross-sectional area change, and it is easy to see from the above formula that its resistance value will change accordingly. When the metal wire is compressed by external force, its length decreases and its cross-sectional area increases, and the resistance value will decrease.
2. Principle of Ceramic Pressure Sensor
The corrosion-resistant ceramic pressure sensor does not transmit liquid; the pressure acts directly on the front surface of the ceramic diaphragm, causing the diaphragm to undergo slight deformation. Thick-film resistors are printed on the back of the ceramic diaphragm and connected to form a Wheatstone bridge. Due to the piezoresistive effect of the piezoresistor, the bridge generates a highly linear voltage signal that is proportional to the pressure and also proportional to the excitation voltage.
3. Principle of Diffused Silicon Pressure Sensor
The pressure of the medium acts directly on the diaphragm of the sensor, causing the diaphragm to produce a micro-displacement proportional to the medium pressure. This causes a change in the resistance value of the sensor, which is detected by electronic circuitry and converted into a standard measurement signal corresponding to this pressure.
4. Sapphire pressure sensor principle
Utilizing the working principle of strain gauge resistance, the titanium alloy receiving diaphragm deforms under pressure. This deformation is sensed by the silicon-sapphire sensing element, and its bridge output changes accordingly. The magnitude of the change is proportional to the measured pressure.
5. Principle of piezoelectric pressure sensor
When a thin cylinder is subjected to pressure on its inner side, the internal tension of the cylinder increases, thereby raising its natural vibration frequency. The accuracy of measuring the natural vibration frequency of the cylinder depends on the cylinder's resonant quality factor Q, the signal processing circuit, and the accuracy of the clock signal.
II. How to maintain a pressure sensor
Pressure sensors are widely used in many environments. While we may know how to select and use pressure sensors, do we know how to maintain them? What are some methods for routine pressure sensor maintenance?
Pressure sensor manufacturers typically offer a one-year warranty, some even two years. However, no manufacturer will regularly maintain your pressure sensor, so it's essential to understand the routine maintenance methods. Here are eight key points:
1. Prevent slag from depositing inside the conduit and prevent the sensor from coming into contact with corrosive or overheated media.
2. When measuring gas pressure, the pressure tap should be located at the top of the process pipeline, and the sensor should also be installed at the top of the process pipeline so that accumulated liquid can be easily injected into the process pipeline.
3. When measuring liquid pressure, the pressure tap should be located on the side of the process pipeline to avoid sediment buildup.
4. The pressure-conducting pipe should be installed in a location with minimal temperature fluctuations.
5. When measuring liquid pressure, the sensor should be installed in a location that avoids liquid impact (water hammer phenomenon) to prevent damage to the sensor due to overpressure.
6. When freezing occurs in winter, outdoor sensors must be protected against freezing to prevent the liquid in the pressure inlet from expanding due to freezing, which could lead to sensor damage.
7. When wiring, pass the cable through the waterproof connector or flexible conduit and tighten the sealing nut to prevent rainwater or other substances from seeping into the transmitter housing through the cable.
8. When measuring steam or other high-temperature media, a condenser such as a buffer tube (coil) should be connected to prevent the sensor's operating temperature from exceeding its limit.
Understanding the above-mentioned routine maintenance methods for pressure sensors is very helpful, ensuring that our pressure sensors last longer and perform more stably. Of course, these are just a few points for routine maintenance; there are other things to note, such as sending the sensor back to the manufacturer for calibration after one year of use to prevent sensor misalignment.
