Sensor Selection Instructions
1. Type of pressure to be measured
Before ordering pressure sensors or pressure transmitters, users must clarify the type of pressure to be measured. Pressure sensors and transmitters are generally categorized into gauge pressure sensors, absolute pressure sensors and differential pressure sensors. A gauge pressure sensor takes local atmospheric pressure as its zero reference point. An absolute pressure sensor uses vacuum as the zero reference. A differential pressure sensor measures the difference between two pressure values; sensors equipped with two pressure ports that we commonly see all belong to differential pressure sensors.
2. Required Accuracy Grade of the Sensor
This parameter determines the measurement precision of the ordered sensor and serves as one of its key indicators. It is optimal to select a sensor that just meets your basic application requirements. While higher measurement accuracy is desirable, accuracy is directly proportional to price.
3. Measuring Range
This parameter refers to the maximum measurable pressure of a pressure sensor. After confirming the actual working pressure, you should select a sensor with a moderately larger measuring range, generally 1/3 higher than the maximum measured pressure. This prevents unexpected overload that may damage the sensor. For example, if the measured pressure is 100 kPa, a pressure sensor with a range of 150 kPa is recommended.
4. Output Signal
Pressure sensors are available with different output signals for various applications. Standard versions include millivolt (mV) raw signals and conditioned standard signals (for pressure transmitters). The most common types are 4–20 mA and 0–10 V, known as current output and voltage output respectively. Cangzheng pressure transmitters support both voltage and current outputs, which customers can choose according to their actual needs.
5. Operating Environment Requirements
Sensors operate under diverse working conditions. Some may be installed in highly humid locations; others work outdoors exposed to wind and rain for long periods. Strong electromagnetic interference may also exist around the installation site. Customers must communicate all such conditions with the manufacturer and clearly state them when placing orders.
6. Temperature of Measured Medium
The temperature of the process medium greatly impacts the temperature coefficient requirements of the sensor. Improper selection will severely reduce the measurement accuracy and service life of the pressure sensor. Take diffused silicon pressure sensors as an example: their compensated temperature range is normally -10℃ to 60℃, within which the sensor can maintain guaranteed measurement accuracy. If the medium temperature falls between -10℃~40℃ or 60℃~80℃, the sensor can only remain intact without guaranteed precision. If the medium temperature exceeds 80℃, customers shall contact the manufacturer for special customized processing or order high-temperature resistant pressure sensors.
7. Corrosiveness of Measured Medium
Customers must fully understand the properties of the medium to be measured before ordering sensors. If the medium is corrosive, notify the manufacturer in advance and specify this requirement. Otherwise, the service life of the sensor will be drastically shortened, causing troubles and economic losses for both parties.
8. Pressure Connection Size
Customers shall provide the required pressure connection size for Cangzheng pressure sensors and transmitters according to their equipment assembly demands. Standard common thread sizes include M20×1.5 and M12×1, and custom connections are available upon request.
9. Properties of Measured Medium
This factor is often overlooked by many customers and manufacturers. Sensors used for media with special properties require targeted structural design. For instance, kerosene is a highly permeable fluid. Corresponding sealing and packaging measures must be adopted for pressure sensors and transmitters measuring kerosene, otherwise the service life of the products will be shortened.
Introduction to Pressure Sensors
1. Composition
A pressure sensor consists of three parts:
Sensing Element：
A component that directly detects the measured pressure and outputs another physical quantity correlated with pressure, also known as an elastic body, such as springs, beams, bellows, diaphragms and so on.
Transduction Element：
It converts the output signal from the sensing element into an electrical signal available for subsequent processing, including strain gauges, piezoelectric crystals, capacitors, etc.
Signal Conditioning Circuit：
It amplifies and filters the signals output by the transduction element for post-processing.
2.Classification
Pressure sensors can be classified into strain gauge, piezoresistive, capacitive, piezoelectric, resonant frequency, photoelectric, optical fiber and ultrasonic types according to different sensing and transduction elements. The four most commonly used types are as follows:
Strain Gauge Pressure Sensor
Strain gauge pressure sensors measure pressure by detecting strain generated on elastic components. Strain elements are divided into metal and semiconductor types based on manufacturing materials. The resistance of conductors and semiconductors will change when mechanical deformation occurs.
Piezoresistive Pressure Sensor
Piezoresistive pressure sensors are manufactured utilizing the piezoresistive effect of monocrystalline silicon and integrated circuit technology. When force is applied to monocrystalline silicon, its resistivity changes. A measuring circuit then outputs an electrical signal proportional to the applied force. Unlike bonded strain gauges, this sensor relies on a silicon diaphragm to sense the measured pressure.
Capacitive Pressure Sensor
Capacitive pressure sensors convert measured pressure into capacitance variation. Circular metal foils or metal-coated films are used as capacitor electrodes. When pressure deforms the film, the capacitance value changes to generate an electrical signal.
Piezoelectric Pressure Sensor
Piezoelectric pressure sensors leverage the piezoelectric effect. They convert pressure into electrical quantities via electrical components and mechanical structures for subsequent measurement.
3.Installation Method
· Mounting Methods: Threaded Mounting, Flush Surface Mounting, Accessory Mounting
· Mounting Space: Dimension Requirements of the Sensor
4.Loading Mode & Force Types
· Loading Forms: Point, Surface, Bore Load
· Measurable Forces: Compression, Tension, Torque
5. Operating Environment Requirements
· Temp. & Humidity
· IP Rating
· Explosion-proof Class
