Working Principle and Maintenance of Pressure Transmitters

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Working principle and characteristics of pressure sensors (transmitters): Piezoresistive transmitters use piezoresistive sensing elements; they are compact in size, highly sensitive, and exhibit good stability. Their key characteristics lie in these sensing elements. As the name implies, the principle of a piezoresistive transmitter is that a change in pressure acts on the sensitive core, causing a change in resistance; this resistance change is then converted into a standard signal through an amplification circuit. Currently, there are three common types of piezoresistive cores based on different principles:
**Strain principle:** The piezoresistor is combined with a strain material (usually stainless steel) in the form of a Wheatstone bridge. **Features:** High overload capacity and impact resistance; lower sensitivity. Suitable for measuring high pressure levels above 500 kPa, with a maximum range of up to 500 MPa. It has high strength, is resistant to vibration, and is not prone to damage. It exhibits minimal temperature drift, and maintains good linearity over high pressure ranges (above 1 MPa), offering high precision. Its rigid diaphragm structure makes it suitable for measuring various media that are compatible with the strain material.

**Ceramic piezoresistive principle:** The piezoresistor is integrated with ceramic material in the form of a Wheatstone bridge. **Features:** Lower overload capacity compared to the strain principle, as well as poorer impact resistance. It has higher sensitivity and is suitable for measuring high pressure levels above 50 kPa, with a maximum range of 40 MPa. It is corrosion-resistant and can operate over a wide temperature range.

**Diffused silicon principle:** In this case, particles are implanted into silicon wafers to create piezoresistors in the form of a Wheatstone bridge. Features: High sensitivity and high precision; suitable for measuring pressures in the range of 1 kPa to 40 MPa. It has a strong overpressure resistance and good impact pressure tolerance. However, it experiences significant temperature drift. There are two types: those with an isolated diaphragm and those without. Diaphragms without isolation can only be used for measuring clean gases, while those with isolation are flexible diaphragms that are not suitable for measuring viscous media. Generally speaking, piezoresistive transmitters are characterized by their compact size, good accuracy and stability. Temperature drift can be reduced to a minimal level through circuit compensation (or built-in sensor compensation). The main drawback is that their pressure overload capacity is typically only three times the full scale, which makes it inconvenient for range adjustments; generally, the range of such transmitters needs to be