Ceramic Capacitive Absolute Pressure Sensor

A ceramic capacitive absolute pressure sensor is a type of sensor that uses alumina ceramic as its core material and measures pressure relative to an absolute vacuum reference point by detecting changes in capacitance.

 

Simply put, it is a"variable capacitor" that directly converts pressure into a change in capacitance, with its reference cavity being hermetically sealed under vacuum.

Its core component is a ceramic capacitive sensing core, typically manufactured using multi-layer co-firing technology:

Structure: It consists of a ceramic substrate with a fixed electrodeand a ceramic thin film (diaphragm) that acts as the movable electrode, bonded together at high temperatures using glass frit.

After bonding, an extremely small, hermetically sealed vacuum reference cavity is formed between them. This is the key to achieving absolute pressure measurement.

This structure forms a parallel-plate capacitor:

• Plate 1: The fixed lower electrode (printed on the ceramic substrate).
• Plate 2: The movable upper electrode (the ceramic diaphragm itself, usually metallized).
• Dielectric: Vacuum (inside the reference cavity) and ceramic.

• Initial State: Under absolute vacuum, the ceramic diaphragm is undeformed, and the capacitance value is an initial value, C₀.
• Applied Pressure: When external pressure (absolute pressure) acts on the outer side of the ceramic diaphragm, the diaphragm undergoes a slight bending deformation towards the vacuum reference cavity.
• Capacitance Change: This deformation causes the distance between the two capacitor plates to decrease.
  According to the parallel-plate capacitor formula C = εA/d(where ε is the permittivity and A is the relative plate area), a decrease in distance results in an increase in capacitance value C.

• Signal Measurement: A subsequent dedicated circuit (typically an ASIC - Application-Specific Integrated Circuit) detects this minute change in capacitance, converts, amplifies, and linearizes it, and finally outputs a standardized signal (such as voltage or a digital signal) proportional to the absolute pressure.

Hot Tags: ceramic capacitive absolute pressure sensor, China ceramic capacitive absolute pressure sensor suppliers