Sealed pressure sensor
A sealed pressure sensor is a type of sensor whose reference pressure cavity is permanently sealed at a fixed pressure during the manufacturing process. It measures the difference between the pressure of the medium being measured and this internally sealed reference pressure.
Important Note: Although it measures a "difference," because its reference pressure is fixed, it essentially still measures an absolute pressure value. It's just that the reference point for this absolute pressure is not zero (vacuum), but a pre-set fixed value.
Core Principle and Structure
Structure:
Unlike vented gauge pressure sensors, sealed pressure sensors do not have a vent port.
Their internal reference cavity is filled with a specific reference pressure (most commonly standard sea-level atmospheric pressure, i.e., 101.325 kPa abs) before the sensor leaves the factory and is then permanently sealed.
One side of the sensing diaphragm is exposed to the pressure being measured, while the other side is exposed to this sealed reference pressure.
Working Principle:
Sensor Output = Absolute Pressure of Measured Medium - Internally Sealed Reference Pressure For example, if a sealed pressure sensor's reference cavity is sealed at 1 standard atmosphere, then:
- When the absolute pressure of the measured medium is exactly 1 standard atmosphere, the sensor output is 0.
- When the measured pressure is higher than 1 standard atmosphere, the output is a positive signal.
- When the measured pressure is lower than 1 standard atmosphere, the output is a negative signal.
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