A sensor gauge is a device that utilizes a sensor to measure a physical parameter and typically displays the measurement. While "sensor gauge" can refer to various types of sensors and displays (like a fuel gauge or temperature gauge), when discussing pressure measurement, a key type is the gauge pressure sensor.
Understanding Gauge Pressure Sensors
A gauge pressure sensor measures pressure relative to the local atmospheric pressure. This means it doesn't measure the absolute pressure but rather the difference between the measured pressure and the pressure exerted by the air surrounding the sensor.
Relative Measurement
Unlike sensors that measure absolute pressure (relative to a perfect vacuum) or differential pressure (the difference between two points), a gauge pressure sensor uses the ambient atmospheric pressure as its zero point.
- Zero Reference: The reading on a gauge pressure sensor is 0 psi (pounds per square inch) or 0 bar when the measured pressure is equal to the surrounding atmospheric pressure.
- Positive Readings: Indicate pressure above atmospheric pressure.
- Negative Readings: Indicate pressure below atmospheric pressure (often referred to as vacuum pressure).
Why Atmospheric Pressure Matters
The reference point for a gauge pressure sensor is the local atmospheric pressure. It's important to note that:
- Atmospheric pressure varies across the globe depending on our altitude. Higher altitudes have lower atmospheric pressure.
- Atmospheric pressure even changes in the weather, with high-pressure systems typically indicating fair weather and low-pressure systems associated with storms.
Because of these variations, a gauge pressure reading for the same actual pressure might differ slightly depending on the sensor's location and the current weather conditions.
Practical Examples
Gauge pressure sensors are widely used in various applications where pressure relative to the surroundings is critical.
- Tire Pressure Gauges: The pressure reading on your car tire gauge is a gauge pressure – it tells you how much pressure is above the current atmospheric pressure.
- Process Control: Monitoring pressure in pipes or vessels in factories.
- Medical Applications: Consider, as an example, the vacuum pumps used during or after surgery. These pumps often need to measure and control pressure relative to the operating room's atmosphere to ensure proper suction.
In summary, while "sensor gauge" can be a broad term, focusing on pressure, a gauge pressure sensor is a specific type that provides measurements relative to the ever-present local atmospheric pressure.
