Types of Pressure Measurement:
– Absolute pressure: Referenced against a perfect vacuum.
– Gauge pressure: Referenced against ambient air pressure.
– Differential pressure: Difference between two points.
– Gauge pressure used in closed systems, while differential pressure in industrial processes.
Applications and Reference Types:
– Absolute pressure sensors for high-performance industrial use.
– Gauge pressure sensors for everyday measurements like tire pressure.
– Differential pressure sensors for pressure drops and flow rates.
– Various reference types include vented-gauge, sealed-gauge, and absolute pressure sensors.
Importance of Zero Reference:
– Zero reference clarifies the reference point.
– Absolute pressure sensors provide a constant reference.
– Gauge pressure sensors affected by atmospheric pressure.
– Differential pressure sensors measure differences between points.
Historical Perspective and Static vs. Dynamic Pressure:
– Anaximenes’ observations on pressure and matter.
– Recognition of pressure’s effect on temperature and density.
– Static pressure uniform in all directions, while dynamic pressure is directional.
– Total pressure is the sum of static and dynamic pressures.
Instruments, Units, and Measurement Methods:
– Instruments like pressure gauge, transmitter, and sensors.
– Units include pascal, atmosphere, torr, and pound per square inch.
– Measurement methods like pitot-static tubes for airspeed.
– Various applications in industries requiring accurate pressure measurements for safety and efficiency.
Pressure measurement is the measurement of an applied force by a fluid (liquid or gas) on a surface. Pressure is typically measured in units of force per unit of surface area. Many techniques have been developed for the measurement of pressure and vacuum. Instruments used to measure and display pressure mechanically are called pressure gauges, vacuum gauges or compound gauges (vacuum & pressure). The widely used Bourdon gauge is a mechanical device, which both measures and indicates and is probably the best known type of gauge.
A vacuum gauge is used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (for instance, −1 bar or −760 mmHg equals total vacuum). Most gauges measure pressure relative to atmospheric pressure as the zero point, so this form of reading is simply referred to as "gauge pressure". However, anything greater than total vacuum is technically a form of pressure. For very low pressures, a gauge that uses total vacuum as the zero point reference must be used, giving pressure reading as an absolute pressure.
Other methods of pressure measurement involve sensors that can transmit the pressure reading to a remote indicator or control system (telemetry).
