Pressure is defined as force per unit area that a fluid exerts on its surroundings.The SI unit for pressure is Pascal (N/m²), but other units such as psi, atmospheres or bars are also common.
There are three methods for measuring pressure; Absolute, Gauge and Differential. Absolute pressure is referencing vacuum, while gauge and differential pressure are relative to another pressure such as ambient atmospheric or the pressure somewhere else in the system.
Common applications for pressure metering with the ezeio are:
- HVAC systems – monitoring differential pressure in ducts and ventilated spaces.
- Pump systems – keeping track of performance and alerting for blockage or failing equipment.
- Tank level monitoring – monitoring fluid levels and warning for under/overflow.
Most pressure sensors with electrical interfaces will provide a current, voltage or resistance that is relative to the measured pressure. Selecting the correct sensor will depend on the type of media (fluid/gas), pressure levels and physical form factor.
The absolute measurement method is relative to 0 (zero) Pa, or vacuum. The measured pressure is the sum of the atmospheric pressure and the measured pressure. Absolute pressure measurement is usually used for measuring atmospheric pressure in altimeters, meteorological equipment or vacuum chambers.
Gauge pressure is the differential between the surrounding air pressure and the measured media. Since the atmospheric pressure will act on the measured media, the Gauge pressure excludes external factors. Gauge pressure can be described as Differential pressure in the special case where one side is the atmosphere.
Gauge pressure is often used to measure pressure in sealed spaces, such as tires, tanks or pipes.
Differential pressure measures the difference between two sensors. Atmospheric pressure is not a factor since it should apply the same on both sensors. Differential pressure is often used in HVAC systems to monitor performance and leakage. For example the difference in pressure on two sides of a fan will indicate how the fan is operating and if the airflow is unobstructed.