Types of Pressure Measurements

Pressure measurement can either be relative to a reference value or on an absolute scale.
1. Absolute Pressure Measurement: Pressure measured relative to perfect vacuum is termed
as absolute pressure. Perfect vacuum is a condition where there is no matter present in the atmosphere and hence, nil air pressure exists in that region. Absolute pressure sensors have limited usage because it is impossible to attain a state of perfect vacuum. Hence, sensors based on absolute pressure measurement require strict specifications for precise outputs. Sensors based on this type of measurement are used in barometric or altitude related pressure measurements.
2. Differential Pressure Measurement: In differential pressure measurement, pressures of two distinct positions are compared. For example, pressure difference calculated by measuring it at different floors of a tall building will give us differential pressure. Differential pressure measurements, typically taken in pound per square inch differential (psid), are applied when high amount of pressure is to be measured. These types of measurements are used for feed pressure monitoring purposes where the pressure with which the fluid is flowing in a medium is monitored, so that homogeneity in the flow can be maintained.
Differential pressure measurements find an important application in monitoring filters in various types of purification systems. They take the reference of the normal pressure with which the filters clean the fluid. Whenever the filters face the problem of clogging due to contaminants, these pressure sensors give a reading relative to the normal pressure. This helps in keeping the filter clean and operational.
3. Gauge Pressure Measurement: It can be defined as a subtype of differential pressure measurement where we compare pressure at any point to the current atmospheric pressure. Gauge pressure measurement is used in applications like tire pressure or blood pressure measurement. There is no consistency in gauge pressure measurements because atmospheric pressure does vary with altitude and hence its applications are limited to non-critical measurements.

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