Industrial Sensors: Pressure, Level, Flow, & Motion

Pressure Sensor Definition

A device measuring gas or liquid pressure, and indirectly flow, speed, water level, and altitude.

Alternative Names for Pressure Sensors

Transducers, transmitters, senders, indicators, piezometers, and manometers.

Pressure (P) Formula

Force per unit area (P = Force / Area).

Hydrostatic Pressure Calculation

Height multiplied by density (Head pressure).

Gas Behavior Regarding Pressure

Pressure increases proportionally with temperature; compression reduces space between gas molecules.

Nonelectrical Pressure Instruments

Liquid column gauges, Bourdon tube gauges, diaphragm gauges, and bellows gauges.

Electronic Pressure Instruments

Semiconductor and transverse strain gauges, piezoelectric crystals, capacitive detectors, piezoresistive sensors, and Pirani vacuum sensors.

Level Sensor Function

Specialized displacement sensors used to measure solid or liquid levels.

Mechanical Level Detection

Float systems that ride up and down with liquid level changes.

Optical Level Sensors

Uses infrared light; refraction changes trigger detection when liquid touches the sensor tip.

Vibrating (Tuning Fork) Level Sensors

A vibrating fork changes frequency when immersed; ideal for powders, granules, and viscous liquids.

Ultrasonic Flow Sensors

Uses high-frequency sound waves via Transit-Time or Doppler Shift; non-invasive for large pipes.

Vortex Flow Sensors

Uses a bluff body to create vortices where shedding frequency is proportional to flow rate.

Flow Sensor Selection Criteria

Fluid type, flow range, pipe size, environmental conditions, and output type.

Motion Sensors

Designed to measure the rate of change of position, location, or displacement of an object.

Strain Sensors

Secondary components used to measure process variables like flow, pressure, weight, and acceleration.