What is a Flow Sensor?

A flow sensor is a device that quantifies the flow of fluids, including gases and liquids. These sensors employ both mechanical and electrical systems to detect variations in the fluid's physical properties and determine its flow rate. The measurement techniques vary based on the fluid's characteristics, as gases, liquids, and non-Newtonian fluids exhibit significantly different behaviors, necessitating distinct approaches for accurate flow measurement.

Types of flow sensors

Differential Pressure Flow Sensor

The fluid velocity is directly related to its pressure, as described by Bernoulli's equation:

dp=(density*velocity^2)/2

A differential pressure flow sensor measures the pressure of a fluid by assessing it at two different velocities while keeping the fluid density constant. Typically, these sensors feature a single pressure sensing element, like a Pitot tube, positioned at the edge of the fluid flow path. A change in the nozzle or orifice diameter accelerates the fluid, allowing for pressure measurement at the increased velocity. Once the sensor calculates the pressure difference, Bernoulli’s equation can be applied to determine the fluid velocity. This velocity can then be used to compute the total flow rate through the pipeline.

Accurate velocity calculations necessitate controlling several variables, which is why differential pressure flow sensors often act as "interruptive" components within the pipeline rather than adapting to it. Various types of sensors utilize differential pressure methods, including:

- Venturi tubes

- Rotor flow meters

- Orifice plates

- Pitot tube arrays

These sensors offer different levels of accuracy and system pressure loss. Due to their effectiveness and versatility, differential pressure flow sensors are the most widely used type of flow sensor.