Summary
Highlights
Flow sensors measure the speed or quantity of liquid or gas moving through a pipe. Flow can be measured by mass (number of molecules), volume (space occupied by fluid), or velocity (speed at which the fluid moves). Each method has specific units, such as kilograms per second for mass, liters per minute for volume, and meters per second for velocity.
Indirect level sensors measure liquid levels using other properties like pressure (pressure sensor), sound waves (ultrasonic sensor), or electrical capacitance (capacitive sensor). These methods infer the liquid level rather than directly measuring it.
Point level sensors detect if a liquid or solid has reached a specific high or low point, acting like a switch. Examples include float sensors and conductive sensors. Continuous level sensors, on the other hand, provide real-time, continuous monitoring of the entire range of liquid levels, showing not just full or empty but the exact quantity, similar to a car's fuel gauge.
The video discusses several point level sensors: float sensors use buoyancy; conductive sensors use electrical conductivity for conductive liquids (not for non-conductive liquids like oil); optical level sensors utilize light refraction to detect liquid presence; and vibrating tuning fork sensors detect changes in vibration frequency when encountering liquid or powder.
Continuous level sensors covered include capacitance level sensors, which measure changes in electrical field due to varying dielectric constants of air and liquid; ultrasonic wave sensors, which use sound waves to measure the distance to the liquid surface contactlessly, similar to sonar; and electromagnetic or radar sensors, which send and receive radio waves to determine liquid levels, even in challenging conditions.
The differential pressure flow meter (DPFM) measures flow rate by detecting pressure differences caused by fluid moving through a restriction in a pipe. It consists of a primary element (like an orifice plate or venturi tube) that creates the pressure difference, a secondary element that measures this difference, and electronic housing to convert the signal into an electrical output.
Primary elements for DPFM include orifice plates (concentric, eccentric, segmental) which are thin plates with holes; Venturi pipes that have a narrow throat section; and flow nozzles, which are simpler and more compact versions of Venturi tubes. These elements create a pressure drop proportional to the flow rate.
Electromagnetic flow meters measure the flow of conductive fluids by inducing voltage in a magnetic field. Ultrasonic flow meters use sound waves to determine fluid velocity without direct contact, employing transit-time or Doppler effect principles.
Turbine flow meters use a rotating rotor whose speed is proportional to fluid flow. Vortex flow meters count vortices shed by a bluff body to measure flow velocity. Positive displacement flow meters directly measure the exact volume of fluid by trapping and releasing fixed volumes with rotating parts like gears or pistons.
Coriolis mass flow meters measure mass flow directly by detecting the twisting effect produced when fluid moves through vibrating tubes, also capable of determining fluid density. Thermal mass flow meters measure the mass flow of gas using internal heaters and temperature sensors, relating heat transfer to flow.