Ultrasonic flow meters

The ultrasonic flowmeter comes with two transducers that are placed on the exterior of the pipe. There is an ultrasonic wave that is transmitted from the first transducer until it crosses the pipe and received by the second transducer. When a flow exists, the sound moves faster upstream then it does downstream. The difference in the upstream and downstream measurements taken over the same flow path will give you the flow rate.

Accurate flow rate measurement is dependent on the signal moving across the pipe to be received by the sensor, so the liquid cannot maintain a large amount of bubbles or objects. In addition, the distance apart between the transducers is also imperative. Therefore, LORRIC has designed a patented guide rail for transducers， that help maintain accurate flow measurement.

Variable area flow meters

 

The methodology behind the variable area flowmeter is the balance effect created by the force of the fluid pushing up and gravity pulling down the float. Because of the see through body users can read the flow rate using the float. An increased volumetric flow rate through an area increases flow speed and drag force, so the float will be pushed upwards. However, as the inside of the VA-flowmeter is cone shaped so it widens, the area around the float increases, the flow speed and drag force decrease until there is an equilibrium with the float’s weight.

 

→See LORRIC’s variable area flow meter

 

 

Coriolis flow meters

The basic operation of Coriolis flow meters is based on the principles of motion mechanics. As fluid moves through a vibrating tube it is forced to accelerate as it moves toward the point of peak-amplitude vibration. Conversely, decelerating fluid moves away from the point of peak amplitude as it exits the tube. The result is a twisting reaction of the flow tube during flowing conditions as it traverses each vibration cycle.

Paddle wheel flow meter

Paddlewheel flow meters have three parts: the paddlewheel sensor, pipe fitting and the operational display device. The paddlewheel sensor consists of a rotating mechanical wheel and impeller with embedded magnets which are positioned perpendicular to the flow and rotate with the moving flow. As the blades spin, the paddlewheel generates a frequency and voltage which is proportional to the flow rate. The faster the flow the higher the frequency and voltage output.

The paddlewheel meter is designed to be either inline (pipe fitting) or insertion. These are available with a wide range of fittings styles, connection methods and materials such as PVC, PVDF and stainless steel. Similar to turbine meters, the paddle wheel meter requires a minimum run of a straight pipe before and after the sensor.

Paddle Wheel flow meters finish the job. It is easy to install and operate, which results in a very low overall cost. Also, it offers high accuracy (.5% full scale) on system applications like water dispensing, water lines, RO and chemical feeding. Paddlewheel flowmeters are evidence that a high price tag doesn’t alway mean better value.

The way to calculate flow rate by paddle wheel flow meters: Flow rate per pulse x Numbers of pulse ÷ Time = Instantaneous flow               

Positive displacement flowmeter

  

A positive displacement meter is a type of flow meter that requires fluid to mechanically displace components in the meter in order for flow measurement. Positive displacement (PD) flow meters measure the volumetric flow rate of a moving fluid or gas by dividing the media into fixed, metered volumes (finite increments or volumes of the fluid). A basic analogy would be holding a bucket below a tap, filling it to a set level, then quickly replacing it with another bucket and timing the rate at which the buckets are filled (or the total number of buckets for the “totalized” flow). With appropriate pressure and temperature compensation, the mass flow rate can be accurately determined. (Citing source: Wikipedia)

Karman vortex flow meter

Vortex flowmeter is a flow meter for measuring fluid flow rates in an enclosed conduit.

When the medium flows through the Bluff body at a certain speed, an alternately arranged vortex belt is generated behind the sides of the Bluff body, called the "von Kármán vortex". Since both sides of the vortex generator alternately generate the vortex, the pressure pulsation is generated on both sides of the generator, which makes the detector produce alternating stress. The piezoelectric element encapsulated in the detection probe body generates an alternating charge signal with the same frequency as the vortex, under the action of alternating stress. The frequency of these pulses is directly proportional to flow rate. The signal is sent to the intelligent flow totalizer to be processed after being amplified by the pre-amplifier. (Citing source: Wikipedia)

Turbine flow meter

Turbine meters are simple to operate and maintain, and in service worldwide as a reliable, cost-effective method for achieving accurate flow measurement. Turbine flow meters are designed to maximize throughout and minimize pressure drop, maintain high flow rates over an extended flow range and offer pulse output that is linear to the flow rate. The turbine meters also minimize fiscal measurement uncertainty by delivering high-frequency pulse resolution to account for minute increments of the flow rate.

Differential pressure flowmeters

  

Differential pressure flowmeters use Bernoulli’s equation to measure the flow of fluid in a pipe. Differential pressure flowmeters introduce a constriction in the pipe that creates a pressure drop across the flowmeter. When the flow increases, more pressure drop is created. Impulse piping routes the upstream and downstream pressures of the flowmeter to the transmitter that measures the differential pressure to determine the fluid flow.

Laminar flow element flow meter

  

Laminar flow elements measure the volumetric flow of gases directly. They operate on the principle that, given laminar flow, the pressure difference across a pipe is linear to the flow rate. Laminar flow conditions are present in a gas when the Reynolds number of the gas is below the critical figure. The viscosity of the fluid must be compensated for in the result. Laminar flow elements are usually constructed from a large number of parallel pipes to achieve the required flow rating. (Citing source: Wikipedia)

Electromagnetic flow meter

A magnetic flow meter (mag meter, electromagnetic flow meter) is a transducer that measures fluid flow by the voltage induced across the liquid by its flow through a magnetic field. A magnetic field is applied to the metering tube, which results in a potential difference proportional to the flow velocity perpendicular to the flux lines. The physical principle at work is electromagnetic induction. The magnetic flow meter requires a conducting fluid, for example, water that contains ions, and an electrical insulating pipe surface, for example, a rubber-lined steel tube. If the magnetic field direction were constant, electrochemical and other effects at the electrodes would make the potential difference difficult to distinguish from the fluid flow induced potential difference. To mitigate this in modern magnetic flowmeters, the magnetic field is constantly reversed, cancelling out the electrochemical potential difference, which does not change direction with the magnetic field. This however prevents the use of permanent magnets for magnetic flowmeters. (Citing source: Wikipedia)

Thermal mass flow meter

The method of this flow measurement is to replace two pipes (or other objects which could be heated), and heat one of them. When fluid flows by a heated pipe, the heat will be taken away by fluid. The temperature of fluid will get higher. Through the temperature difference of both pipes, flow rate could be measured. This flow measurement theory needs more time to reach stable status.