Proteus Industries Inc.

Choosing a mass flow meter requires a bit of knowledge about what is being measured. Both gas and liquid can be quantified using gauges that compute the flow at kilograms per second or liters per second in relation to the density of the material. Each device is different and you can't use the same meter for both wastewater plant and potable water, for example. But choosing one that's perfect for you will not be as difficult if you follow the tips below.

Make a checklist

What is the material to be measured: is it liquid or gas? If so, what type of liquid or gas are you working with? Is the liquid dirty or clean? Do you want the process the information manually or remotely? What about the temperature conditions of the plant and the material, are they hot or cold? Measuring hot water may need a gauge that will compensate for the change in temperature to get an accurate reading. Make sure you consider in your checklist the following: the liquid viscosity, corrosive and conductive properties, toxicity if applicable, and type of piping. When dealing with gases, make sure you list down if it's wet, corrosive, toxic, combustible, or clean.

There are numerous mass or water flow meters to choose from such as coriolis, differential pressure, energy, magnetic, open channel, optical, massive displacement, thermal, turbine, ultrasonic, variable area and vortex. Each has its own advantages and disadvantages.

Narrowing down prospects

There are so many companies offering these devices but the best manufacturers have the best engineers to help your identity plant specifications through an easy-to-follow guide will help determine the perfect product for your needs. You also want a company with strong local presence with qualified partners in North and South America, Asia, Europe, Africa and the Middle East. This is to minimize the potential shut-down time when the mass flow meters encounter a snag since the manufacturer can immediately send in engineers. Also, the manufacturer should be able to offer you a competitive rate along with technical training of your staff, application assistance or taking care of the repair and maintenance.

Saving on costs

The process of listing down the plant specifications will entail cost, if you consider the number of manpower hours alone. Then you have to find the perfect technology that fits your need. An educated estimate would place the expense somewhere between 30 to 40% of the sales cost.

As the name suggests, liquid flow meters are used for measuring the flow rate of liquids. They are an essential device for numerous industries: from oil and gas plants to chemical and pharmaceutical factories, they are used to measure gas, liquid, or both. Extremely durable, reliable, accurate, and cost-effective meters are now possible due to innovations by companies like Proteus Industries Inc. In response to increased industrial demand and technological progress, more computer-interfaced flow meters are being produced, enabling instantaneous and remote flow measurement monitoring.

Features

Though there are various flow meters integrated with new and advanced features, some are essential. The most basic of these are accuracy in measurements, flow velocity range, installation method, and maintenance requirements, some of which are explained in depth below. Output connectivity options and mechanical restrictions should also be considered.

These fluid characters can significantly influence the performance of flow meters, and therefore should be taken into account to ensure the correct application of the device:

Viscosity

Phase (Single/Double)

Temperature

Pressure

Conductivity

Turbidity

Corrosiveness

Flow Profile (ex: Transitional, Turbulent, Laminar

Below are key, variable features of flow meters important to their application.

Flow Range

Minimum and maximum volumetric or mass flows to determine the flow velocity range of the flow meter. This ability is calculated using the ratio of maximum to minimum flow rates and a Reynolds Number. The ability of the flow meter is commonly denoted as a turndown ratio: using the meter outside this range can negatively affect its performance

Repeatability

The repeatability of the flow meter is based on two techniques.

Metering: The repeatability of a particular flow meter, through metering, is tested when the results of the successive measurements, using that particular meter are approximate, in conditions where the same quantity was measured by the same procedure, by the same person at the same location over a short duration. More precisely, it is the feature of the meter to give approximately close values under certain and constant conditions.

Laboratory Technique: In laboratory test technique, the repeatability of the meter is checked through comparing the difference obtained in successive measurements under some definite conditions, by the same operative using the same device plus same material and test technique.

Accuracy

The accuracy of a flow meter is its skill in determining the nearest approximation of the true value. Once the precise measurements and characteristics of the fluid and pipes to be used are noted, the next step is finding an appropriate flow meter with a high accuracy rate. Percentage of calibrated span (CS), the percentage of actual reading (AR), or percentage of full scale (FS) units are typically used to indicate the accuracy of flow meters. Percent CS and FS signify that the absolute error will increase with a change in the measured flow rate. In contrast, percent AR signifies no change in absolute error with rising and falling flow rates.

K-Factor

The k-factor is the ratio of the number of a meter’s pulses to the corresponding net volume of the fluid flowing through the meter during measurement; in other words, it is the pulses per unit volume, an indication of volumetric output. The received pulses are continuously divided by the k-factor through the electronic device giving various outputs like rate and factor totalization. 1\k is usually termed as meter factor. Though the frequency of the pulses is directly proportional to the turbine rotor rotational rate, effects like temperature and change in pressure can alternate the k-factor of a meter. So, the manufacturer of the meter should be consulted if the K factor varies with changes in liquid form or with changes in the area of the pipe.

Linearity

The dependability of the K factor over a particular flow rate is defined as the linearity of the flow meter. This linearity of the flow meter is usually defined as the band, containing minimum and maximum k-factors as well as a k-mean. The manufacturer normally specifies these lower and upper limits as the maximum and minimum flow range of the particular liquid; these constraints are sometimes defined using temperature and pressure instead.

A broad field of fluid media can be minutely audited and detected with the help of the liquid level indicator switches. The level of the fluid is monitored and restricted for different reasons. The liquid level indicators are also used in measuring the liquid flow. There are different operations of the indicator switches which administer various technologies. They are available in a wide range of non-invasive, contact and non-contact liquid level switches.

Various Types of Liquid Level Switches

The level switch can be distinguished into two categories, solid and liquid. The liquid level switch can be divided into a float level switch, ultrasonic level switch, RF capacitance level switch, and conductivity level switch. A single application can also engage multiple mechanics for the desired result, depending on the consumer choice. Point level detection of fluids and continuous level measurements of liquids are the ways of monitoring the level of the liquid. Point level is the quickest method to detect the level of the liquid, whereas for determining the intermediate levels, the continuous level measurement is recommended.  Point level switch is mandatory for finding the leakage in the pipeline or tank and preventing the overflowing of liquid.

Float Level Switch

To detect the level of water in the tank, the best liquid flow switch is used. It can be used in the pumps, along with the alarm, indicator or other devices. Its complexity varies depending on the demand of the application. The most commonly used float switch is the simple rod that rises as the level of the liquid increases resulting in the operation of the microswitch. They can be conveniently handled and quickly installed. It is a very popular technique in the condensate pumps, sump pumps, power plants, shipbuilding, industrial installation, etc.

Ultrasonic Level Switch

It is used for detecting the level of the bulk slurry. They are the non-contacting liquid level indicator switches. With no mobile parts and low maintenance, it delivers precise and highly satisfactory instant output. These are conventionally used in the chemical manufacturing industry. They are widely accepted for its high flexibility.

RF Capacitance Level Switch

It provides the reliable and precise output in both conducting and non-conducting liquids, irrespective of the open and closed container or channel. The output of this method is not affected by the properties of the materials involved like corrosiveness or conductivity, or by the temperature and pressure. Remote mounted versions are also available and the time delay can also be administered.

Conductivity Level Switch

It detects the level of the conducting fluid of the minimum, maximum, or the intermediate level, that is stored in either open or closed container. This switch can control the liquid between the two fixed levels by regulating the pump operation. It provides the dry running and over spilling protection and is easy to maintain as its calibration free. It is applicable with corrosive liquids and can be operated by remote control.

Liquid Flow Measurement Instruments

Know the Various Types of Liquid Flow Meters

Power generation, processing plants, energy facilities and industrial utilities depend on cost effective management of energy which directly depends upon accurate and reliable flow meter instrumentation. Whether you require precise measurements of air or steam or the flow and density measurement of liquid, an appropriate flow meter must be used.

The role of density in flow measurement

Density is a vital component of fluid property and consequently flow measurement. Density is mass divided into a volume. As a property of the fluid, density depends on the fluid type and the impact of environmental conditions on that particular fluid. For example, oil has a different density than water. Hot water will have a different density than cold water.

Using densitometers, the density of gas and liquid is measured directly.

2. Measurement of fluid components.

For example, when measuring the component of natural gas, a chromatograph can analyze the gas sample and determine amounts of various components within it. Using the density calculations of each component, the density of the entire sample is then obtained.

3. Inference.

The density of the fluid is inferred using measurements of temperature and pressure. This is perhaps the most popular method due to its simplicity. The cost of using temperature and pressure measurements is far less than relying on a chromatograph or densitometer.

The role of Pressure & Temperature on flow and density measurement

Most liquids are non-compressible; therefore, pressure does not have a significant impact on them. As a result, only temperature calculations are necessary to determine density compensation.

In many applications, density constantly changes. This is due to fluctuations in temperature. However fluid composition remains more or less static.

Which flow meters are capable of measuring the flow and density of liquids?

Density affects different flow meters in many ways.

Volume flow meters such as turbine and magnetic meters are not impacted by density fluctuations. The (proportional to flow) signal output (generally pulse (Hz) or analog) from such meters is read out in liters per minute or gallons per minute.

Differential flow meters such as V-Cones and orifice plates depend on density because they are based on Bernoulli’s theorem. This is true irrespective of whether the flow meter is measuring mass or volume flow rates.

Mass flow meters such as best thermal mass flow meter and Coriolis flow meters take direct flow rates. They produce signal outputs (see previous) read out in pounds per minute.

How does a Coriolis flow meter measure density?

Coriolis flow meters make direct mass and density flow measurements based on the Coriolis Effect; “It is the deflection of the moving objects when they are viewed in the reference of the rotating frame”. The Coriolis flow meter works by artificially introducing Coriolis acceleration into the flow stream. The fluid is deflected within. As a result, the forces that are generated lead to slight distortions or twisting of the measuring tube which are directly proportional to mass flow rate. Special sensors pick up on this distortion and convert the output into a signal.

Water Flow Measurement in Remote Locations

The liquid flow measurement instruments are the devices used to evaluate the flow of water or any liquid in a conduit or an open channel. It is also used to calculate the precise amount of liquid present in the pipeline. These devices not only assess or audit the amount and flow of liquid but also are used to detect any wastage due to leakage. This measurement can be accomplished in various ways and in various mediums like pipelines, tunnels, tanks, natural resources, etc. There are various mechanical and technical instruments, which are used to measure the liquid flow, depending on the applications and type of liquid flowing.

 Various Categories of Liquid Flow Meter

The various designs and technical aspects are responsible for the different designs of the flow meters, which have further variations.

 Water Velocity Measurement Meters: – This category consists of Vortex Shedding, Turbine, Swirl, Electromagnetic, Ultrasonic Doppler, Pilot Tubes, and Calorimetric.

 Differential Pressure Flow Meters: – This flow meter has variations of Venturi Tube, Orifice Plate, Flow Tube, Flow Nozzle, and Rotameter.

 Positive Displacement Flow Meter: – This process of liquid measurement includes Nutating Disc, Rotary Vane Meter, Reciprocating Piston Meter, and Oval Gear.

 Open Channel Flow Meter: – This flow meter can be divided into two categories- Weirs and Flumes.

 Mass Flow Meter: – This flow meter consists of Coriolis and Thermal Flow Meter.

 Output of the Measurement of the Liquid Flow

To achieve the precise and effective measurement of the liquid flow, new technologies are being implemented in the form of digital and analog meters, in the output. To attain the desired result, the meters are attached to the flow meter boards and are placed near the conduits. The digital meters have gained tremendous popularity for its ease of use and accuracy and can be used in commercial as well as domestic fields. The digital devices are widely used in the Magnetic and Ultrasonic Flow Meters. To modify the flow of the liquid, the valve of the pipelines can be conjoined to the data. It is possible because the data obtained from the digital meter can be defined accurately.

 Applications of the Liquid Flow Meter

Proteus Industries provides a reliable flow measurement solution to any oil, gas, liquid or steam operation. The quality of our flow meters can truly be seen at gathering facilities where a custody transfer of millions of gallons of products is required for transfer from one place to another on a daily schedule.

An example of this is crude oil. A gathering station pumps up to 10,000 gallons of crude oil every minute. If a flow meter had a measurement error of just 0.02%, it will result in a loss of 68 barrels every day. A single barrel costs $40, so this will translate to a loss of $1 million every year.

Taking steps to ensure that you are getting a reliable flow measurement solution is key to avoiding disastrous mistakes. One of accomplishing this is by taking steps to prevent measurement inaccuracy. This can be achieved by ensuring that instrumentation is calibrated properly before it enters operation.

In today’s market, companies have access to numerous types of measurement devices. Some of these are Rota meters, vortex, ultrasonic and Coriolis flow meters. All these types of flow meters are advanced technologies. However, their benefits can only be gained if they are put to use properly. Most errors in reliable flow measurement solution occur during preoperational phases. This will eventually lead to complications down the road; incurring very high maintenance costs and next-to-no downtime.

Since flow meters are in continuous operation, drifting (a very serious issue) is highly possible. Periodic proving of your flow meter is essential to identify the drift and correct it. A flow meter will calculate volume by producing pulses in relation to the quantity of fluid passing through it. When there are more pulses, it means the volume is higher. This is meter proving and it is a form of calibration that relies on this concept to maintain accuracy by making comparisons between known liquid volumes that traverse the prover to the volume shown by testing flow meter. Data that is obtained during a proving test may be used to calculate corrections. This enables the operator to alter meter readings so that they represent real flow rates.

Routine calibration or meter proving helps to protect against inaccurate measurements occurring from natural mechanical wear and tear, pipe blockages, product build up and changes in the proeprties of the product over time.

Flow switches are mechanical devices used in controlling the flow of air, steam, or liquid. A flow switch operates by conveying a trip motion (relay, reed switch, paddle) to another machine within the system, usually a pump. The trip signal will indicate to the pump to turn on or turn off. It is necessary to provide damage protection and circuit cooling or adjust flow rates that are too high or too low.

Definition of Flow

Flow refers to the velocity or physical movement of gas, steam, or liquid within a pipe that triggers the actuation of the flow switch. When there is no flow present, the velocity either drops or completely stops; in either case, the switch will revert to its original position.

Flow Switch Uses

A liquid flow switch is applicable in chlorination of a swimming pool, hot water heating, air conditioning, liquid transfer systems, fire sprinkler systems, and industrial laser cooling systems.

Water flow switches are implemented in water sprinkler systems. In the case of a fire, for example, a flow switch can trigger an electrical fire alarm device to turn on.

Air flow switches are used to clean room filter systems, exhaust ventilation, and air treatment systems.

Flow switches are used in many other applications, such as:

·         Water treatment systems

·         Additive or blending systems

·         Air supply systems

·         Duct type heating

What are some of the functions of a flow switch?

Flow switches perform precise functions based on set requirements. They are capable of stopping a motor when there is no flow as well as triggering the same motor to run once the flow starts. It can sound an alarm when the flow arrests, and it can turn off the alarm when the flow rate reaches an appropriate level.

Since flow switches play such an integral role in many industries, there are a few important considerations.

Measuring flow rate accurately is crucial. This is inferred by calculating the change in dynamic energy or velocity; the velocity, in turn, is dependent upon the pressure differential that forces the liquid through the conduit or pipe. Since the cross-sectional area of a pipe is constant and known, the velocity is a good indication of the flow rate. Calculating the flow rate must be done as it assists in setting flow switches to a pre-determined close function.

In closing, here are some types of flow switches to consider for your specific use.

Vane-Operated Flow Switch

A vane-operated flow switch relies on fluid pushing against an internal paddle. As the flow drops to preset levels, it triggers an internal magnetic mechanical and coupling switch actuation lever which essentially trips the switch.

Variable Area Flow Switch

This device has an internal piston which activates the switch. The flow enters a port and adds pressure to the magnetic poppet; once this pressure hits the preset level, the switch will turn off.

Ultrasonic (Doppler) Flow Switch

Attached to the outside of a pipe, ultrasonic sensors send signals when it detects a change in the flow.

Before we understand the difference between a flow transmitter and a flow meter, let us know their need. Both these devices are used to measure the flow of liquid or gas. Today, in industrial processes, there is a necessity to regulate the flow of fluid or gas. So, the primary purpose of such devices is for process control. Now that we have that cleared up. What is a flow meter and nozzle? Flow meters and nozzles are devices used to measure the flow of liquid or gas as they pass through pipes. It is a piece of engineering equipment that measures, monitors, and record the flow rate, discharge, or pressure of liquid and gasses. There are various types of flow meters – differential pressure flow meters, positive displacement flow meters, open channel flow meters, and electromagnetic flow meter.

What is a flow transmitter? A flow transmitter is similar to the flow meter with the difference that it has electronics inside the pipe to provide electrical output in voltage or current.

Types of Flow Transmitters

Turbine Flow Transmitter

The turbine flow transmitter is an electronic sensor that indicates the flow of liquid as an electric transmission output. There is a broad application of this device for industrial, laboratory flow applications, and commercial.

For industrial use, the turbine flow transmitter is used in oil & gas (water injection, test and production separators, disposal wells, hydraulic fracturing, chemical injection, and natural gas pipelines), Aerospace/Defense (engine testing, fuel flow measurement, shipboard reverse osmosis systems, and monitor fuel supply to ship engines), pharma bio-tech (sanitary measurement, and pill coating), power generation (custody transfer), industrial & municipal (building automation, HVAC, and water metering), cryogenics (liquid measurement of plant applications and trunk deliveries). Water flow transmitter is also a type of the turbine flow transmitter.

Turbine In-line Flow Transmitters

There are mainly three types of turbine – calorimetric, shuttle, and differential pressure. The turbine in-line flow transmitters are sensors that provide electric output to indicate the flow of liquid remotely. Some of the applications of the transmitter are for process control, pump testing, irrigation, drain lines, and chemical batching.

In-line Electromagnetic Transmitters

This is similar to all the above transmitters in its core working; however, the device uses electromagnetic sensors to generate electrical transmission output of the flow rate of the liquid. There are no moving parts in this transmitters, and the accuracy of measurement is lesser than other transmitters. Electromagnetic flow transmitters are for reversible gauging of the volume flow of conductive liquids in closed piping.

Ultrasonic Flow Transmitters

Ultrasonic flow transmitters are sensors that use ultrasound to transmit electrical output to indicate the flow rate of liquid. Usually, these devices are light, compact, and cost-effective. Some of the applications of the device are treated diesel oil, water, river water, utility billing, flow measurement of heating metering, and data logging.

Paddlewheel Flow Transmitters

Similarly, to all the above transmitters, the paddlewheel also functions alike with the slight difference that it has paddlewheel in the device. It has a variety of applications from HVAC systems to chemical proportioning and more.

In industrial work settings, the accurate measure of flow is highly critical. Not only does this define profit or loss, but consumer and worker safety are at stake as well. Flow meters are vital in the precise and accurate measurement of flow rate (mass or volume), i.e. the amount of fluid that passes through a pipe.

Flow meters are used in a variety of applications. They measure the mass flow rate or volumetric flow rate. The application will depend on the capacity and type of the flow meter. As a result, each type of flow meter will have its own engineering requirements and constraints. A flow meter will often be referred to by its name. Common examples include flow indicator, flow gauge, liquid meter, etc. This depends upon the industry where it is being used; nevertheless, the function will be the same.

There are five essential types of flow meters. Although the list below is by no means exhaustive, it addresses the most well-known types of flow meters used in industries today:

1. Differential Pressure Flow Meters

This type of flow meter relies on Bernoulli’s equation to judge the flow of fluids through a pipe. Differential pressure flow meters present a constriction within the pipe which leads to a drop in pressure across the flow meter. As flow increases, the pressure drop increases. Impulse piping will route the downstream and upstream pressure of the flow meter to a transmitter that will measure the differential pressure to arrive at the fluid flow. Differential flow meters account for up to 21% of the world’s market for flow meters. They are commonly used in industries such as gas and oil, power, chemical, waste, water, mining, metals, paper and pulp, pharmaceutical, beverage, HVAC, and food.

2. Positive Displacement Flow Meters

These are also called mechanical flow meters. They measure the fluid volume, deliver it fast and refill it again. The amount of fluid transferred is calculated. Positive displacement flow meters measure the actual flow of fluid, whereas other flow meters measure other parameters and convert it into a flow rate. In these types of flow meters, the output is correlated to the fluid volume that passes via the flow meter. One can compare a PD flow meter to a stopwatch and a bucket. The stopwatch begins when the flow commences. It stops when the buckets have reached its limit. The flow rate is determined by dividing the volume by time. To obtain a continuous PD measurement, a system is required to continually fill and empty buckets and then divide the flow without letting it exit the pipe. These continually forming and subsiding volumetric displacements are represented by pistons responding in cylinders or gear teeth coupling against the internal wall of the meter.

Examples of positive displacement meters include oval gear meters, piston meters, rotary vane meters, rotating disk meters, etc.

Positive displacement flow meters are highly accurate. They are often used while transferring fluids or oils such as hydraulic fluids, gasoline, water and various gas applications.

3. Velocity Flow Meters

Velocity flow meters determine flow rate by measuring the velocity of a stream to arrive at the volumetric flow rate. These types of flow meters pursue a linear relationship to linear flow rates. Contrary to differential flow meters, no square-root relationship exists in such instruments. Therefore, velocity flow meters have a better range compared to other flow meters. Furthermore, they are less sensitive to alterations in viscosity, provided that Reynolds numbers (Re) of more than 10,000 is used. All velocity type of flow meter housings is fitted with special fittings called flanges. This enables them to be attached directly to pipelines.

The PV6000 series and V7000 series from Proteus Industries Inc. are examples of vortex flow meters. They both rely on the vortex concept to arrive at a reliable, accurate and cost-effective measurement of liquids that require heat transfers. An in-line sensor within the flow meter detects the frequency of the vortices shed by a bluff body within the flow stream. It then creates a pulse output signal which is proportional to flow rate of the fluid; thereby providing a highly accurate measurement.

4. Mass Flow Meters

Also called inertial flow meters, these devices measure the mass flow rate of fluids that travel through a tube. The calculations are mass of fluid traveling pass a static point per time unit. This type of flow meter is used in mass-related processes because they measure force which results from the speeding of mass. Two popular types of mass flow meters include the Coriolis mass meter and the thermal dispersion flow meter.

Coriolis flow meters rely on the Coriolis Effect. This occurs when a mass moves through a rotating system experiencing a special force which acts perpendicular to the motion’s direction and to the axis rotation. Here on earth, this effect deflects moving objects towards the right side in the northern hemispheres and in the southern, to the left. Coriolis flow meters provide a direct measurement of fluid density. These are highly accurate, irrespective of the liquid or gas being measured. The same measurement tube may be utilized for bitumen and hydrogen gas without recalibration. Coriolis flow meters are often used to measure the flow of natural gas. They are also used in industries such as power, mining, pharmaceuticals and waste water.

5. Open Channel Flow Meters

With several kinds of flow switches on the market, it can be difficult to choose the perfect product for your specific purposes. Here are some important things to know before choosing a flow device from a premier manufacturer of flow switches.

What is a Flow Switch?

A flow switch is a mechanical device used to control the flow of liquid, steam, or air. Flow switches do this by sending trip indications to other devices within the framework (such as a pump), signaling it to shut off or turn on and safeguarding it from getting damaged.

This device keeps track of a set point and determines whether the flow is below or above this specific rate. This set point may be fixed or adjustable, depending on the specifications of the product. When this set point is reached, sometimes the response is an electric circuit’s actuation. Once it is tripped, the flow switch remains in its new condition until the flow falls under the set point.

What are the major benefits of Flow Switches?

Flow switches are one of the most trustworthy instrumentations for deciding flow rates. They’re utilized in several industries, such as biomedical and semiconductor manufacturing industries to name just a few. Flow switches are versatile, economically viable instruments providing incredible precision. Some switches can be utilized for actuating visual or audible alarms, as well as other controls and relays.

How are Flow Switches different from Flow Meters?

The main distinction between a flowmeter and a flow switch is the way they perform. Flowmeters simply monitor the flow rates, requiring manual inspection from the operator to determine whether there is any problem. Flow switches, on the other hand, detect the flow and perform a determined action if it reaches the set point, maintaining desired function.

Innovative Products from Proteus Industries

Proteus Industries offers a wide range of flowmeters, flow switches, and other calibration devices used worldwide. Our products are rugged and sensitive, available in several different types of materials, and are suitable for nearly every measuring and monitoring application.

Ultrasonic flow measurement is based on the principle of transmission and receipt of sound waves, which have a unique quality of bouncing off most objects - solid, liquid or gaseous. This technology is vastly different from traditional flow measurement technologies that use turbines or thermal sensors to measure the flow rate of fluids.

Demand from industry for higher accuracy and lower costs have led to development of ultrasonic flow measurement technologies that fulfill meet the requirements of wide range of applications and processes. While there are number of different technologies in ultrasonic measurement currently available in the market, these can broadly be categorized into four types. This categorization is based on the principle on which these technologies are based.

Transit-time Technology

This the original ultrasonic technology developed for measurement of flow rate of fluids. The technology uses the transit time of sound waves to measure velocity. An ultrasonic flow meter based on this technology has two ultrasonic transducers. These transducers act as both transmitters and receivers of ultrasonic sound waves. To measure the flow rate or velocity of fluid - either gas or liquid through the pipe, the flow meter alternates between sending and receiving bursts of ultrasonic sound waves through the transducers. The time taken by the sound waves to travel from the transmitting transducer to the receiving one gives an exact reading of the velocity of liquid in the pipe.

Ultrasonic Doppler Technology

This technology also works by using two ultrasonic sound transducers. However, unlike the transit-time technology, Doppler utilizes one transducer as a continuous transmitter of ultrasonic sound waves. The other transducer acts as a continuous receiver. Sound waves introduced into the flow are reflected or scattered back off suspended particles or bubbles in the fluid and captured by the receiving transducer.

The reflection causes a frequency shift in the sound waves, which is known as the Doppler Effect. By measuring this frequency shift it is possible to determine the flow velocity of the fluid in the pipe. This velocity, when computed with the cross-section area of the pipe gives the flow rate of pipe flow.

Cross-correlation Measurement Technology

Cross-correlation measurement technology works on the principle that turbulent flow of a fluid is formed of eddies that have nearly consistent characteristics across a small cross-section of flow. This is known as the correlation length. A flow meter based on cross-correlation measurement technology has two ultrasonic sensors placed along the direction of flow of fluid.

The first or upstream sensor picks up the signature of turbulence L/V seconds before the second or downstream sensor, where L is the distance between the two sensors and V is the velocity of flow of fluid. The velocity thus turns out to be L/T, where T is the time delay in detection between the two sensors.

Acoustic Doppler Velocity Profiling Technology

The acoustic Doppler Velocity Profiling technology works on the same principle as the Doppler technology, with the difference that it uses three transducers instead of two. One of the transducers is a narrow-beam transducer while the other two are large angle ones. The three transducers are arranged in a straight line with the narrow angle one positioned directly above the flow while the other two ones are placed on either side of it.

The middle transducer emits ultrasonic sound waves at a fixed Pulse Repetition Frequency (PRF), which get scattered from particles within the fluid. The other two transducers receive these reflected waves and provide a "pulse-to-pulse" algorithm. This in turn allows the measurement of the Doppler shift in two different directions, which can be used to create a 2D velocity profile.