Water meter - AbsoluteAstronomy.com

A water meter is a device used to measure the volume of water usage. This article provides an overview of technical aspects of water meters. The worldwide prevalence of metering as well as its economic benefits and costs are covered in the separate article on water metering

Water metering

Water metering is the process of measuring water use through water meters.- Prevalence :Water metering is common for residential and commercial drinking water supply in many countries, as well as for industrial self-supply with water. However, it is less common in irrigated agriculture, which is...

.

In many developed countries water meters are used at each residential and commercial building in a public water supply system. Water meters can also be used at the water source, well, or throughout a water system to determine flow through that portion of the system. Water meters typically measure and display total usage in cubic feet

Cubic foot

The cubic foot is an Imperial and US customary unit of volume, used in the United States and the United Kingdom. It is defined as the volume of a cube with sides of one foot in length.-Conversions:- Symbols :...

(ft.³), cubic meter

Cubic metre

The cubic metre is the SI derived unit of volume. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère...

s (m³) or US gallons on a mechanical or electronic register. Some electronic meter registers can display rate-of-flow as well as total usage.

There are several types of water meter in common use. Selection is based on different flow measurement methods, the type of end user, the required flow rates, and accuracy requirements.

In North America, standards for manufacturing of water meters are made by the American Water Works Association

American Water Works Association

American Water Works Association was established as an international non-profit professional organization dedicated to the improvement of water quality and supply. Founded in 1881, it claims a membership of around 56,000 members worldwide as of 2010.AWWA has become the largest organization of...

Types of meters

There are two major methods of flow measurement in use, displacement and velocity, with sub-technologies within each of them. Common displacement designs include oscillating piston and nutating disk meters. Velocity-based designs include single- and multi-jet meters and turbine meters. There are also non-mechanical designs, for example electromagnetic and ultrasonic meters.

In addition to the more common types of meter, there are meters designed for special uses. Most meters in a typical water distribution system

Water supply network

A water supply system or water supply network is a system of engineered hydrologic and hydraulic components which provide water supply. A water supply system typically includes:# A drainage basin ;...

are designed for cold potable water only. There are specialty water meters manufactured for specific other uses. Hot water meters are designed with special materials that can withstand higher temperatures. Meters for reclaimed water

Reclaimed water

Reclaimed water or recycled water, is former wastewater that is treated to remove solids and certain impurities, and used in sustainable landscaping irrigation or to recharge groundwater aquifers...

have special lavender register covers to signify that the water is non-potable and should not be used for drinking.

Water meters are generally owned, read, and maintained by a public water provider such as a city, rural water association, or private water company. In some cases an owner of a mobile home park, apartment complex or commercial building may be billed by a utility on one meter, and want to share the cost of the bill among the tenants. In this case, private meters may be purchased to separately track usage of each unit in what is called submetering

Utility submeter

Utility Submetering is the implementation of a system that allows a landlord, property management firm, condominium association, homeowners association, or other multi-tenant property to bill tenants for individual measured utility usage...

Displacement water meters

This type of water meter is most often used in residential and small commercial applications. Displacement meters

Displacement Volumetric Meter

A Displacement Volumetric Meter is a device which measures total volume. It can operate on the principle of the fluid sweeping out a fixed calibrated volume, which produces a rotation of a calibrated gauge. By maintaining constant conditions and taking readings over a prescribed period the flow...

are commonly referred to as Positive Displacement

Positive displacement meter

A positive displacement meter is a type of flow meter that requires the fluid being measured to mechanically displace components in the meter in order for any fluid flow to occur. Positive displacement flowmeters make volumetric flow measurements taking finite increments or volumes of the fluid...

, or "PD" meters. Two common methods of positive displacement measuring are Oscillating Piston meters and Nutating Disk meters. Either method relies on the water to physically displace the moving measuring element in direct relation to the amount of water that passes through the meter. The piston or disk moves a magnet that drives the register.

PD meters are generally very accurate at low to moderate flow rates typical of residential and small commercial users, and are common in sizes from 5/8" to 2". Because displacement meters rely on all water flowing through the meter to "push" the measuring element, they generally are not practical in large commercial applications requiring high flow rates or low pressure loss. PD meters normally have a built-in strainer to protect the measuring element from rocks or other debris that could stop or break the measuring element. PD meters normally have bronze, brass or plastic bodies with internal measuring chambers made from molded plastics and stainless steel.

Velocity water meters

A velocity-type meter measures the velocity of flow through a meter of a known internal capacity. The speed of the flow can then be converted into volume of flow for usage. There are several types of meters that measure water flow velocity to determine totality usage. They include jet meters (single-jet and multi-jet), turbine meters, propeller meters, and mag meters. Most velocity-based meters have an adjustment vane for calibration of the meter to required accuracy.

Multi-jet meters

Multi-jet meters are very accurate in small sizes and are commonly used in 5/8" to 2" sizes for residential and smaller commercial uses. Multi-jet meters use multiple ports surrounding an internal chamber, to create multiple jets of water against an impeller. The impeller

Impeller

An impeller is a rotor inside a tube or conduit used to increase the pressure and flow of a fluid.- Impellers in pumps :...

rotation speed is in relation to the velocity of water flow. Multi-jets are very accurate at low flow rates, but are not used in larger sizes, since they don't have the straight-through flow path needed for the high flow rates used in large pipe diameters. Multi-jet meters generally have an internal strainer element that can protect the jet ports from getting clogged. Multi-jet meters normally have bronze

Bronze

Bronze is a metal alloy consisting primarily of copper, usually with tin as the main additive. It is hard and brittle, and it was particularly significant in antiquity, so much so that the Bronze Age was named after the metal...

alloy bodies or outer casings, with internal measuring parts made from modern thermoplastics and stainless steel.

Turbine meters

Turbine meters are less accurate than displacement and jet meters at low flow rates, but the measuring element does not occupy or severely restrict the entire path of flow. The flow direction is generally straight through the meter, allowing for higher flow rates and less pressure loss than displacement-type meters. They are the meter of choice for large commercial users, fire protection, and as master meters for the water distribution system. Strainers

Strainers

Water lines or kitchen systems can get gravel, deposits that break free, and other stray items in the line. The velocity of the water pushing them, they can severely damage or clog devices installed in the flow stream of the water line. A strainer is essentially a screen installed to allow liquids...

are generally required to be installed in front of the meter to protect the measuring element from gravel or other debris that could enter the water distribution system. Turbine meters are generally available for 1-1/2" to 12" or higher pipe sizes. Turbine meter bodies are commonly made of bronze, cast Iron

Cast iron

Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

, or ductile iron

Ductile iron

Ductile iron, also known as ductile cast iron, nodular cast iron, spheroidal graphite iron, spherulitic graphite cast iron and SG iron, is a type of cast iron invented in 1943 by Keith Millis...

. Internal turbine elements can be plastic or non-corrosive metal alloys. they are accurate in normal working conditions to 0.2l/s however are affect greatly with dog mix interference.

Fire meters are a specialized type of turbine meter with approvals for the high flow rates required in fire protection. They are often approved by Underwriters Laboratories
Underwriters Laboratories
Underwriters Laboratories Inc. is an independent product safety certification organization. Established in 1894, the company has its headquarters in Northbrook, Illinois. UL develops standards and test procedures for products, materials, components, assemblies, tools and equipment, chiefly dealing...

(UL) or Factory Mutual
FM Global
FM Global is a U.S.-based insurance company, with offices worldwide, that specializes in loss prevention services primarily to large corporations throughout the world in the Highly Protected Risk property insurance market sector. "FM Global" is the communicative name of the company, whereas the...

(FM) for use in fire protection.

Fire hydrant meters are a specialized type of portable turbine meter that are attached to a fire hydrant
Fire hydrant
A fire hydrant , is an active fire protection measure, and a source of water provided in most urban, suburban and rural areas with municipal water service to enable firefighters to tap into the municipal water...

to measure water out of the hydrant. The meters are normally made of aluminum to be light weight, and are usually 3" capacity. Utilities often require them for measurement of water used in construction, pool filling, or where a permanent meter is not yet installed.

Compound meters

A compound meter is used where high flow rates are necessary, but at times there are smaller rates of flow that still need to be accurately measured. Compound meters have two measuring elements and a check valve to regulate flow between them. At high flow rates, water is normally diverted primarily or completely to the turbine part of the meter. When flow rates drop to where the turbine meter cannot measure accurately, a check valve closes to divert water to a smaller meter that can measure the lower flow rates accurately. The low flow meter is typically a multi-jet or PD meter. By adding the registration of the high and low meter registers, the utility has the total consumption through the meter.

Electromagnetic meters

Magnetic flow meter

The third most common flowmeter behind differential pressure and positive displacement flow meters, is the magnetic flow meter, also technically an electromagnetic flow meter or more commonly just called a mag meter. A magnetic field is applied to the metering tube, which results in a potential...

s, commonly referred to as "mag meters", are technically a velocity-type water meter, except that they use electromagnetic properties to determine the water flow velocity, rather than mechanical means which jet and turbine meters use. Mag meters use the physics principle of Faraday's law of induction

Faraday's law of induction

Faraday's law of induction dates from the 1830s, and is a basic law of electromagnetism relating to the operating principles of transformers, inductors, and many types of electrical motors and generators...

for measurement, and require AC or DC electricity from line or battery to operate the electromagnet

Electromagnet

An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...

s. Since mag meters have no mechanical measuring element, they normally have the advantage of being able to measure flow in either direction, and use electronics for measuring and totalizing the flow. Mag meters can also be useful for measuring untreated water, raw (untreated/unfiltered) water, and wastewater, since there is no mechanical measuring element to get clogged or damaged by debris flowing through the meter. Strainers are not required with mag meters, since there is no measuring element in the stream of flow that could be damaged. Stray electrical energy flowing through the flow tube can cause inaccurate readings, therefore most mag meters are installed with either grounding rings or grounding electrodes to divert stray electricity away from the electrodes inside the flow tube which are used to measure the flow.

Ultrasonic meters

Ultrasonic water meters

Ultrasonic flow meter

An ultrasonic flow meter is a type of flow meter that measures the velocity of a liquid or gas by using the principle of ultrasound. Using ultrasonic transducers, the flow meter can measure the average velocity along the path of an emitted beam of ultrasound, by averaging the difference in...

use an ultrasonic

Ultrasonic sensor

Ultrasonic sensors work on a principle similar to radar or sonar which evaluate attributes of a target by interpreting the echoes from radio or sound waves respectively. Ultrasonic sensors generate high frequency sound waves and evaluate the echo which is received back by the sensor...

transducer

Transducer

A transducer is a device that converts one type of energy to another. Energy types include electrical, mechanical, electromagnetic , chemical, acoustic or thermal energy. While the term transducer commonly implies the use of a sensor/detector, any device which converts energy can be considered a...

to send ultrasonic sound waves through the fluid to determine the velocity and translate the velocity into measurement of the water volume.

Registers

There are several types of registers on water meters. A standard register normally has a dial similar to a clock, with gradations around the perimeter to indicate water usage measured by the meter, as well as a set of odometer wheels similar to that in a car. Modern registers are normally driven by a magnetic coupling between a magnet in the measuring chamber attached to the measuring element, and another attached to the bottom of the register. Gears in the register convert the motion of the measuring element to the proper usage increment for display on the sweep hand and the odometer. Many registers also have a leak detector. This is a small visible disk or hand that is geared closer to the rotation speed of the drive magnet, so that very small flows that would be visually undetectable on the regular sweep hand can be seen.

With Automatic Meter Reading

Automatic meter reading

Automatic meter reading, or AMR, is the technology of automatically collecting consumption, diagnostic, and status data from water meter or energy metering devices and transferring that data to a central database for billing, troubleshooting, and analyzing.This technology mainly saves utility...

, manufacturers have developed pulse or encoder registers to produce electronic output for radio transmitters, reading storage devices, and data logging devices. Pulse meters send a digital or analog electronic pulse to a recording device. Encoder registers have an electronic means for an external device to interrogate the register for either the position of the odometer wheels or a stored electronic reading. Frequent transmissions of consumption can be used to give smart meter

Smart meter

A smart meter is usually an electrical meter that records consumption of electric energy in intervals of an hour or less and communicates that information at least daily back to the utility for monitoring and billing purposes. Smart meters enable two-way communication between the meter and the...

functionality.

There are also some specialized types of registers such as LCD display instead of mechanical odometers, and registers to output data or pulses to a variety of recording and controller devices. For industrial applications, output is often 4-20 mA analog, for the recording or control of different flow rates in addition to totalization.

Water meter reading

Different size meters may indicate a reading in different resolutions. One rotation of the sweep hand may be 10 gallons or 1000 gallons (1 to 100 ft.³, 0.1 to 10 m³). If one rotation of the hand represents 10 gallons, the meter has a 10 gallon sweep. sometimes the last number(s) of the odometer are non-rotating or printed on the dial face. The fixed zero number(s) are represented by the position of the rotating sweep hand. If one rotation of the hand is 10 gallons, the sweep hand is on 7, and the odometer shows 123456 plus a fixed zero, the actual total usage would be 1,234,567 gallons. A moving odometer wheel that has not completely turned over is counted as the lower number.

In the United States most utilities bill only to the nearest 100 or 1000 gallons (10 to 100 ft.³, 1 to 10 m³), and often only read the leftmost 4 or 5 numbers on the odometer. They would only read and bill using 1234 and rounding to 1,234,000 gallons based on a 1000 gallon billing resolution and the example above. The most common rounding for a particular size meter will often have different colored number wheels, the ones ignored being black, and the ones used for billing being white.

External links

Water Measurement Manual of the United States Bureau of Reclamation
United States Bureau of Reclamation
The United States Bureau of Reclamation , and formerly the United States Reclamation Service , is an agency under the U.S...
Utilimetrics - Non-profit industry trade association (Formerly known as the Automatic Meter Reading Association AMRA)
How to read different size water meters (PDF file)
How Meter Keeps Tab On The Water You Use, Popular Science, July 1950 very detailed article with good illustrations

The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.