November-December 2006

Water Meters and Automatic Meter Reading

As the saying goes, knowledge is power. In the business of water metering, up-to-date, real-time, accurate knowledge of water use as expressed in flow rate data allows for accurate assessment of water usage, which is of vital importance in keeping utility bills low and conserving water in drought conditions.

Each of the various types of water flow meters can be connected via simple interface units that transmit data to electronic collectors and management computers. Such systems reduce overall costs by eliminating most labor costs traditionally associated with meter reading and allow for the most efficient use possible of available water resources.

Types of Water Meters
Most commercially available water meters use one of three methods for measuring flow rates: displacement, velocity, and electromagnetic.

Displacement metering is the method of choice for small to medium flow applications. This is why displacement meters are most commonly used in residential applications and for measuring water use by small businesses. Water flows through a displacement flow meter and physically moves like (causes positive displacement of) either an oscillating piston or a nutating disk. In the oscillation piston type, the flow spins a rotating wheel attached to a piston’s displacement arm that causes the piston head to move in and out of its sleeve. A nutating disk wobbles on its axis directly as the water flows past it and causes it to spin. In both cases, the speed of movement increases with increased flow. Both types of displacement mechanisms are attached to magnets. These magnets move a register that records speed and number of rotations per time period and translates these measurements into flow rates for reading and recording. Most displacement meters are relatively small, less than 2 inches in size. They also come equipped with built-in strainers that intercept debris floating in the water flow that could damage or break the measuring mechanism.

Velocity-type water meters use jets of water impacting on impellors that turn on their axle while moving the register. These impellors are usually adjustable so the meter can be calibrated to the necessary degree of accuracy. The meters are sized so that the velocity of the jets can be accurately translated into impellor rotary speed. With a fixed-diameter inlet port, the resultant velocity can be converted into volume flow. In a single-jet velocity meter, a single stream of water impacts the impellor. Multi-jet meters use multiple ports that surround the housing, which inject water streams against the impellor. Like displacement meters, velocity meters are best suited for relatively small flow measurements associated with residential and small-business water use. Since they are not as accurate at large flow rates, their use is usually restricted to water lines 2 inches in diameter or smaller. The direction of the incoming flow is at right angles to the impellor axis, which spins like a miniature water wheel. As with displacement meters, their internal mechanism can be damaged by debris so velocity also comes with internal strainers to remove debris before it can impact the impellors.

In high-flow situations where displacement and velocity meters cannot be used, turbine meters are appropriate. Similar to single-jet meters that measure flow rates by the rate of an impellor’s spin, turbine meters measure flow by the rate of spin induced in an in-line turbine. Unlike the velocity meter’s impellor axis, the turbine’s axis of spin is collinear with the direction of water flow. The water passes around the turbine, impacting its tilted blades and causing it to spin in an action similar to that of a power-generating turbine being spun by high-pressure steam. More force is required to spin a turbine than an impellor, so these types are more suited to larger flow rates. Most often they are used in large industrial processes, firefighting, and entire community water distribution systems. As with the other meters, turbine meters also require protection from floating debris and are equipped with in-line strainers. Turbine meters can be installed in water lines as large as 12 inches in diameter.

When water flow rates are highly variable, a compound meter is appropriate. As the name suggests, compound meters have two measuring components, one for high flows and another for low flows. To prevent backflow between the two, the meter is equipped with a check valve. As water flow rates drop, the pressure inside the meter falls and the check valve closes. This diverts the flow to the low-flow rate measuring component (typically a velocity meter).
Electromagnetic flow meters (“mag meters”) are a kind of velocity meter that uses the electromagnetic properties of water instead of mechanical turning mechanisms to measure stream velocity and flow rates. They have no moving parts, which make them ideal for measuring wastewater flows, slurries, and other liquids with debris or contaminants that could damage a mechanical meter, and have no need for strainers. Their operation is based on Faraday’s Law: The voltage induced across any conductor as it moves at right angles through a magnetic field is proportional to the velocity of that conductor. The magnets surrounding the pipe create a magnetic field across the entire cross-section of the flowing liquid. The flow generates voltage as it crosses the force lines of the magnetic field. The strength of this voltage translates electronically into water flow rates. Insertion-style flow meters are placed in the center of the pipe flow, creating magnetic fields outward through the surrounding water.

Automatic Meter Reading
Those of us of a certain age can remember the monthly visits to our homes by the meter man who would read the numbers on our water meter and manually record them in his logbook so we could be sent a water bill the following month. While this still happens in many areas, this job has “fallen victim to automation” and has been replaced with automated meter readers. Automated meter reading (AMR) is a technology that automatically performs what was once a manual data collection operation and transmits these data back to the utility for recordkeeping and billing. This allows for real-time measurement of water use and accurate billing based on actual consumption instead of estimates based on past usage.

While differing in detail, most AMR systems consist of the following components:

• Meter interface units (MIUs). These units perform the actual “reading” of the meter and can be either integral to the meter or an add-on component. MIUs collect, process, and store water meter readings in real time. They also act as transponders, sending this information via radio frequency or cable. For this transmitting, the MIU includes a radio antenna linked to a transmitter unit.
• Mobile interrogators that communicate with the MIU via two-way radio frequency links. They retrieve appropriate data and meter readings. Mobile interrogators can be handheld or vehicle transported. They can access data from dense and scattered MIU sites depending on the range of the radio transponders. Links to the transponders are encoded with each transponder’s unique serial number. Typically the mobile interrogator broadcasts a request to the MIUs, which respond with water meter data for the requested date and time.
• Route management software utilized by central data recorders and billing computers. This software processes and collates the data from the various reading routes provided by the interrogators. Once it receives the information from the interrogators, the software stores it for future retrieval by the central information and billing system.

Photo: Honeywell

Installation of AMR systems, the advantages of which include real-time water-use measurement based on actual consumption

Photo: Honeywell

As for the radio frequencies used for communication between the various AMR system components, there are three types: handheld, mobile, and fixed relay networks. They can in turn be based on four telephony platforms: wired, wireless, radio frequency, or transmission along power lines.

Handheld AMR systems can be touch based. In this system, a meter reader physically touches the MIU with a probe making contact with the device and automatically collecting its data. The probe sends out an interrogator signal and in return receives an answer from the MIU, matching the data to a prerecorded serial number for the meter being read. This system has aspects of both old and new, with automatic readings but still dependent on human meter readers.
Mobile units are mounted on vehicles or backpacks and rely entirely on wireless radio frequency communication. These drive-by readings are conducted on a monthly basis with both the mobile units and the MIUs sending and receiving information. Fixed relay systems can be either wireless or via cable, with the signal sometimes sent along the power lines themselves. These can be interrogative in nature or what is referred to as “bubble up” systems, where unprompted MIUs transmit continuous readings every few minutes. In mobile systems, the human operator is nearly eliminated, except for the driver of the vehicle whose interrogator unit is accessing multiple MIUs simultaneously. In fixed relay systems, the human operator is completely replaced.

Manufacturers and Suppliers of Water Meters and AMR Systems
Itron provides both flow meters and AMR systems. The company’s Centron model meter and poly-phase meter provide platforms for AMR systems as well as provide accurate metering of utilities. Both have solid state data recording hardware with the poly-phase equipped with multifunctionality. Similar to the poly-phase meter, the Sentinel model is designed for use in high-capacity industrial and commercial applications. A full range of AMR hardware allows for operational flexibility ranging from handheld interrogators to global positioning system (GPS)–based mobile collectors to high-end fixed networks. These systems are all tied together by PC Pro Advanced data management software, which allows the system operators to do everything from adjusting for changing use patterns to troubleshooting deployed meters.

Photo: Master Meter

Operating with very low head loss, the MMPD positive displacement meter can pass floating debris and solids without damage.

Honeywell, a global leader in energy services, is also a leader in AMR deployment. The company’s Utility Solutions business offers turnkey deployment services and performance AMR packages for its clients. The goal of performance AMR is to provide a self-funding system (the upfront cost of installing the system is matched by the subsequent labor cost savings and overall efficiencies) that is customized for each application. Honeywell follows up with a suite of offerings, including system startup, full program management and administration, data system management, safety training and practices, Six Sigma quality assurance, performance guarantees, and financing. Its value-added services also can include water audits and management of water conservation programs.

Master Meter manufactures all kinds of flow meters (multi-jet velocity meters, displacement meters, turbine meters, and compound meters) along with compatible AMR systems. The company’s multi-jet meters range in size from five-eighths-inch to 2 inches and are designed with future upgrades in mind. Modular Register design allows for simple upgrades and the ability to add on new technologies without changing out the entire meter. The MMPD positive displacement meter has sufficient capacity to pass floating debris and solids without damage and operates with very low head loss (6.5 psi at 20 gpm). The high-flow-capacity MMT series turbine flow meters come as large as 12 inches. Equipped with nylon inlet flow conditioners, these meters are designed for durable operation and long operating lifetimes. Master Meter’s Dialog class AMR hardware includes two drive-by systems (the 3G-DS-RF and the 3G), both utilizing an absolute encoder, which determines the odometer reading so as to provide a perfect match with the mileage and the electronic reading. Complementing this are the company’s handheld units and fixed base LAN system.

Transparent Technologies provides an AMR system that combines a GPS with interactive AMR. The software is run on standard laptops, reducing the need for specialized hardware. Its database management software is open-source Microsoft Access. The GPS allows accessing individual MIUs by touching their locations on the laptop screen via Microsoft Map Point Access. Additional features include leak detection. The system looks for leaks by detecting flow during anticipated periods of no flow (late at night, for example). If the system’s MIU does not detect a “no flow” situation during this time, the leak detection icon flags the location. Similarly, the system can detect backflow and potential cross contamination from sewage lines by detecting reverse flows in the water supply pipeline. By combining a projected high usage threshold with a designed conservancy period (e.g., three days a week), the system can detect violators of designated water conservation periods. The mobile radio interrogator has enough memory to record the last 16,000 meter readings. With readings taken hourly, this is equivalent to 21 months of water-use data.

Radix International Corp. is a leading manufacturer of portable computing equipment for AMR use with an international customer base. Radix is a manufacturer of equipment and hardware essential to the operations of AMR. This includes its FP series of portable printers and printer interfaces, and its FW series of handheld field computers utilizing PC DOS or Microsoft Windows CE Net operating systems. The FW computers are all designed for rugged durability in the field and (depending on the model) come with touch-sensitive screens, LCD displays, and manual keyboard input.

Photo: Master Meter

Durable, long-life MMT turbine flow meters may be as large as 12 inches.

The Neptune Technology Group is a supplier of complete AMR systems to a variety of utilities. Recently, Neptune has joined forces with Landis+Gyr to develop an AMR system that combines its R900 field module with Landis+Gyr’s meter platform. Neptune’s suite of interrogators (both handheld and mobile) is compatible for use with any utility’s R900 metering application. With the acquisition of DB Microwave, Neptune can provide a library of in-house software (Fieldnet, or Equinox) for meter reading. The company’s meter reading hardware includes compact, such as its CE 5320X handheld, and the MRX920 Mobile Data Collector (a laptop system that collects data via radio frequency and in turn transmits these data to the customer information system). Augmenting these mobile systems is Neptune’s EZGate fixed data collector. This hardware collects, stores, and manages meter readings from commercial customers, industrial accounts, and specialty applications via landlines or cellular telephone modems.

Metron Farnier specializes in high-end single-jet velocity flow meters. Its Spectrum series water meters have the highest range of any water meter on the US market with a 1,000:1 turndown range while maintaining accurate flow measurements. The meters’ simple design combined with high-quality and high-strength materials makes them less vulnerable to inflow debris and allows for minimum maintenance even under adverse operating conditions. Easily installed on any pipeline segment (there is no need for a minimum straight pipe length either before or after the meter), Spectrum meters are compatible with any AMR system on the market. Derived from the Spectrum’s impellor design, the Enduro series of water meters incorporates a modified configuration where the measuring device does not extend across the entire cross-section of the water flow. This allows for unobstructed high flows and prevents meter-induced head losses in the pipeline. Metron’s newly developed line of handheld readers, MIUs, MIU interface software, AMRs, and AMR interface software are all compatible with its water flow meters. The company’s data gathering handhelds are unique in that they rely on standard Palm units but utilize infrared technology for the signaling.

Liquatec provides a line of flow meters and compatible in-line filters. The company’s PMF series wall-mounted flow meters are constructed of durable acrylic and stainless steel. Cost-effective meters derived from injection molding technology, the PMF series provides metering from 0.2 gpm to 10 gpm. In keeping with the company’s philosophy of simple design, Liquatec’s SDF series of sediment filters consists of various diameter cartridges (easily installed and removed) of spun polypropylene.

Fixed network AMR systems are the specialty of Hexagram Inc. These systems include meter transmission units, data collector units, network control computers, and customer service and metering computers. Hexagram’s Star system water MIUs are integrated with water meters, sending pulsed data transmissions every five minutes on an FCC licensed wireless channel. They are compatible with pulse and encoder meters from all manufacturers. STAR MIUs can be manufactured in multi-port configurations, capable of reading more than one meter or service installation. The MIUs transmit their signal to the Star data collection units. These are intelligent monitoring units that forward the data from the MIUs to the Star network control computers via fiber optics, wi-fi, cellular, and wireless. These computers collect, validate, process, and store the transmitted data so that the system can provide billing and customer services.

Datamatic’s FIREFLY water meter interface units attach to any commercially available water meter in a matter of minutes. They utilize a unique optic sensor that does not need electronic output registers, which eliminates the requirement for meter changeout because of its complete compatibility. The untis can detect leaks and tampering, while utilizing straight/direct-read, pulse, and encoded registers. Their data storage capacity allows for the storing of 74 days’ worth of hourly meter readings. The data are managed by Datamatic’s ProfilePLUS software system that provides analysis of consumption rates, conservation compliance, and leak detection.

Ready-to-use AMR platforms are provided by Coronis Systems, which offers two different solutions for meter reading by fixed networks. The Local Wavenis area network is suitable for local wireless systems utilizing its technology by modules connected to a personal computer and can have a range of up to several kilometers. Complementing the local network is Coronis’ Extended Wavenis area network. This allows networks to perform AMR functions over much greater distances using GSM modems or a server with WAN capabilities. Radio coverage can be extended through repeater modules. The modules and similar equipment allow its users to manage their Waveflow wireless meter monitors.

Controlotron (recently acquired by Siemens) manufactures several lines of hydrocarbon, industrial, chemical, and residential flow meters. The company uses exclusive Wide Beam transducers that provide accurate flow measures no matter what kind of liquid is being measured or its temperature. For ease of maintenance, they are maintainable without the need for open pipelines or stopped flow. Controlotron’s meter interface units provide both digital and analog data outputs. Its model 1010P is a convenient, battery-operated, portable clamp-on flow meter and is used to check the calibrations of permanently installed flow meters. Its 1010N and 1010X utilize sonic Doppler flow measurements for virtually any liquid, even those that are highly aerated. The model 1020 is a low-cost flow meter incorporating an integrated flow transducer and computer mounting package.

Photo: Master Meter

Dialog AMR hardware features two driveby systems with an absolute encoder.

BIF supplies flow meters for both the water and wastewater industry. Its universal Venturi tubes are differential flow metering elements. Their dimensions and shape allow for reliable measurement of flow. Model 20181 is made from cast iron and is used for water, sewage, and other liquid flows. The corrosion resistance Model 20182 is made from reinforced fiberglass and can be easily inserted at pipeline flange joints. The multiple uses of the Model 20183 are due to its fabricated designs and low head losses. A unique square Venturi tube design is provided by the Model 21084 and eliminates the need for long transition runs when using a circular flow metering device in rectangular channels.

Badger Meters manufactures a wide assortment of meters for almost every industrial and commercial use. The Recordall Turbo series varies in size from 1.5 inches (measuring flows from 2.5 gpm to 200 gpm) to 20 inches in diameter (measuring 200 gpm to 19,800 gpm). The company’s Magnetoflow Mag Meters range even larger from 2 inches to 54 inches. The Turbo meters utilize a floating rotor design (without bearing wear friction) that reduces wear and tear and minimizes maintenance while maximizing operational life. Suitable for large-scale flow measurement, the Turbo meters are compatible with Badger’s AMR system. The mag meters are non-intrusive clamp-on modules designed to measure sewage and other types of flows. Tying these together are Badger’s encoders, which are the heart of its AMR system, allowing for reliable data links to handheld data collectors, touch and read systems, radio frequency systems, low earth-orbiting satellites, and fixed base relays.

AMCO manufactures displacement, turbine, and magnetic flow meters. Its Aquamaster electronic water meter is designed to be a replacement for mechanical meters while providing higher-accuracy electronic metering. Bulk metering is performed by AMCO’s T3000 and T4000 class turbine meters, with a modified model C3000 providing a compound metering system.