Reading meters by radio
Radio is used in 90% of the AMR meters installed around the world, making reading meters by radio the fastest growing segment of the AMR industry. It involves retrofitting an existing meter with an AMR module that contains a radio transmitter and sometimes also a radio receiver. New meters can also be purchased from meter manufacturers with radio AMR capability built in.
AMR meter modules are available for electricity, gas and water meters. Several speciality applications are also available, including heat allocators and tank level monitoring. AMR modules work by interfacing to the meter electronics, or in the case of mechanical meters by sensing the mechanical motion that drives the mechanical register.
Radio AMR meter modules operate by transmitting periodically, or by responding to a radio interrogation. Periodic transmitting relies on either a fixed receiver being present nearby, or a mobile radio in a handheld computer or mounted in a vehicle coming within range when meter data is required.
The operation of radio AMR meter modules falls within the regulatory agencies of each country. These regulations determine the radio frequency, the transmitter power levels and other technical characteristics of radio operation. The specific regulatory requirements can make the difference between a cost-effective system, and one that is too expensive to use except for high cost to read meters.
Radio AMR meter modules in the United States generally operate at 900 MHz; in the UK 184 MHz has been allocated for meter reading, and in continental Europe 433 MHz is generally used. In the US the radio band is shared with many other users, and spread spectrum modulation techniques are encouraged. In Europe and the UK narrow band operation is required.
Radio is, of course, only one of several different communication methods. The other most common method is telephone. About 10% of AMR devices installed world-wide communicate by telephone. The only other technology with any significant installation is power line carrier (PLC, also known as mainsborne).
What governs the decision to opt for radio, telephone or PLC? The choice is almost always made on cost. Meter reading is usually a relatively low cost activity, even when done manually. Replacing or augmenting manual handheld computer-based systems with AMR requires that operational costs be lowered, or that some additional benefit be gained.
Because of the high labour cost of installing wires, radio is almost always the least expensive technology for AMR. But there are circumstances which can drive up the cost of radio and lead to another technology choice. The most common of these is regulatory (ie, the radio regulation requirements). Regulatory requirements that do not provide for AMR operation can leave radio AMR systems with no spectrum in which they can be used.
Radio regulations that have been developed for the world of fixed and mobile radios frequently require the use of very narrow channels with very precise stability requirements. Although the technology for using narrow frequency bands with high precision is well known, such technology is very costly compared to the requirements of AMR.
Certain environmental factors may require special consideration. Depending on where the meter is located, there may not be a clear path for the radio signal to reach the radio receiver in a handheld computer, vehicle or pole mounted unit. Repeaters can be used to supplement such installations and are often needed in apartments, high rise buildings or densely populated central city areas.
However, the most common circumstance where radio may not be the lowest cost solution occurs when meters are remotely located. If there is telephone service available, telephone is almost always the best choice for rural or remote meters. Since the service area of almost every utility includes a mix of remote, rural meters and suburban or city populations, a superior AMR system offers a mix of technologies that bring meter reading data to a common database for transfer to the utility billing or customer information system.
There are also speciality radio solutions for remote meters where no telephone service is available. A number of companies have launched satellite systems into low earth orbit (LEOs). Because they are much closer to the earth than the satellites used for telephone communication or television broadcasting, they can communicate directly with radios on the ground without the requirement for large dish antennas. Although a satellite radio AMR device is about ten times more expensive than ordinary radio meter modules, for very remote meters located at pump stations, wellheads, pipelines and so on they may still be more economical than sending a meter reader to such remote locations.
PLC is used almost exclusively for communicating between various control and switch points within a building. Power lines are a noisy environment, and the challenge of communicating reliably and interfacing safely to the high voltages found on power lines all add to the cost of this technology. There are the additional difficulties of installing wires to gas and water meters with the appropriate regard for safety, especially in the case of gas meters. In most urban and suburban areas, radio will almost always be the most cost effective AMR technology, often less than half the cost of PLC.
Genesis by Itron is a family of products offering a variety of communication technologies that collect data into a common database for presentation to utility application systems. It relies mainly on radio technology, but the Genesis family also includes telephone technology for both gas and electricity meters. Itron works with suppliers of PLC and satellite communication to present customers with a total solution.
Table 1: Benefits of Wireless Fixed Networks
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