The advantages of solid state meters when compared to moving parts mechanical meters range from dependable long-term accuracy and tolerance to grit and air, to lower whole life costs, fewer customer disputes and more workable prepayment systems. These new technologies lend themselves to radio and other types of AMR (automatic meter reading) since the signal output is electronic, and does not rely on an electromechanical interface between the meter and the AMR medium.

The less complicated, visual read-only meters are now available in the solid state format; hence the advantages of the new systems are not exclusively reserved for the high-tech end of the metering spectrum.

A GLOBAL TREND

Solid state electronic water metering at the volume domestic level has been around for a number of years, but has somehow not quite taken off. This is changing dramatically as major water companies increasingly ask for solid state meters, or even specify their exclusive use. The growing interest in solid state technology is feeding on an expanding base of trials and research taking place across the globe – from the Middle East to Australia, and from the US, India and Korea to Micronesian islands in the Pacific.

The spur in the development of new technologies was initially the high tolerance to grit and air contamination of water supplies. Many of the original trials were in areas where these two problems had effectively undermined the whole process of domestic water metering. However, the reduction in costs and the inherent advantages of the system are now attracting mainstream users across the world – even in simple visual read-only situations.

Some major players in water metering are already active in the market. Comparative trials are underway, particularly in the Gulf region of the Middle East, with different types of solid state meter. However, the company with undoubtedly the most experience of this type of product, and the largest number of domestic installations of solid state meters, is Severn Trent Metering Services, based in England.

BEWARE OF IMITATIONS

The first thing to bear in mind is that meters which describe themselves as electronic are not necessarily solid-state meters. The guts of the meter may retain the old moving part technology, but manufacturers put an electronic counting unit on top and call it an electronic meter. These meters will not offer the advantages of solid state technology.

CHOICE OF SYSTEM

There are at least three different ways to meter water without using the old moving part technology, although new systems may soon emerge.

Ultra-sonic. A sound wave is generated within the flow of water in a pipe. The speed at which this wave travels through a known length of pipe is proportional to the speed of the water in the pipe. By measuring the apparent speed of this wave compared with a known standard, the rate of flow of the water in the pipe can be estimated.

Electro-magnetic. Water is a conductor of electricity and produces an electrical charge when it moves through a magnetic field. The size of this charge is proportional to the speed of the water going through the field. By applying a strong magnetic field inside a known pipe dimension, the rate of flow of the water can be determined.

Fluidic Oscillation. When water passes through a precisely shaped chamber, regular side to side oscillations are induced in the flow of the water. These disturbances in the flow can be detected by various means (fluidic oscillation technology has been available for many years, and a number of different types of oscillators have been developed). Each oscillation represents a very precise volume of water, which can be counted.

In the first two systems, water volume is estimated from the rate of flow of the water, whereas the fluidic oscillator system has more similarity with volumetric measurement. However, in all three cases the overall advantage is that there are no mechanical moving parts within the water flow to wear out or jam.

THE FUTURE LIES WITH SOLID STATE

In the case of the fluidic oscillator meters produced by Severn Trent Metering Services, the meters retain a near 100% accuracy over their lifetime, which is long compared with mechanical meters. The meter has a battery which will last for a minimum of ten years and can be very cheaply replaced, extending the meter’s active life for a further ten years.

This long active life combined with the intrinsic accuracy makes these meters arguably the most cost-efficient units on the market. This cost advantage, together with the additional advantages of electronic functionality, makes it easy to see where the future of water metering lies.