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1. Background

In 1998, water supply companies in various regions fully established the "meter reading at home" for urban water supply. The National Planning Commission and the Ministry of Construction: Document No. 1810 of the State Planning Commission and the Ministry of Construction on Urban Water Supply Price Management [1998] clearly pointed out that urban water supply should implement meter installation at home, meter reading at home, and metered charging

2. Due to the increase in the workload of meter reading and charging, it is imperative to choose smart water meters.

At present, the so-called smart water meters are generally divided into two categories: one is called the smart card water meter series; the other is called the smart remote meter reading series. This article focuses on the characteristics and selection of smart card water meters.

The card water meter is mainly composed of four parts, namely: base meter, valve, circuit and battery.

When choosing a card water meter, the following aspects should be considered:

1) Waterproof and moisture-proof performance.

Smart card water meters are electromechanical products. Since they are battery-powered, they must be designed with micro-power consumption to ensure that the battery working time is greater than 6 years (according to industry standards). The installation and use environment of the water meter is relatively humid. If the waterproof and moisture-proof is not done well, it is easy for moisture to enter the meter, causing circuit leakage or corrosion, and causing the water meter to have "black screen" or "valve failure". Therefore, when choosing a card-type water meter, the first thing to understand is the waterproof and moisture-proof performance of the meter. Two simple test methods are recommended:

① Spray method: Put the water meter under the faucet for 1~2 hours, take it out and expose it to the sun, observe whether there is water mist on the display, and whether the switch valve of the water meter is normal.

② Soaking method: Soak the water meter in water for about 1~2 hours, take it out and observe for 1~2 days to see if there is water mist on the display, and open the case to see if there is water mark in the meter. Water mist or abnormal function indicates poor waterproofing.

A water meter with poor waterproof and moisture resistance must have a short life.

2) Battery performance.

The battery is the power source of the water meter. If the battery is not selected well, there will be no problem at first, but after one or two years, the valve will not open or close, the card reading will not work, and the display will not be able to display.

Smart water meter batteries generally choose disposable lithium batteries. Lithium batteries are divided into two categories, one is 3.0V lithium manganese lithium battery, and the other is 3.6V lithium erbium battery.

Among them, lithium financial industry batteries have high voltage and easy circuit design, but there is a big disadvantage, that is, if they are not discharged for a long time, the battery is easy to "passivate". "Passivation" is like a water pipe gate that is not used for a long time and rusts. After "passivation", the battery cannot provide current, resulting in the inability to drive the valve. Water meters that choose lithium erbium batteries generally design periodic discharge circuits. If the design is not good, "passivation" will also occur.

The other type is lithium manganese batteries. This type of battery has low voltage and more complicated circuit design, but there will be no "passivation" phenomenon. We recommend that lithium manganese batteries should be used for smart card water meters, and it is best to use imported ones. Although the cost is higher, the performance is stable and the life span will be about 50%-100% longer than that of domestic ones.

3) Selection of valves.

Valves are important components of smart card water meters. In the domestic market, there are three main types of valves selected for smart card water meters: ball valves, pilot valves and ceramic valves. The three types of valves have advantages and disadvantages. Since the valves selected on the water meter are battery-driven, the general principle should be small rotation torque, not easy to be stuck by debris, not easy to cause misoperation, and small pressure loss. In particular, attention should be paid to the local water quality. If the sand or calcium and magnesium ions in the water are high, it is best to use stainless steel ball valves, which are not easy to be stuck and scaled.

4) Selection of base meter The base meter is generally composed of two major parts: the case and the movement. There are currently three main types of smart meter cases, namely: iron case, steel case, and engineering plastic. The iron case can easily rust and make the valve torque heavier, causing the valve to lose control. Copper shell is currently a widely used material for watch cases. Long-term use will not have any effect on the performance of the watch, but attention should be paid to the lead content in brass. Excessive lead will affect the water quality. Engineering plastics are a new type of watch case material. At present, water pipes have been widely used in this type of engineering plastics. I believe that in the future, they will also be widely used in the selection of water meter cases, but the material's health and safety indicators, compressive strength, and anti-aging performance must meet the relevant national requirements.

The movement of smart watches is generally divided into two categories: wet movement and dry movement. Wet movement is generally more sensitive, but the surface plate is prone to yellowing and freezing cracking when there is water. The impeller and display wheel in the dry watch are driven by magnetic coupling. The display wheel is dry and will not be contaminated by scale in the water, and the panel can remain clear for a long time. However, due to the magnetic coupling, a certain friction must be overcome during transmission, so the sensitivity will be reduced a little. At present, our company has developed a fully electronic smart water meter that can overcome the above shortcomings by sampling from the impeller and directly displaying it electronically.

3. Selection of manufacturers

Selection of smart card water meter manufacturers: There are nearly 100 manufacturers of smart card water meters available online, with large differences in production scale and product quality. In particular, some companies cannot solve the problems of products in time, and some even simply close down and leave, which brings great trouble and losses to users and has a negative impact on the entire smart water meter industry. Therefore, when choosing a meter, you should first understand its manufacturer and its history. You should be more cautious when choosing a newly established company and understand its technical strength, because most smart meter companies currently have almost no R&D team of their own, and they are assembled by buying other people's modules. Once such companies have problems with their products, they cannot solve them by themselves and ask for help from others. In addition, before purchasing a smart water meter, you should also understand the user use and feedback of the brand's products, the annual failure rate of the product, and the after-sales service team to protect customer rights.

4. Installation and protection of smart card water meters

Installation and protection of smart card water meters. Smart card water meters contain batteries and circuit boards. When installing, pay attention to installing them in a dry place that is not easily exposed to water. If installed outdoors, they should be protected by a meter box and should not be exposed to direct sunlight or rain, otherwise it will affect the service life, because the leakage and self-discharge of the battery in the meter will accelerate in a damp and high temperature environment.

In winter, special attention should be paid to antifreeze, because the volume of water will increase by about 10% after freezing, and any pipes and water meters will be difficult to withstand huge pressure. In the north, many newly built buildings every year have water meters that are frozen and cracked because they have no heating but water supply, which should attract the attention of the water supply department.