What Is a Water Meter?
Water meters are meters that measure water flow. Most of them are cumulative water flow measurements. They are generally divided into volume water meters and speed water meters. They originated in the United Kingdom. The development of water meters has a history of nearly two hundred years. When selecting water meter specifications , You should first estimate the size and flow range of the flow that is usually used, and then choose the water meter of the specification that has the most commonly used flow closest to that value.
- Minimum flow rate (Q1): The minimum flow rate required for the indicated value of the water meter to meet the maximum allowable error.
- Boundary flow (Q2): The flow that appears between the commonly used flow Q3 and the minimum flow Q1, and divides the flow range into two areas, "high area" and "low area", each with a specific maximum allowable error.
- Traditional water meter
- There are two types of meter reading system: wireless and wired meter reading.
- There are two types of wired mode: 485 transmission mode and M-BUS transmission mode. The main characteristic of the 485 transmission method is four wires (two power wires and two signal wires), which need to distinguish the polarity of the wires; the main characteristic of the M-BUS transmission method is two wires, which are both power and signal And the two wires are not polarized.
- Wired meter reading can be divided into pulse type (active), camera type (passive), resistance type (passive), and photoelectric type (passive) according to different ways of technical implementation. In terms of technology reliability, development direction, and market share, photoelectric is the mainstream method.
- The meaning of the direct reading meter is that there is no power supply in normal times, and the meter is powered when reading.
- High metering water meter
- Using a water meter with a high level of measurement can make the water meter work in a large flow range including a small flow, and also fundamentally improve the sensitivity and measurement capacity of the water meter. Piston-type (also known as volumetric) water meters are generally rated at C or D levels, but have higher requirements for water quality.
- Note: Most countries in the world require the use of water meters that have a measurement level of B or higher, and there are calls in the domestic industry to cancel water meters that are rated A.
- In the new international standards and recommendations for water meters that have been drafted again,
- 1.Use inferior water meter
- 2. Water quality issues
- 3.Using long-term water meters and water meters without periodic verification
- 4. Unreasonable water meter installation [1]
- 1.Select water meter specifications
- Because the water meter has the best stability and durability under common flow, it meets the design requirements. If the water pipe has a margin in consideration of the future water flow capacity, the caliber specification can be one step lower when selecting a water meter. If the pipe with a diameter of 200mm has insufficient flow, you can choose to install a water meter with a diameter of 150mm. When the normal flow of the pipe with a flow of 200mm increases in the future, replace the water meter with the same diameter. Large-scale water-consuming industrial users can choose a large-caliber water meter when using a water meter, or use several relatively small-caliber water meters in parallel. This can also repair individual faulty water meters without affecting the user's normal water supply. Or change the table.
- 2.Select the type of water meter indication
- Generally speaking, the character wheel type is used for clear reading and easy reading. However, some people think that it is better to install the pointer type when the meter cannot be read at a short distance, because this type can judge the reading according to the geometric angle pointed by the pointer, without needing to see the value on the scale cylinder division. In recent years, liquid-sealed counters have become popular because they overcome the shortcomings of conventional counters that are prevented from reading by dirt and water in the water. The readings of remote water meters and prepaid water meters are displayed by electronic devices or collected and transmitted by collectors, but the base meter readings are still to be retained for comparison when there is a problem with the read electronic device .
- 3. Consider the convenience of installation and maintenance
- This is especially important for large-caliber water meters. Therefore, a water meter (such as a detachable water meter) that can be installed and replaced or repaired without stopping the water can meet these requirements. The installation length and connection method of the water meter are also a factor to be considered. Although the national standards for water meters GB / T778.1-1996, Tables 1 and 2 have stipulated this requirement, the water meters manufactured in accordance with this standard have an installation length and connection The way aspect is the same. However, in recent years, some new water meters (including pre-paid smart water meters) have not been manufactured in accordance with national standards but in accordance with enterprise standards, which may differ in this respect.
- 4. Consider water quality adaptability
- For various reasons, the quality of the water flowing through the water meter and the water interruption in many occasions is not as clean as in the water plant, and sometimes there are some impurities (such as rust, sand, hemp, etc.). In this case, in addition to considering the installation of some filters and other measures in the pipeline design of the water meter, the choice of a water meter or flow meter that can adapt to such water quality needs to be considered. [2]
- 1.The caliber of the water meter should be based on the
- There are three types of water-saving water meters on the market.
- 1. The first type of anti-drip water meter uses a magnetic pressure-sensitive element composed of magnetic material as the anti-drip mechanism and places it in the body of the water inlet. When the tap water flows outward in the form of a drip, The magnetic pressure sensitive mechanism will intermittently supply water to the water meter, so that the water meter is measured. This method can make the initial flow of the water meter less than 0.5 L / H. Most afraid of impurities such as rust, iron and mud in the water, the magnetic column is most likely to be caught by impurities in the water and no longer has the function of preventing dripping;
- 2. The second type of anti-drip water meter is to use a small tube or a small hole to lead a small flow of tap water to the impeller box of the water meter, and align the impeller of the watch core to spray, concentrating the water kinetic energy of the small flow at one point to push the impeller. , So that the impeller rotates to achieve the purpose of measuring the small flow rate. The water meter in this way can achieve a starting flow rate of 2 L / H. Will cause more metering of the water meter, which will cause the water meter to have greater latent movement due to the instability of the water pressure in the water pipe network (that is, when the user closes the faucet without using water, the water meter is caused by the instability of the water pressure in the pipe network. The phenomenon of idling) is generally up to 192 liters per day (a month s tap water of 5-6m & sup; even if not using water), causing users to pay water charges unjustly, resulting in user complaints and refusal to pay for water This phenomenon occurs. Another drawback of this structure is that it is easy to be blocked and stuck by mud and sand. After a period of time (usually three to five months), it will lose its anti-leak effect;
- 3. The third type is a diaphragm integral type anti-drip water meter. It is an additional cavity at the bottom of the case of an ordinary water meter. The upper structure is still the same as that of an ordinary water meter. A soft diaphragm is used to seal and separate the bottom cavity. The body is in communication with the water outlet of the water meter case. There is a special anti-drip mechanism in the water outlet. When the tap water leaks out in the form of a drip, at first the anti-drip mechanism still closes the outlet of the water meter. The water dripping outward is actually the water meter. The water in the bottom cavity, after the drip of the bottom cavity (36 ml in volume) is completed, the anti-drip mechanism will be opened to replenish the discharged water to the bottom cavity, and the water in the cavity will be replenished. After completion, the anti-drip mechanism seals the water outlet of the water meter under the action of the spring, and enters the next cycle. The process of replenishing water to the bottom cavity when the anti-drip mechanism is opened is a process that is greater than the starting flow of the water meter. Can be measured.
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- A stands for basic type, seven-position pointer, combined impeller, scale 1L [4] ;
- B stands for combined impeller, 8-digit pointer, and minimum verification index 1L;
- C represents the overall impeller, 8-digit pointer, and the minimum verification index is 0.1L;
- E stands for integrated impeller, 4-digit pointer 4-digit word wheel combined counter, and the minimum verification index is 0.1L. Among them, the A-type meter is the first improved design of the original unified design water meter.
- Note: The basic water meter is also commonly known as "seven-digit pointer water meter" in the industry.
- Model example:
LXS-15C represents a rotor-type water meter with a nominal diameter of 15mm and a third improved design (integral impeller, 8-digit pointer);
LXL-80 represents a horizontal screw-type water meter with a nominal diameter of 80mm;
LXSL-20E stands for rotor type vertical water meter with nominal diameter of 20mm