cold water meter
Outline of Smart water meter(AMR water meter) 2019-09-17
Smart water meter

Smart water meter is a new type of water meter that uses modern microelectronic technology, modern sensing technology and smart IC card technology to measure water consumption and conduct water data transmission and settlement transactions. Compared with traditional water meters, which only have the functions of flow collection and mechanical pointer display of water consumption, it is a great improvement.  In addition to recording and electronic display of water consumption, the smart water meter can also control the water consumption according to the agreement, and automatically calculate the water fee for the ladder water price, and can also perform the function of water data storage.


Introduction

Smart water meter is a new type of water meter and traditional water meter that uses modern microelectronic technology, modern sensing technology and smart IC card technology to measure water consumption and conduct water data transmission and settlement transactions. Generally, it only has flow collection and mechanical pointer display water consumption. Compared to the features, it is a great improvement. In addition to the recording and electronic display of water consumption, the smart water meter can also control the water consumption according to the agreement.

Advantages

  1. It can record and electronically display the water consumption;
  2. It can control the water consumption according to the agreement, and automatically calculate the water fee of the ladder water price, and at the same time can perform the function of water data storage;
  3. Data transmission and transaction settlement The IC card is carried out, which has the characteristics of convenient transaction, accurate calculation and bank settlement.
water meter installation
1. Select the correct diameter of the water meter;
  2. Install horizontally with the surface facing up, and the direction of the arrow on the case is the same as the direction of water flow. The installation location should avoid exposure, flooding, freezing and pollution, and facilitate disassembly and assembly and meter reading. Newly installed pipes must be cleaned of gravel, hemp and other debris in the pipeline before refilling the water meter to avoid water meter failure;
  3. Install valves on the upstream and downstream of the water meter, and ensure that all are opened when used;
  4. Install upstream and downstream of the water meter The necessary straight pipe section or its equivalent rectifier requires that the length of the upstream straight pipe section is not less than 10D, and the length of the downstream straight pipe section is not less than 5D (D is the nominal diameter of the water meter). For the eddy current phenomenon caused by the elbow or centrifugal pump, the rectifier must be installed in front of the straight pipe section.
  5. When installing the water meter, it should be noted that the water outlet of the downstream pipe of the water meter is higher than the water meter by more than 0.5m, so that the water meter is insufficient due to the water flow in the pipe. The metering is incorrect.
  6. The water meter has excellent anti-clogging performance, but it is sensitive to siltation and weeds in the pipeline, and should be avoided during use. If there are silt and weeds in the pipeline, it should be cleaned up in time, otherwise it will affect the normal metering of the water meter.

Considerations

1. After replacing the battery, you must cover the moisture-proof cover and tighten the screws. Otherwise, the watch will not work and the card will display E--5.
  2. Regularly check the operation of the smart water meter and pay attention to the antifreeze in winter.
  3. If the valve has been installed in the pipeline but has not been delivered or is not used for a long time (more than one week), please close the front and rear valves of the smart water meter. The company will not bear the consequences.
  4. If the electronic display of the smart water meter does not match the character wheel or the smart water meter fails, the word wheel measurement shall prevail.
winter protection points
First: water-based products must be well protected against moisture and freezing. Although the smart water meter has advanced intelligent technology, it does not mean that the smart water meter “water and fire does not invade”. In order to ensure the normal operation of the water meter, it is best to check the water meter regularly. The temperature in winter is low. Keep warm and pay attention to cover the moisture. cover.
  Second: Avoid contact with corrosive substances. Corrosive substances are fatal to the damage of smart water meter precision instruments and must not be touched. In addition, strong collisions and impacts can also cause damage to smart water meters.
  Third: Do not use the instrument with strong magnetic or other strong interference function to approach the smart water meter, otherwise it will cause the function of the smart water meter to be confusing, or even directly “strike”.

Metering characteristics

1. Conditions of use: water temperature 0.1~30°C
2. Water pressure rating: MAP10
  3. Climate and mechanical environment Safety level: Class C
  4. Electromagnetic compatibility level: E2
  5. Flow profile sensitivity level: U10 D5
  6. Pressure loss level : △ P25
  7. Maximum allowable error.
  First, the main technical performance
  1, working environment temperature: 0-50 ° C
  2, relative humidity: ≤ 85%
  3, the measured water temperature: cold water meter 0-50 ° C; hot water meter 0-90 ° C; pure water meter 0-35 ° C
  4. Working pressure: 0.02MPa~1MPa
  5. Technical parameters:
  accuracy class and flow range


Test method

 The inspection of the smart water meter is carried out according to the technical conditions of each manufacturer and GB/T778. Inspection items: visual inspection (including external dimensions, etc.), hydraulic test, indication error, flow measurement and accelerated wear test. The number of water meters to be tested is at least three, and it is necessary to increase the number of water meters to be tested, up to a maximum of 10.

packaging storage and transportation
Each smart water meter should have a separate small package and prevent collisions during transportation and handling. The water meter should be placed horizontally. The water meter is an instrument, and the outer packaging should have obvious "up" and "light" marks. The water meter should be stored in a dry place where the ambient temperature is 5-40 ° C and the air does not contain corrosive media.

Technical indicators

Power supply voltage: 3.6V lithium Battery
quiescent current: ≦ 10uA
indication error limit
  A, from the minimum flow (Qmin) to the low zone excluding the boundary flow (Qt): ± 5%
  B, from the demarcation flow (Qt) to including High section of intercept flow (Qs): ±2%
Rated working pressure: ≦1.6Mpa
Ambient temperature: (0.1∽+50) °C
Relative humidity: (30%∽95%) RH 12, pressure Loss: ≤0.063MPa
Flow profile sensitivity level: U10, D5
Climate and mechanical environment Safety level: Class B
Electromagnetic compatibility level: E1

Development direction

Remote transmission and automatic reading system technology is a direction of smart water meter development. The smart card type water meter pre-paid function “first pay and then use water” can not become the only restrictive means for water fee collection after the social civilization develops to a certain height. At the present stage of the developed countries, they are applied within the enterprise to measure the water-saving control rated plan indicators and actual water consumption. There are also internal colleges and universities to save water. In the dormitory dormitory rooms, the card water is also controlled by smart water meters. The use of smart water meters that directly pre-paid water for residents' water supply in the society does not advocate the use of water after the first charge. For them, this issue is related to the "human rights" issue to drinkers, who have no money, Drinking water is still their right to survive, so this measure is not implemented. Since the founding of the country, since the day when the households have water supply, power supply, and gas supply, the procedure of paying for the first use and post-payment has been implemented. Changing the water after paying first is itself a kind of resistance to the hearts of the residents. Moreover, power supply and gas supply still maintain the law of first-use and post-paid, the economy is developed, the living standards of residents are high, and people's ideological realm is also improved. The law of paying for water first will not cause social problems of water fee arrears. Therefore, social civilization has progressed, and this kind of prepaid measures is not an ideal measure. Therefore, the prepaid form of the smart card type water meter gradually turns to the direction of the remote transmission and automatic reading system.
  In addition, due to the use of the card-type water meter, in addition to the user's voluntary repair or re-purchase of the water recharge, the operation information of the water meter can be transmitted to the system information center, and the manager must arrive at the site where the water meter is installed to know the operation of the water meter. Happening. If the water meter is reversed and the recharged water is used up, the water meter cannot automatically close the valve, or even the user removes the water meter and directly uses water. Only the management personnel can reach the site where the water meter is installed. Therefore, during the use of various card-type water meters, the management department cannot keep track of the operation of the water meter. It must be equipped with certain personnel to regularly inspect the on-site revolving of the water meter. Otherwise, the failure of the water meter and the amount of water missing cannot be known. . Therefore, remote transmission and automatic reading system technology is a direction of the development of smart water meters.
  We have conducted surveys on the use of prepaid water meters in many industrialized countries, such as the United States, Germany, France, Italy, Australia, etc. They have many automatic meter reading systems for water meter intelligent data collection, with remote transmission, remote sensing, and collection. And the centralized collection of intelligent water meters is widely used in industrialized countries, especially in the United States, such as Texas, Virginia, Colorado, Wisconsin and so on. The intelligent water meter automatic reading function has been widely used in the enterprise to control the water consumption control rated plan indicators and actual water consumption. There are also colleges and universities to save water. The school dormitory dormitory also uses the intelligent water meter automatic reading system to control.

Design

Introduction

  Because of its fundamental change in the traditional method of meter reading, the smart water meter implements the charging mode of buying water for cards. On the basis of saving a lot of manpower, it also solves the water fee arrears that have long plagued the water supply industry, and will directly supply water. The industry brings huge economic benefits. Therefore, its implementability is increasingly optimistic. How to optimize the design of the water meter in terms of technology, performance and price will be the key to the problem.

  Component

  2.1 The base water meter of the communication
The basic water meter of the communication is to install the signaling device in the ordinary mechanical water meter to provide the metering signal to the electronic main control circuit of the water meter to realize automatic metering of water. The transmitting device of the water meter is composed of a small magnetic steel and a magnetic sensitive element in a certain positional relationship. When a measuring unit (generally 0.01 m3 or 0.1 m3) of water flows, the magnetic sensing element sends a pulse signal to the main The control circuit is used for counting. Commonly used magnetic sensing elements are two types of reed switches and Hall elements. The reed switch occupies a clear advantage in the battery-powered micro-power smart water meter due to its static zero-power performance, and the working life of the high-quality reed switch more than 1 million times can fully meet the life cycle of the water meter. The power consumption of Hall elements is generally at mA level, although new products with micro power consumption have emerged (such as Allegro's switched Hall element A3210, which has a static power consumption of only 1μA), but its price is relatively expensive.
  2.2 control valve
  The intelligent water meter controls the water inlet valve of the water meter through the main control circuit to achieve the purpose of controlling the user's water. Therefore, reliability should be the design point of the valve. In the early days of smart water meter design, solenoid valves should be said to be a common choice because of its simple structure and low power consumption. However, after repeated trials, its shortcomings are inevitably exposed. Briefly, first of all, the electromagnetic valve has poor seismic resistance, which is also the most deadly weakness. Secondly, the plastic parts in the solenoid valve are easily deformed and corroded in the long-term water immersion environment, thus affecting the switching performance of the valve. Therefore, the design trend of the electric valve came into being. Although, compared with the solenoid valve, its structure is more complicated and the power consumption is larger. However, under the premise of reliability, the electric valve should have more application prospects. Further adjustments are needed in the structure. The bistable electric valve is a design idea. The valve is designed to drive the electric valve by electromagnetic conduction to reduce energy consumption.
  2.3 main control circuit
  2.3.1 structure block diagram
  Figure 1
  2.3.2 CPU selection
  Smart water meter is a small battery-powered system, therefore, CPU selection should focus on low voltage, low power consumption, high load capacity. The overall advantages of Microchip's PIC family of microcontrollers are clear. And its unique reduced instruction set (RISC) structure and bus Harvard architecture can save half of the program code compared with similar single-chip microcomputers, and the instruction speed can be increased by about five times, so it is an ideal choice. From the perspective of cost performance, PIC16C57 and PIC16C62 are two good choices. They all have their own Watchdog timer. The former is 2K*12-bit EPROM, 80*8-bit RAM, 20 I/O ports; the latter has 2K. * 14-bit EPROM, 128 RAM, 20 I/O ports, and 7-level interrupts. Of course, the PIC16C57 is cheaper, but because of its non-disruptive function, it can only use the query mode in software design. Compared with the interrupt mode, it is less powerful in terms of power saving, but it has little effect.
  2.3.3 Data Memory
  The data memory is used to store various information about the water meter calculated and processed by the CPU, such as water purchase amount, water consumption, user code, and the like. ATMEL's 256*8-bit E2PROM general-purpose memory AT24LC01 is easy to use and very inexpensive, and can fully meet the requirements of use. Although there are many programmable monitoring and encryption memories that are superior in performance, they are not necessary in products such as smart water meters because the boards are sealed in the water meter and the data exchange between the CPU and the memory. There is no external interface, so it doesn't matter if the saw is stolen.
  2.3.4 Reading and writing of the
  IC card The IC card reading and writing module is the logical interface circuit of the main control circuit and the IC card. It should firstly realize the power supply to the IC card and meet the requirements of the non-powered plugging and unplugging. It may cause damage to the IC card or even damage the IC card. This can be achieved by both hardware and software. As shown in Figure 2, when the CPU detects the insertion of the IC card through the IC card detection switch of the IC card holder, the IC-PWR port emits a low level after a suitable delay (about 10ms), and the system is controlled by the low-power transistor 9012. +5V power supply cut-in, in the same way, in the software design, when the reading and writing of the IC card is completed, the IC-PWR port is issued with a high level in time, and the power supply of the IC card is cut off, so that the IC card is pulled out.
  In addition, all IC card interface parts should be added with clamp protection diodes. These diodes can make the voltage on each pin strictly control between -VD~VCC+VD (VD is the forward voltage drop of the diode, usually Around 0.6V). In this way, it is possible to suppress the transient overvoltage caused by the jitter of the edge of the line interference and the logic level change, and further protection measures for the IC card.
  Figure 2
  2.3.5 Switching Valve Control
  The switch of the water meter valve is realized by the CPU turning on the switch electrical circuit according to certain switching conditions. The design of the control of the on-off valve must master two points: First, control the switch on the software. The current output time of the valve circuit, that is, the loop conduction time, the time is too long, the battery consumes too much energy; the time is too short to reliably switch the valve. The second is to have a storage circuit for closing the valve on the hardware circuit. When the power supply is de-energized, the circuit can release the energy in time and close the valve.
  2.3.6 Low Voltage Detection
  Low voltage detection is a very important problem for the single-chip microcomputer system. It plays a role in ensuring reliable operation of the system and avoiding data errors. The same is true for the design of smart water meters. Specifically, when the system is powered down to a threshold voltage (the threshold voltage should be higher than the minimum operating voltage of the CPU), the signal is transmitted to the CPU through the corresponding voltage detection circuit, and the CPU resets the system in time. The voltage detector can be selected from Hetai's HT70 series, which has a low price and complete specifications.
  2.3.7 Displaying
  the information of the smart water meter (water storage, switching valve status, battery status, etc.) display can be completed by the serial liquid crystal module. The interface between the serial liquid crystal module and the CPU is simple, occupying only three interface lines of DATA, WR and CS. Compared with parallel LCD modules, it greatly saves CPU I/O port resources. In addition, in order to meet the requirements of low power consumption as much as possible, the LCD can be normally in a sleep state, and the card is awakened to display it.
  2.3.8 Pulse signal processing The pulse signal
  from the signal base water meter should be treated as "anti-jitter" in software design. Because in real life, we often encounter such a situation: when a certain amount of air enters the water pipe, the water is opened and the water pipe will vibrate instantaneously. If the position of the magnetic steel and the reed pipe is just at a critical state. , the pulse signal will be sent to the CPU continuously, so that the CPU can not count correctly. The corresponding measure is when the CPU receives a pulse signal and then delays it appropriately (the delay can be as long as the maximum suction time of the magnetic steel and the reed switch is less than the water meter overload flow). It is then checked whether the signal is still present, and if not, it is considered a false signal.
  2.3.9 Anti-attack module The
  anti-attack module is a protection circuit that is designed to cause malicious attacks on the bayonet by means of high voltage and static electricity. Like Beijing Qiqi Company, Fugen Company and other domestic manufacturers have molded products that can be provided, and the performance is relatively reliable.
  2.4 Card selection
  The IC card can be divided into three categories: ordinary memory card, logical encryption card and CPU card. The card serves as a carrier for transmitting information between the user and the water supply department. Moreover, as an electronic money, security is a primary consideration in addition to reliability.
  Ordinary memory card chips have no security logic. Designers generally consider data encryption by combining certain encryption algorithms and rolling storage. However, since ordinary memory card contents can be read directly by card reading devices, data can be read. It is arbitrarily falsified, and the actual data is very likely to be repeatedly compared and compared, so the security is poor and it is not recommended.
  The logical encryption card provides the logical hardware password comparison function of the circuit. Under normal circumstances, only the user password and the application area password can access the data in the application area of the card, and the password counter is set in the card. Once the number of incorrect passwords is entered, the password counter is set. The number of times, the card will be self-locking. However, the data is transmitted in the clear code on the I/O port of the card. If the data is obtained by the device "eavesdropping", the purpose of making the fake card can be achieved. The usual practice is to encrypt the important data on the card by using internationally accepted cryptographic algorithms such as DES and RSA as an effective means of anti-eavesdropping. The price of the logical encryption card is relatively low. If the charge of the smart water meter is not included in the "city card" system, then it will be a good choice. The Siemens SLE4442 contains 256*8-bit E2PROM data memory, 32*1-bit protected memory, and a programmable security code (PSC) logic that meets the requirements of water meter cards.
  The CPU card chip itself integrates a microprocessor and has its own on-chip operating system (COS). Compared with the logical encryption card, the main advantages of the CPU card are reflected in two aspects: First, the security mechanism is more strict, and its on-chip operating system (COS) can effectively manage the key and make the data in the card. Encryption calculation and comparison are carried out to identify each other the legality of the card, the cardholder and the card reading device. Secondly, there is strong flexibility in "one card multi-use", which can be compatible with several different applications at the same time. Card and system interoperability is controlled by software stored in the card and in the system. Especially the second point, for "one card" The meaning is unquestionable. However, the specific use of the card for water meters should also be determined, as the price of the CPU card is still high.
  2.5 Software Flow Chart
  Figure 3 is a software flow designed according to the query method:


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