Measurement principle of electromagnetic water meter and electromagnetic flowmeter:
The law of Faraday electromagnetic induction: The conductor is cut into the magnetic force line vertically, and the induction electromotive force (induction voltage) is generated at both ends of the conductor.
From this we can see that the electromagnetic water meter measured the surface information of the cross -section of the entire pipe diameter, which was greatly enhanced. As the electrode produces oxide, the electromagnetic water meter and flowmeter will be more stable. Water departments often use large -caliber electromagnetic flowmeters to run continuously for more than ten years without maintenance. This is also the long -term foundation of Waterfront customers' trust in electromagnetic water meters.
So how to choose an electromagnetic water meter or electromagnetic flowmeter meter? Let's briefly introduce the following editors:
1. In terms of use:
Electromagnetic flowmeters are widely used. It is mainly suitable for the continuous measurement of various conductive medium in industrial production and the field of production and control in production process control and scientific research.
The electromagnetic water meter is mainly measured water and raw water. It is widely used in the municipal field, and it mainly solves the function, statistics, analysis, and settlement functions of water supply and urban and rural water supply.
2. accuracy
The accuracy of electromagnetic flow meter is usually ± 0.5%, which can provide ± 0.2%and ± 0.3%of products.
The accuracy of the electromagnetic water meter is generally II (Q2 ~ Q4 ± 2%, Q1 ~ Q2 ± 5%), and can provide level 1 products (Q2 ~ Q4 ± 1%, Q1 ~ Q2 ± 3%).
3. Activity
Most of the manufacturers of electromagnetic flowmeters can provide products with DN20 ~ DN500. Large -scale professional manufacturers can provide electromagnetic flowmeters of DN10 ~ DN3000; DN25 ~ DN600 specifications have more than Z.
The market sales of more than the electromagnetic water meter in the market are in DN40 ~ DN300. A small number of advanced multinational professional manufacturers can produce a full range of electromagnetic water meters with DN25 ~ DN800 caliber.
Pipe segmentation electromagnetic flow meter
4. The range range (metering velocity range)
The medium flow rate measurement range of the electromagnetic flowmeter is 0.3m/s ~ 12m/s,
The high measurement flow rate of the electromagnetic water meter can reach about 15m/s. Generally, the flow point of the electromagnetic water meter is selected at 12.5 ~ 13.5m/s flow rate. The range of electromagnetic water meters refers to the standard of cold water meter, which is a standard for enforcement. As we all know, the flow range of cold water meters can be expressed by Q1 (small traffic), Q2 (dividing traffic), Q3 (commonly used flow), Q4 (z to large flow). Generally, its flow measurement characteristics can be compared with Q3/Q1 from Q3/Q1. (R value), q4/q3 = 1.25, q2/q1 = 1.6 to reflect. At present, the electromagnetic water meter of advanced professional manufacturers can reach 400 Q3/Q1. For the accuracy of the general electromagnetic water meter, users can choose level 1 (Q2 ~ Q4 ± 1%, Q1 ~ Q2 ± 3%) and II (Q2 ~ Q4 ± 2%, Q1 ~ Q2 ± 5%). Improving the measurement sensitivity of the electromagnetic water meter (that is, reducing the Q1 flow point) is the direction of the electromagnetic water meter. Electromagnetic water meter, the starting flow of the starting movement is usually 1/4 ~ 1/10 of the small traffic (Q1 flow point). The electromagnetic flowmeter does not have the concept of starting flow.
5. Repeatability
Repeatability is an important quality indicator of various flow instruments. For electromagnetic flowmeters, its repetitive indicators are 1/3 of accuracy. For example, the electromagnetic flowmeter at 0.5 -level accuracy shall be better than that of 0.16%; the repetitiveness of the 0.2 tables should be better than that of the soil 0.06%. As an electromagnetic flow meter, its important technical indicators are accuracy, repetitive, fast sampling and range ratio.
Electromagnetic water meters do not take duplicability as a quality indicator of an assessment, it is only a design and experimental indicator. The important technical indicators of the electromagnetic water meter Z are accuracy, low starting flow, Q1 flow point and range ratio ratio (Q3/Q1). Of course, for traffic meters, both can ensure that long -term continuous stable operation is very important.
6. Power supply method (power consumption)
Generally, the processing rate of electromagnetic flowmeters is fast, high -processing accuracy, and control requirements are fast, stable and accurate. Due to the complexity of electromagnetic flowmeter and external information communication methods (output 4 ~ 20mA current signals, 0 ~ 10kc frequency signals, RS-485 communication, switch volume control, etc.), high degree of isolation Consumption can reach 15 ~ 25VA, which must be supplied by the Municipal Electric (AC220V) and the special external power supply (DC24V). As a result, technical measures such as anti -interference, photoelectric isolation, and electromagnetic isolation are necessary to prevent strong electromagnetic shocks from power supply.
The electronic circuit of the electromagnetic water meter is dominated by the extremely advanced low -power or ultra -low power consumption integration circuit. The calculation method is a special efficient power -saving method. Therefore, the power consumption is extremely low. It can be powered by internal batteries for a long time. In this way, the battery life of the electromagnetic water meter requires at least 5-6 years. For electromagnetic water meters, reducing power consumption and increased battery life is a difficult challenge.
7. Pipeline structure and measurement direct pipe section
The electromagnetic flowmeter can be fully powered by the municipal power. Therefore, the choice of electronic components and electronic lines is less affected by power consumption and a wide range of choices; hundreds of millilites of excitation current make the signal output amplitude of the sensor is also large, so there is no need to confront the current flow. , Terminal acceleration to enhance the signal amplitude. The measuring cavity of electromagnetic flowmeters is direct tube, simple process, low processing cost, and is a common design method for the measurement of electromagnetic flowmeter measuring cavity. The direct tube structure will hardly cause the disorder of the measured streaming field. The measured flow rate is basically the economic flow rate (Z, the high current speed is less than 8m/s), and the high -speed sampling rate can be corrected in time. Therefore, the direct pipe section of the electromagnetic flow meter is the front 5D and the rear 3D to meet the measurement accuracy requirements.
The electromagnetic water meter is powered by the lithium battery in the interior to reduce the power consumption and increase the working life is the key to its design tasks. Therefore, it can only use a lower excitation current (usually its excitation current is only about one -tenth of the electromagnetic flow meter, or even Lower), the valid output signal value of the sensor is very weak. Electromagnetic water meter R & D personnel usually use two methods to enhance signals: to increase the magnification of the signal: the second is to reduce the measurement section to reduce the medium flow rate, which will greatly increase the flow signal. Therefore, the measuring cavity of the electromagnetic water meter almost uses the shrinkage process. Generally, the shrinkage diameter is about 70%to 80%of the original a caliber. For design principles. The reduction of the diameter of the electromagnetic water meter has a certain rectification effect. Under certain circumstances, it can be installed directly before and after.
8. Communication method:
The electromagnetic flowmeter is: the standard output signal is pulse frequency output, the output available for options is 4 ~ 20mA, isolation or non-isolation RS485/RS232C digital communication interface, and supports on-site bus communication methods such as Modbus, Profibus-DP and Hart;
The electromagnetic water meter is mainly divided into:
Wired communication: RS-485
Wireless communications: 4G, NB-IoT
9. Temperature requirements:
Electromagnetic flowmeters and electromagnetic water meters are usually required to work continuously, stable and reliable in the temperature environment of -20 ° C to 55 ° C. Some specific fields can even run normally under high temperature conditions at 70 ° C. The standards of cold water meters performed by electromagnetic water meters are usually T30 and T50.
