An electromagnetic water meter is also a kind of electromagnetic flowmeter. Due to the diverse media measured by electromagnetic flow meters, there is a wide range of electromagnetic flowmeter on the market.
Electromagnetic flowmeter measurements of the media requirements are conductive and have a specific dielectric constant. Although, due to the different market positioning and use requirements, there are significant differences between the two, this paper makes the following comments.
1. Application
Electromagnetic flowmeter is widely used, suitable for industrial production of various conductive media flow continuous measurement and production process control field, scientific research in the field of measurement and control.
Electromagnetic water meter to measure clear water, raw water is the main. It is widely used in the municipal field to solve the water source and urban and rural water supply measurement, statistics, analysis, and settlement function.
2. Accuracy
The accuracy of electromagnetic flowmeter is usually ± 0.5%, high precision can reach ± 0.2%, ± 0.3%.
The accuracy of the electromagnetic water meter is usually level II (Q2 to Q4 ± 2%, Q1 to Q2 ± 5%). However, high precision can reach the I level (Q2 ~ Q4 ± 1%, Q1 ~ Q2 ± 3%).
3. Size
Most manufacturers of electromagnetic flowmeters can offer products from DN20 to DX500. In addition, more prominent professional manufacturers can provide DN10 ~ DX3000 electromagnetic flowmeter and DN25 ~ DN600 specifications for many applications.
In the current market, electromagnetic water meter caliber in DN50 ~ DM300, a few advanced multinational professional manufacturers can produce DN25 ~ DM300 caliber full range of electromagnetic water meters.
4. Repeatability
4.1 Electromagnetic flowmeter
Repeatability is one of the necessary technical indicators. For example, 0.5 level of accuracy of electromagnetic flowmeter. Its repeatability should be better than ± 0.16%: 0.2 level table repeatability should be better than ± 0.06%.
4.2 Electromagnetic water meter
An electromagnetic water meter does not affect repeatability as an assessment of quality indicators. It is only a design and experimental hand.
Electromagnetic water meters are critical technical indicators for accuracy, low starting flow, Q1 flow point, and range ratio (Q3/Q1). Of course, for the flowmeter, both can ensure the long-term continuous and stable operation is essential.
5. Power Supply Method (Power Consumption)
5.1 Electromagnetic Flow Meter Power Supply
The electromagnetic flowmeter processing rate has high accuracy, and control requirements are fast, stable, and accurate.
Because of the electromagnetic flowmeter and the outside world information exchange method complex (output 4 ~ 20mA current signal, 0 ~ 10KC frequency signal, RS-485 communication, switch control, etc.). Because of its high degree of isolation, and thus the electronic circuit with a large number of high-speed electronic components, power consumption up to 15 ~ 25 V-A.
It must be powered by the mains (AC220 V) and a dedicated external power supply (DC24 V). Therefore, anti-interference, photoelectric isolation, electromagnetic isolation, and other technical measures to prevent the solid electromagnetic shock of the power supply are very necessary.
5.2 Power Consumption of Electromagnetic Water Meters
The sampling rate of the electromagnetic water meter is relatively slow. It is because advanced low-power, ultra-low-power integrated circuits dominate their electronic circuit.
The calculation method is a unique, high-efficiency power-saving method. Thus the power consumption is deficient and can be continuously powered by the internal battery for a long time.
It requires a battery operating life of at least 5 to 6 years for electromagnetic water meters, and now there are also products with 8 to 10 years. Therefore, reducing power consumption and increasing the battery’s operating life is a difficult challenge for electromagnetic water meters.
6. Sampling Rate
Electromagnetic flowmeter measurement of real-time to meet the process requirements of industrial control. Its characteristics are accurate and high-speed. Thus, the sampling rate is generally required to be higher than 100 ns once.
The electromagnetic water meter sampling rate is 1 ~ 30 s / times. Usually, the sampling rate is 15 s / times, and the internal battery guarantees continuous measurement for six years.
7. Instrument Communication
7.1 Electromagnetic flow meters
Electromagnetic flow meters have a wide range of metering and flow control methods. Therefore, communication methods are relatively wealthy. The general manufacturers have the following configuration.
7.1.1 Quantitative pulse output.
Such as the output of a pulse represents 1m3 / h flow (optional 0.1m3 / h, can also choose 0.01m3 / h).
7.1.2 Frequency output.
Outputs 0 to 10 kHz, representing a frequency range of 0 to Qmax flow.
7.1.3 Output signal. (4 to 20 mA current)
Electromagnetic flowmeter usually indicates the instantaneous amount of Qmin ~ Qmax. 4 ~ 20 nA current analog signal designed in recent years can be simultaneously digital communication. HART (protocol) communication is also possible.
7.1.4 RS-485 communication.
Electromagnetic flowmeters usually implement the Modbus RTU communication standard.
7.1.5 Switching output.
Electromagnetic flowmeter generally has 1 to 2 output control to perform the upper limit of overflow shutdown, overflow lower limit open gate, and other process control.
These communications are almost always connected to the meter, computer, and control equipment through the cable to ensure accurate, real-time, reliable metering and process control.
7.2 Electromagnetic Water Meters
Electromagnetic water meters are mainly used in raw and residential tap water metering, statistics, analysis, and settlement. It has few process control requirements, and its internal battery supply limits it from consuming too much power.
As a result, its communication methods are relatively simple, and manufacturers generally choose to communicate in several configurations, as described below.
7.2.1 Data Display.
Electromagnetic water meters, like traditional cold water meters, can be manually read and therefore have LCD screens for flow data display.
7.2.2 Switching Output.
7.2.3 Device interface
The interface between the electromagnetic water meter and the wireless communication device allows for networked communication via wireless communication devices.
7.2.4 Communication Signal.
The RS-485 communication of the electromagnetic water meter is the same as that of the electromagnetic flowmeter. The electromagnetic water meter usually implements the Modbus RTU communication protocol. It requires an external power supply (DC24 V), which often requires four cables.
Electromagnetic water meters can use micro-power technology for RS-485 communication, which can be powered by an internal lithium battery, eliminating the need for two cables for the external power supply and requiring only two cable connections for communication.
7.2.5 Infrared Communication.
It is a wireless two-way communication method with low power consumption. It meets the demanding protection requirements of electromagnetic water meters installed downhole and in water.
8. Operating Environment
8.1 Temperature Requirements
Electromagnetic flowmeters used on a wide range of occasions, usually in a 20 ~ 55 ℃ temperature environment, can be continuous, regular, reliable work. Even at 70 ℃, high-temperature conditions can be a joint operation in some areas.
Electromagnetic water meters generally can only be in a 0.1 ~ 55 ℃ temperature environment. Therefore, continuous work, design, and performance testing need to consider the high temperature of the direct summer baking scene.
8.2 Maintenance Requirements
Electromagnetic flowmeters are usually by professional maintenance and maintenance and often have a cycle (about one year) of testing and maintenance.
The electromagnetic water meter testing cycle is longer (about two years), usually almost in a state of non-supervision, with large diameter meter data values on the measurement and settlement of the enormous impact. Thus its design, testing, and manufacturing quality requirements are higher.
9. Protection requirements
9.1 Protection requirements for electromagnetic flow meters
9.1.1 Use of the environment
Electromagnetic flowmeter operation of the environment is complex. Therefore, manufacturers use different environmental designs and different protection methods for users.
9.1.2 Operating conditions
Such as the use of IP66 standard general-purpose electromagnetic flowmeter. It can only protect against rainwater drenching. When we use it in a high temperature and high humidity environment, we have to use a particular sealing high-temperature resistant design.
9.1.3 Use occasions
Submersible electromagnetic flowmeters are designed with protective housings according to IP68. Certain dangerous events (such as textile mills, flour processing plants, chemical plants, coal mines, and flammable and explosive places) use electromagnetic flowmeter; it must be designed by the explosion-proof standard to protect the shell. So electromagnetic flowmeter manufacturers will usually use the user’s environmental conditions to provide the appropriate protection mode products.
9.2 Electromagnetic water meter protection requirements
9.2.1 Use of the environment
The electromagnetic water meter measures a relatively single medium. It is mainly clean raw water (such as water from rivers, lakes, and lakes, healthy water, and groundwater) and clean tap water supplied by the municipality.
9.2.2 Occasions for use
There is almost no dangerous or explosive dust in electromagnetic water meters, and the temperature difference between the use of the environment is not too big. Hence, its protection requirements seem relatively easy to solve.
The electromagnetic water meter is often installed in wet places and downhole. The pipeline leakage and rain and snow can soak the electromagnetic water meter in water. So it is crucial to prevent water leakage at the electromagnetic water meter housing seal and the communication cable inlet.
9.2.3 Protection level
Electromagnetic water meters are protected by a submersible housing design, improving the protection quality. However, electromagnetic water meters must meet the test requirements of 1 m water depth and seven days and the IP68 standard of 2 m water depth and more than ten days.
Electromagnetic water meter housings are currently manufactured to the IP68 standard for 2m water depth and 30 days. Consideration is being given to increasing the protection test requirements to 10m water depth and 30 days to achieve a protection life of 6 years or more.