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| The measurement principle of electromagnetic flowmeter is based on Faraday's law of electromagnetic induction. The measuring tube of the flowmeter is a non-magnetic alloy short tube lined with insulating material. Two electrodes are fixed on the measuring tube by passing through the tube wall along the diameter direction. The electrode tip is basically flush with the inner surface of the lining. When the excitation coil is excited by bidirectional square wave pulses, a working magnetic field with a magnetic flux density of B will be generated in the direction perpendicular to the axis of the measuring tube. At this point, if a fluid with a certain conductivity flows through the measuring tube, an electromotive force E will be induced by cutting the magnetic field lines. The electromotive force E is proportional to the product of the magnetic flux density B, the inner diameter d of the measuring tube, and the average flow velocity V. The electromotive force E (flow signal) is detected by the electrode and sent to the converter through a cable. After amplifying and processing the flow signal, the converter can display the fluid flow rate and output signals such as pulses and simulated currents for flow control and regulation. |
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| In Figure 1-1, when a conductive fluid flows through an insulated tube with an inner diameter of D (m) and a pair of measuring electrodes at an average flow velocity V (m/s), and the tube is in a uniform magnetic field with a magnetic induction intensity of B (T). So, an electromotive force (E) perpendicular to the magnetic field direction and flow direction will be induced on a pair of electrodes. According to the law of electromagnetic induction, it can be written as equation (1): |
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Circuit working principle diagram
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1. Shell 2. Lining 3. Excitation coil 4. Converter 5. Grounding screw 6. Electrode
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| 1. The instrument structure is simple, reliable, without movable parts, and has a long working life. |
| 2. There are no flow blocking components, and there is no pressure loss or fluid blockage. |
| 3. No mechanical inertia, fast response, good stability, can be applied to automatic detection and adjustment of programmable control systems. |
| 4. The measurement accuracy is not affected by the type of measured medium and its physical parameters such as temperature, viscosity, pressure, etc. |
| 5. A separately designed sealing component at the connection between the sensor and the meter head can prevent external moisture from entering the meter head and sensor through the connection. |
| 6. The excitation and electrode wires are both made of high-quality single core shielded wires, which can reduce interference, improve signal cleanliness, and thus enhance measurement accuracy. |
| 7. The measurement flow range is wide. |
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| name |
HHDS water meter type electromagnetic flowmeter |
| Nominal Diameter |
DN10-DN400 |
| structural form |
Integrated and split type (GPRS) |
| maximum flow velocity |
15m／s |
| Fluid conductivity |
≥5uS／cm |
| accuracy class |
Level 1.0 |
| lining material |
Polytetrafluoroethylene, chloroprene rubber, polyvinyl chloride, perfluoroalkoxy (F46) |
| rated pressure |
4.0Mpa、1.6Mpa、1.0Mpa |
| Maximum fluid temperature |
integrated type |
70℃ |
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Separated type |
PTFE lining |
100℃； 150 ℃ (special order required) |
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Chloroprene rubber lining |
80℃； 120 ℃ (special order required) |
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Polycarbonate lining |
80℃ |
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Perfluoroethylene propylene (F46) |
100℃； 150 ℃ (special order required) |
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Polyfluoroethylene (Fs) |
80℃ |
| Signal electrode and ground electrode materials |
316 |
| Sensor material |
Carbon steel, 304 stainless steel |
| Shell protection |
IP68 |
| output signal |
GPRS RS485 (Modbus protocol) |
| Display on monitor |
Instantaneous flow rate, flow velocity, percentage, empty pipe ratio, positive Reverse accumulation, alarm display, second timer, battery level indicator |
| power supply |
3.6V lithium battery |
| excitation method |
Low frequency pulse DC excitation |
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| Caliber (mm) |
Measurement range (m3/h) |
Caliber (mm) |
Measurement range (m3/h) |
| DN10 |
0.14 ～ 1.40 |
DN100 |
14.13 ～ 282.60 |
| DN15 |
0.32 ～ 6.36 |
DN125 |
22.08 ～ 441.56 |
| DN20 |
0.57 ～ 11.30 |
DN150 |
31.79 ～ 635.85 |
| DN25 |
0.88 ～ 17.66 |
DN200 |
56.52 ～1130.4 |
| DN32 |
1.45 ～ 28.94 |
DN250 |
88.31 ～1766.25 |
| DN40 |
2.26 ～ 45.22 |
DN300 |
127.17 ～2543.4 |
| DN50 |
3.35 ～ 70.65 |
DN350 |
173.09 ～3461.85 |
| DN65 |
5.97 ～ 119.40 |
DN400 |
226.08 ～4521.60 |
| DN80 |
9.04 ～ 180.86 |
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| 1. Schematic diagram |
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Note: The above dimensions are for reference only. If there are special selections, the value may vary
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2. Size chart
| Nominal diameter DN |
pressure rating |
Outer diameter of flange D |
Bolt hole center circle diameter K |
Bolt hole n-L |
Total length L |
Height H |
Reference weight kg |
| 10 |
PN40 |
90 |
60 |
4-φ14 |
200 |
190 |
10 |
| 15 |
PN40 |
95 |
65 |
4-φ14 |
200 |
190 |
10 |
| 20 |
PN40 |
105 |
75 |
4-φ14 |
200 |
190 |
10 |
| 25 |
PN40 |
110 |
85 |
4-φ14 |
200 |
200 |
10 |
| 32 |
PN40 |
140 |
100 |
4-φ18 |
200 |
205 |
11 |
| 40 |
PN40 |
150 |
110 |
4-φ18 |
200 |
215 |
12 |
| 50 |
PN40 |
165 |
125 |
4-φ18 |
200 |
220 |
15 |
| 65 |
PN16 |
185 |
145 |
4-φ18 |
200 |
240 |
16 |
| 80 |
PN16 |
200 |
160 |
8-φ18 |
200 |
255 |
18 |
| 100 |
PN16 |
220 |
180 |
8-φ18 |
250 |
270 |
20 |
| 125 |
PN16 |
250 |
210 |
8-φ18 |
250 |
300 |
25 |
| 150 |
PN16 |
285 |
240 |
8-φ22 |
300 |
330 |
30 |
| 200 |
PN16 |
340 |
295 |
12-φ24 |
350 |
390 |
45 |
| 250 |
PN16 |
405 |
355 |
12-φ26 |
450 |
450 |
65 |
| 300 |
PN16 |
460 |
410 |
12-φ28 |
500 |
500 |
79 |
| 350 |
PN16 |
520 |
470 |
16-φ30 |
550 |
520 |
95 |
| 400 |
PN16 |
580 |
525 |
16-φ32 |
600 |
635 |
140 |
| 1. All data in the above table are based solely on standard sensors |
| 2. Other pressure levels not listed may have different sizes |
| For sensors with smaller diameters, the size of the meter head may be larger than that of the sensor |
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Selection of lining
| lining material |
Main performance |
Maximum medium temperature |
Scope of Application |
| integrated type |
Separated type |
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| Polytetrafluoroethylene (F4) |
1. It is the most chemically stable plastic, capable of withstanding boiling hydrochloric acid, sulfuric acid, nitric acid, and aqua regia, as well as concentrated alkali and various organic solvents. Not resistant to corrosion from chlorine trifluoride, high-temperature chlorine trifluoride, high-speed liquid fluorine, liquid oxygen, and ozone. |
70℃ |
100 ℃, 150 ℃ (special order required) as above |
1. Strong corrosive media such as concentrated acid and alkali
2. Sanitary media
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| 2. The wear resistance is not as good as polyurethane rubber. |
| 3. Its ability to resist negative pressure is not as good as that of chloroprene rubber. |
| Perfluoroethylene propylene diene (F46) |
Ditto. |
| Polyfluoroethylene (Fs) |
The upper limit of applicable temperature is lower than that of polytetrafluoroethylene, but the cost is also lower |
80℃ |
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| Polychloroprene rubber |
1. It has excellent elasticity, high tensile strength, and good wear resistance |
80 ℃, 120 ℃ (special order required) |
Water, sewage, and wear-resistant slurry slurry |
| 2. Resistant to corrosion in general low concentration acid, alkali, and salt media, but not resistant to corrosion in oxidizing media |
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Selection of electrodes
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| electrode material |
Corrosion resistance and wear resistance |
| Stainless steel 0Cr18Ni12Mo2Ti |
Used for weakly corrosive media such as industrial water, domestic water, and sewage, suitable for industrial sectors such as petroleum, chemical, and steel, as well as municipal and environmental protection fields |
| Note: Due to the wide variety of media and the complex factors such as temperature, concentration, and flow rate that affect their corrosiveness, this table is for reference only. Users should make their own choices based on the actual situation, and if necessary, conduct corrosion resistance tests on the selected materials, such as hanging plate tests |
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| 1. General requirements |
| a、 For the convenience of installation, maintenance, and upkeep, sufficient space should be reserved around the flowmeter |
| b、 Avoid installing flow meters in places with large temperature changes or high temperature radiation from equipment |
| c、 Flow meters should be installed indoors. If installed outdoors, direct sunlight should be avoided and sun protection devices should be installed if necessary |
| d、 Avoid installing flow meters in environments containing corrosive gases |
| e、 Avoid installing flow meters in places with strong vibration sources and magnetic fields |
| 2. Process pipe requirements |
| a、 The inner diameter of the upstream and downstream process pipes and the inner diameter of the flow meter should meet the following requirements: 0.98DN ≤ D ≤ 1.05DN (DN: flow meter inner diameter; D: Inner diameter of process pipe |
| b、 The process pipe and flow meter should be concentric, with a coaxial deviation of no more than 0.05DN |
  
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| 2.1 Straight pipe section |
| The use of straight pipe sections can prevent the medium from generating eddy currents or distortions due to the influence of bent pipes, TT type tees, globe valves, and variable diameter pipes |
 
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| 3. Grounding |
The flowmeter must be grounded according to regulations to ensure reliable operation and prevent operators from receiving electric shock
| Figure (1) Metal pipes without inner wall coating or lining do not use grounding rings for grounding. |
| Figure (2) Metal pipes and insulated pipes with inner wall coating or lining are grounded using grounding rings. |
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| 1. Reminder |
| a. The wiring of the electromagnetic flow converter must be completed by professional technicians; |
| b. All wiring should be done after cutting off the power supply; Connect correctly and firmly according to the instructions; |
| c. Tighten the compression nut and end cap of the outlet sleeve to maintain a good seal of the converter; |
| d. Surge suppression devices should be installed on lines that are susceptible to lightning surges; |
| e. Before supplying power, all wiring should be checked again for accuracy and correctness. |
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| 2. Wiring terminals and labeling diagram of the integrated converter |
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3. Wiring terminals and labeling diagram of the split converter |
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| Important information about active and passive 4-20mA!!! |
The electromagnetic flowmeter is a 4-wire instrument that is different from the two-wire instrument's 4-20mA. The two-wire 4-20mA instrument requires an ammeter to be measured and an external 24V power supply to work properly. However, the electromagnetic flowmeter itself is a 4-wire 4-20mA instrument that already has a 24V power supply inside and does not require an external connection. It only needs to be connected to a simple ammeter. Without special customization instructions, our company's electromagnetic flow meters are all active 4-20mA and do not require an external 24V power supply, otherwise the instrument will be burned out.
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| ① Integrated electromagnetic flowmeter active 4-20mA output wiring (by default, the integrated electromagnetic flowmeter is active 4-20mA, and the user equipment ammeter cannot have power output) |
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② Passive 4-20mA output wiring of integrated electromagnetic flowmeter (Passive 4-20mA output of body electromagnetic flowmeter needs to be specified when ordering, otherwise it is active 4-20mA output) |
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| ③ Active 4-20mA output wiring of split electromagnetic flowmeter (split electromagnetic flowmeter does not require special customization and supports both active and passive 4-20mA) |
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④ Passive 4-20mA output wiring of split electromagnetic flowmeter (split electromagnetic flowmeter does not require special customization and supports both active and passive 4-20mA) |
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| ⑤ How does the user device determine whether active current output or passive current output is required? |
| a. Disconnect the 4-20mA connection wire between the electromagnetic flowmeter and the user equipment to ensure that the user equipment is in an open circuit state; |
| b. Measure whether the 4-20mA connection line of the user device has a voltage of around 24V using a digital multimeter voltage range; |
| c. If there is a voltage of around 24V, passive current output is required; otherwise, active current output is required. |
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| a. Do not lift the flowmeter through the integrated converter housing |
| b. Do not use metal suspension chains |
c. Please use leather straps to lift the flowmeter
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| Fault Name |
solution |
| Converter has no display |
1. Check if the power supply is connected |
| 2. Check if the fuse is intact |
| 3. Check if the power supply voltage meets the requirements |
| If all three of the above are normal, the converter will be returned to the factory for repair |
| Excitation alarm |
1. The insulation degree of the excitation coil decreases |
| air traffic control alarm |
1. Whether the tested fluid is full in the pipe |
| 2. Whether the flowmeter is installed correctly as required |
| 3. The conductivity of the tested fluid is too low |
| 4. The air traffic control threshold is set too low |
| Display traffic when there is no traffic |
1. The air traffic control threshold is set too high |
| 2. Air traffic control alarm allowed not to be turned on |
| 3. The electrode is contaminated, causing a zero offset (at this time, the pipeline is full) |
| 4. The insulation degree of the signal line decreases (at this time, the pipeline is full) |
| Flow measurement is inaccurate or fluctuates greatly |
1. Is the fluid filled in the pipe |
| 2. Is the flowmeter grounded according to regulations |
| 3. The insulation degree of the signal line decreases |
| 4. Whether the flowmeter is installed correctly as required |
| Traffic limit alarm |
1. If the on-site traffic exceeds the traffic limit threshold, modify the traffic limit threshold |
| Flow lower limit alarm |
1. If the on-site traffic is below the lower limit threshold, modify the lower limit threshold of the traffic |
| No traffic display when there is traffic |
1. Is the shut-off valve open |
| 2. Signal line grounding |
| 3. Low traffic, high small signal cutoff setting |
| 4. The air traffic control threshold is set too low |
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