I. Overview of urban sewage flow meter consists of two parts, the sensor and converter. It is based on the work of Faraday's law of electromagnetic induction, used to measure the conductivity is greater than 5μS / cm conductive liquid volumetric flow rate, is a measure of the volume flow of conductive medium for induction meter. In addition to measure the volume flow of conductive liquid, it can also be used to measure the volume of a homogeneous liquid-solid two-phase flow of a liquid suspension of acid and alkali and other strong corrosive liquids and slurries, pulp and paper pulp. Widely used in flow measurement of petroleum, chemical, metallurgy, textile, paper, environmental protection, food and other industrial and municipal administration, water conservancy construction, river dredging and other fields. Second, the principle according to Faraday's principle of electromagnetic induction in the measuring tube axis and the magnetic field lines perpendicular to the wall to install a pair of sensing electrodes, when the conductive liquid tube axis of movement along the measurement of conductive liquid cutting magnetic field lines generated EMF, this induction potential detected by the two detection electrodes, the numerical size and flow proportional to its value: E = KBVD formula: E- EMF; K- and magnetic field distribution and the axial length of the relevant factors; B- magnetic induction; V - the average velocity of a conductive liquid; D- electrode spacing; (measuring tube diameter) E EMF sensor as traffic signals, transmitted to the converter, amplified, filtered transformed by a series of digital processing, with a backlit dot matrix LCD instantaneous flow rate and cumulative flow. The converter has 4 ~ 20mA output, alarm output and frequency output, and features such as RS-485 communication interface, and supports HART and MODBUS protocol. Third, the instrument features ■ full digital processing, anti-interference ability, reliable measurement, high accuracy flow measurement range up to 150: 1; ■ Ultra-low EMI switching power supply for power supply voltage range, anti-EMI performance; ■ 16-bit embedded microprocessors, computing speed, high precision, programmable low-frequency square wave excitation frequency and improve the stability of the flow measurement, low power consumption; ■ using SMD devices and surface mount (SMT) technology, circuit reliability high; no moving parts inside ■ pipes, unimpeded flow of parts, measuring almost no additional pressure loss; ■ at the scene according to the actual needs of users online range; ■ measurements and velocity distribution, fluid pressure, temperature, density, viscosity and other physical parameters; ■ High-resolution backlit LCD display, full Chinese menu, easy to use, simple to operate, easy to learn; ■ has RS485, RS232, Hart, and Modbus and other digital communication signal output; (optional) ■ with self checking and self-diagnostic function; total ■ hour meter record function, in hours of total traffic records for hourly metering system (optional); ■ has three internal totalizer can show a positive cumulative amount of anti- and the cumulative amount of the difference between the volume totalizer, the internal clock has not power down, can record 16 power-down times. (Optional); ■ infrared handheld operator, 115KHZ communication speed, long-distance non-contact operation of all functions of the converter (optional). Table 1 Nominal Diameter (mm) (special specifications can be customized) pipeline tetrafluoroethylene lining: DN10 ~ DN600 pipeline rubber lining: DN40 ~ DN2200 flow direction of positive and negative net flow turndown ratio 150: The value of a measurement repeatability error ± 0.1% accuracy class Pipeline: 0.5, 1.0 measured medium temperature ordinary rubber lining: -20 ~ + 60 ℃ high temperature rubber lining: -20 ~ + 90 ℃ PTFE lining: -30 ~ + 100 ℃ high temperature four fluorine lining: -20 ~ + 180 ℃ rated working pressure (hypertension can be customized) DN10-DN150: ≤1.6MPa DN200-DN350: ≤1.0MPa DN400-DN1000: ≤0.6MPa DN450-DN2200: ≤0.25MPa flow rate range 0.1-15m / s conductivity range measured fluid conductivity ≥5μs / cm signal output 4 ~ 20mA (load resistance 0 ~ 750Ω), pulse / frequency control level communication output RS485, MODBUS protocol, HART protocol Power supply AC220V or DC24V require straight pipe length upstream ≥5DN, downstream ≥2DN connections are made between the meter and piping flange connection, flange meet the national standard: GB / T9115.1-2000 ExdeiallBT4-T6 Explosion levels of protection IP65, IP68 special order up Ambient temperature -25 ~ + 60 ℃ Relative humidity 5% to 95% of the total power consumption of less than 20W 3. Select the electrode material should be based on the measured fluid corrosive to select the material of the electrodes, check the manual for special fluids should be corrosion Test material code corrosion resistance of 316L stainless steel V 1 applies to a neutral solution of industrial, domestic water, raw water wells, two municipal sewage and other weak corrosive acids, bases, salts medium such as carbonic acid, acetic acid, Hastelloy C HC 1 applies in resistance to oxidizing acid, such as corrosion nitric acid, mixed acid, a mixture of chromic acid and sulfuric acid salts of 2 in oxidation resistance or other oxidants such as environmental Fe, Cu 3 sea water, alkali solution, a solution of the oxide has an excellent corrosion resistance 4 NA: hydrochloric Hastelloy B HB 1 for non-oxidizing acids, bases, salts such as sulfuric acid, phosphoric acid, hydrofluoric acid has good corrosion 2 NA: Ti titanium nitrate resistant to water, suddenly all kinds of hypochlorous acid chlorides and a variety of corrosive salt hydroxide Ta Ta except hydrofluoric acid, almost all corrosive chemical media capability. But expensive platinum (Pt) All applicable chemical salt solution (fuming sulfuric acid and nitric acid) Tungsten W has excellent wear resistance, dedicated to the mud, pulp and other abrasive media 4. lining material selection should be based on measured media corrosive wear and temperature to select the lining material lining material corrosion resistance operating temperature range Ne-resistant neoprene generally low concentrations of acid salt corrosion -20 ~ 70 ℃ lower industrial water effluent pH and salt concentration of urethane rubber PO has excellent wear resistance, abrasion serous dedicated to strong, not a liquid containing solid particles decay -10 ~ 60 ℃ (grout slurry, etc.) poly FEP FEP 1 and corrosion resistant PTFE quite 2 high mechanical strength, good wear resistance within 3 table smooth, easy adhesion precipitate 4 has good resistance to negative, anti-vacuum effect -40 ~ 180 ℃ all fluids except for mortar and other strong abrasive media. Like with PTFE, Teflon PTFE can be used in beverages and other media have health requirements can resist almost all corrosive chemical media, poor wear resistance -40 ~ 180 ℃ can not be used to vacuum pipes and wear resistance strong fluid