Mine sewage flow meter scale of the circuit design and measurement analysis

Abstract: the design of mine sewage flow meter scale circuit analysis and measurement of information produced by excellent flow meter, flow meter manufacturer to offer you the quotation. 0 introduction in recent years in the field of industrial sewage flowmeter has rapid application, especially in terms of water and sewage flow measurement is particularly outstanding, due to its flexible measurement and high sensitivity, industry, mineral water measure all kinds of water. More flow meter manufacturers choose model price quote you are welcome to inquire, here is mine sewage flow meter scale circuit design and measurement analysis for details. 0 introduction in recent years in the field of industrial sewage flowmeter has rapid application, especially in terms of water and sewage flow measurement is particularly outstanding, due to its flexible measurement and high sensitivity, industrial water measure all kinds of water, such as pulp flow medium. However, due to the special requirements of coal mine safety, very little wastewater flow meter can be used in the coal mine, such as, can not meet the requirement of the mining flameproof and intrinsically safe, narrow measuring range and the transmission signal is vulnerable to external magnetic field interference, etc. To solve these problems, developed a suitable for mining flow of sewage flow meter circuit. It USES a new type of single chip microcomputer to control, combined with the special in the excitation circuit, has many functions such as real-time detection and display in time, after trial companies, performance and technical indicators have reached advanced level of similar products at home and abroad. 1 design scheme 1. 1 design at present, our country the safety of the mine explosion-proof electrical products types are mainly composed of flameproof and intrinsically safe. In the design of each part is to strictly control circuit electric spark energy, so special in the excitation circuit is adopted in design to prevent field current cause electric spark; Using new low-power microcontroller to control the work of the entire device, to ensure its stability and reliability; Use a variety of electromagnetic shielding measures to prevent electrostatic and electromagnetic interference, to ensure the stability of the circuit. 1. System hardware circuit part 2 ( 1) Block device adopts high speed single chip microcomputer module circuit, STM32F407） , it has a floating point operation ability, low power consumption, power consumption is only 38. 6mA。 Used to control the sewage flow meter, including produce square wave excitation pulse signal, the receiving reflect the size of the flow from the sensor output voltage signal, 4 ~ 20 mA current signal for analog display instrument, CPU module with all kinds of RS232 interface circuit, high speed USB interface, etc. ) , keyboard and display interface circuit, etc. Block diagram is shown in figure 1. （ 2) Sensors in order to ensure the accuracy of measurement, the requirements of the sensor probe into a streamlined, when the probe insert will have little impact on the fluid, are regarded as approximate shine flow state. The concrete with 25. 4 mm stainless steel tube as the probe shell, using soft magnetic core, excitation coil of core wire bag, seal it after around a streamlined hemisphere high strength plastic shell, it has a pair of stainless steel electrode, connected to the excitation coil. In order to avoid the probe induced emission signals caused by interference, the signal transmitting wire, coil with shielding electrode wire processing. （ 3) Special circuit design (1) excitation signal and the driving circuit in order to ensure that the probe work in open flow state, try to probe size is small, so the excitation current is small, for subsequent the input impedance of the receiving circuit has a high enough to ensure that the sensor's sensitivity and anti-interference; In order to prevent the power frequency interference of ac 50 Hz, square wave current is chosen as the excitation current, the frequency can choose a quarter of the work frequency of 12. 5 Hz, effectively restrain power frequency interference. Excitation signal generated by single chip microcomputer internal, output 12 from 26 feet. Received IC5 (5 Hz square-wave signal, LMD18200T) 3 feet signal, it is a field coil driver module circuit, internal driven by H bridge, sends out the field current to the excitation coil between the 2 feet and 10 feet. In excitation coil L 20 ~ 30 mA is formed on the positive and negative symmetrical square wave current, it with the square wave voltage synchronous control. Fluid motion cutting lines of magnetic force produced by square wave voltage and exciting current completely in sync, with square wave voltage synchronized control switch network, facilitate synchronous signal demodulation in the receiving circuit. Circuit shown in figure 2. Type (2) in the excitation coil excitation current in the circuit sensor is the spark of hazards, the sewage flow meter to be used for mine, ensure the excitation circuit meet the essential safety requirements. When current flows through the excitation coil, inside the coil creates a magnetic field, magnetic field energy storage, when circuit disconnection, the energy stored in the coil will be released in the form of a spark, so you must discharge coil in the storage can to reach the requirement of the Ann. Used on both ends of the coil in parallel a bidirectional diode ( TVS diode P6KE6. 8CA） As stream branch to discharge coil magnetic energy storage, reduce the electric spark when on and off, absorption current, discharge energy. In order to achieve the purpose of the intrinsically safe. (3) sensor amplifier circuit circuit is shown in figure 3. IC2 ( SL28617） Preamplifier is used for amplifying reflect the flow of voltage signals from sensors, Rin and Rfb resistance to change the picture size, can change the gain of the operational amplifier.
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