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Each metering pump fluid pump determines the amount of its measurement capacity. In a certain effective diaphragm area, the metering pump output fluid volume flow proportional to the stroke length L and stroke frequency F: VαA * F * L Metering pump in the medium and work pressure to determine the circumstances, by adjusting the stroke length L and stroke frequency F can be achieved on the metering pump output of the two-dimensional adjustment. Although both stroke length and frequency can be used as a control variable, metering pumps generally regard stroke length as a coarse variable in engineering applications and stroke frequency as a fine-tuned variable: adjust the stroke length to a certain value and fine-tune it by changing its frequency , Increase the flexibility of regulation. In relatively simple applications, the stroke length can also be set manually, using only the stroke frequency as a control variable, simplifying the system configuration. Metering pump conventional analog / switch signal conditioning 0 / 4-20mA analog current signal is widely used in process control applications as the standard for signal exchange between sensors, controllers and actuators. The metering pump with external control function is also mainly used in this way, to achieve the stroke frequency and stroke frequency External adjustment. Metering pumps Position servos are the most common way to adjust stroke length. The integrated servos are designed to accept 0 / 4-20mA control signals directly from the regulator or computer, thus automatically adjusting the stroke length to vary from 0-100%. Relatively speaking, there are quite a few ways to realize the stroke frequency adjustment, mainly including inverter motor control and direct relay contact control. Driven by a 0 / 4-20mA current signal, the variable frequency drive operates the metering pump motor at the desired speed to adjust the stroke frequency. For solenoid driven and partially motor driven metering pumps, the external contact signal can also be used to adjust the stroke frequency. Metering pump base control In some special occasions, such as pH adjustment, metering pump as an actuator, add acid or base under the control of the regulator. To simplify system configuration and improve reliability, a microprocessor-based embedded control system is integrated directly into the dosing pump so that only a pH sensor is required to provide a complete conditioning system. The concept of a base smart metering pump is also suitable for controlling other process parameters such as ORP and residual chlorine concentration. Metering pump set program-controlled Due to the internal integration of the microprocessor, some metering pump products have been greatly enhanced in the control performance and operation performance. In addition to the real-time metering and flow adjustment by external control commands, they also have the functions of quantitative addition, time-series triggering program addition, event sequence Triggering program addition, time-event hybrid triggering program addition and automatic calibration and other modes of operation, and can provide to pump the total amount of fluid, the number of remaining strokes and to be transported fluid capacity, set the stroke length and other related measurement Pump working parameters and other useful information. The time sequence triggers the program work mode so that the metering pump is based on the real time clock completely according to the pre-planned task list. The metering pump can quantitatively add the working medium according to the set number of strokes or time at a specified time. The time can be expressed in hourly, , On weekdays, one week and two weeks for the cycle of flexible set; and event sequence triggered program-based work so that the metering pump based entirely on real-time trigger event, according to pre-planned task list, at a specific event (contact input) by setting The number of fixed stroke or time to add the working medium. The above two methods can be mixed organically to complete the more complex time-event hybrid triggering mode of operation. Up to 81 events can be set. A simple example is a cooling tower circulating water disinfection and algae removal system. Disinfectant to a specific concentration according to the proportion of added water flow to add; and process requirements, in the process of adding the proportion, the metering pump should also be a large number of pulses per week to add a disinfectant (such as set at Friday 12-13) And asked to pause at this time to add a role. The whole programming is very simple, so complex and fluid addition tasks can be easily and accurately achieved. Fieldbus ProFibus control Metering pump In the petrochemical industry and other large-scale high degree of automation applications, the use of digital communications protocols for high-speed transmission of data between automation equipment and then form a networked control system, large capacity, high reliability, has become the mainstream of development. After being incorporated into the German DIN standard in the early 1990s, the fieldbus ProFibus became the European standard (EN50170) again in the late nineties and has been widely adopted worldwide. It has become one of the representative protocols in fieldbus technology . Fieldbus ProFibus consists of three situations. ProFibus-DP, ProFibus-PA and ProFibus-FMS. Which ProFibus-DP (DecentralizedPeriphery) is defined as a decentralized peripheral fieldbus, metering pump designed specifically for the process control system and decentralized peripherals, high-speed data exchange and design. The transmission medium is twisted pair or fiber optic connection RS485 transmission standard, baud rate 9.6-12Mb / s, low system cost, high speed and reliable. Fieldbus ProFibus instruction set streamlined, programming is very convenient. Metering pumps with fieldbus ProFibus communication function, with all manual adjustment functions, can easily be incorporated into advanced, distributed computerized control systems to make their various functions more fully available and become modern precision metrology Pump leader. ProMax metering pump family that is, there are three series of dozens of models equipped with fieldbus capabilities. R & D of metering pumps has gone beyond its traditional pursuit of pure capacity and material quality, and turned to the direction of high precision, versatility and intelligence. This trend has become the consensus of major metering pump manufacturers in the world.