Pump Controllers Information
Pump controllers monitor flow and/or level variables, and control a pump accordingly to maintain the desired levels. Pump control can include simply turning a pump on and off, or more advanced controls for pump speed, output pressure, etc. Many pump controllers include rate indication features and totalizer, data logger, and chart recorder capabilities. Products that provide level or pressure control are also available. Level controllers monitor, regulate, and control liquid or solid levels in a process. Pressure controllers accept inputs from pressure sensors, transmitters, gauges, and other devices. These pump controllers then adjust and control the pressure to maintain or achieve a desired level. Some pump controllers are printed circuit boards (PCB) that can be plugged directly into a computer backplane. Others attach to a panel or bolt onto a chassis, wall, cabinet, or enclosure; mount in racks and include hardware such as rail guides, flanges, or tabs; or mount on a standard DIN rail. Benchtop or floor-standing pump controllers with a full casing or cabinet and an integral interface are also available.
Specifications for pump controllers include number of inputs, number of outputs, input types, output types, and number of zones (if applicable). The number of inputs equals the total number of signals sent to the controller. The number of outputs equals the total number of outputs used to control, compensate or correct the process. Input types include: direct current (DC) voltages, current loops, analog signals from resistors or potentiometers, frequency inputs, and switch or relay inputs. Output types include analog voltages, current loops, switch or relay outputs, and pulses or frequencies. Pump controllers can also send inputs or receive outputs in serial, parallel, Ethernet or other digital formats which indicate a process variable. Some pump controllers send or receive accept commands and inputs from information converted to an industrial fieldbus protocol such as CANbus, PROFIBUS®, or SERCOS, or other industrial automation protocol. PROFIBUS is a registered trademark of PROFIBUS International.
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Pump controllers use different control techniques. Limit control establishes set points or limits that, when reached cause the pump controller to send a signal to stop or start a process variable. Linear control matches a variable input signal with a correspondingly variable control signal. Signal conditioning, filtering, and amplification can be used to produce the proper output control signal. Proportional, integral, and derivative (PID) control requires real-time system feedback. Feedforward control provides direct-control compensation from the reference signal and can be open-loop or used in conjunction with more advanced PID control. Fuzzy logic is a type of pump control in which variables can have imprecise values (as in partial truth) rather than a binary status (completely true or completely false). Pump controllers can also use advanced or nonlinear controls with algorithms such as neural networking and adaptive gain.
Pump controllers differ in terms of media, user interface, and compliance. Liquid, solids or powders, gases or air, and steam are media choices. In terms of the user interface, pump controllers may include a digital front panel or have analog components such as knobs, switches, and meters. Computer-programmable, web-enabled, and Ethernet or network-ready devices are also available. In terms of compliance, pump controllers that are destined for sale in the European marketplace should meet the requirements of the Restriction of Hazardous Substances (RoHS) and Waste Electrical and Electronics Equipment (WEEE) directives from the European Union (EU).