![]() ![]() Digital SignalĪ discrete value at which an action is performed. DeviationĪny departure from a desired or expected process value. DelayĪ term commonly used in stead of dead time. With derivative action the controller output is proportional to the rate of change of the process variable or process error. The derivative - D - part of a PID controller. Dead Timeĭead time is the amount of time it takes for the process variable to start changing after changing output as a control valve, variable frequency drive etc. The range through which an input can be varied without initiating a response. Replaced by OLE for process control - OPC. DDE Windows Dynamic Data ExchangeĪ standard Microsoft operating system method for communicating between applications. ![]() The output of the master controller is the set point for the "slave" controller. Two or more controllers working together. In auto mode the output is calculated by the controller using the error signal - the difference between set point and the process variable. Analog to Digital Converting, A-D ConvertingĮlectronic hardware converts analog signal like voltage, electric current, temperature, or pressure into digital data a computer can process and interpret. Usually the electrical current signal is of magnitude 4-20 mA where 4 mA is the minimum point of span and 20 mA is the maximum point of span. Analog signals are like voltage or electric current signal, representing temperature, pressure, level etc. ![]()
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