Two term process controller with digital integration - integrator utilises voltage to frequency converter coupled to bidirectional counter

摘要

A two term process controller is based upon an analogue channel and a digital integrating channel. An input voltage is fed to an analogue-to-digital converter in the form of a voltage to frequency signal converter. The output frequency is processed in a frequency dividing circuit with a number of pick-off output lines. The output of the frequency divider is used to change the state of a bi-directional counter coupled to a digital to analogue converter. Directional control of the bidirectional counter is exercised directly from the voltage to frequency converter. In the fully automatic mode of the output of the digital to analogue converter is compared with the input voltage and the difference stored in an analogue memory. For smooth change-over to the manual mode a standard frequency signal is substituted upon direction of a control circuit.