Abstract: Computations are performed on the digital representation of an analog signal in a digital processor. The output of the processor is applied through a digital/analog converter to a sample and hold circuit. The analog signal is applied to the processor through a comparator which receives at a second input the output of the digital/analog converter. In a mode other than the computation mode the processor controls an analog/digital conversion by means of a loop including the processor, the digital/analog converter, and the comparator.

Abstract: An electric controller system includes a comparator at the input of a processor, the processor including a program memory, an operation control unit and a data memory. A digital/analog converter is provided at the processor output. Analog/digital conversion is by means of a loop including the processor, digital/analog converter and comparator. The digital/analog output is also received by an analog signal hold means, the output of which is fed back to the comparator. A manual control circuit operable only in a manual control mode provides an alternative input to the analog signal hold means. Computations in the processor are thus based on a manual input through the hold circuit and comparator only during the manual control mode. Bumpless switching from the manual mode to an automatic mode is provided while further providing for a manual output with failure of the processor. Further embodiments include a multiplexer at the input, a plurality of hold circuits and parameter setting circuits at the input.

Abstract: A process control system of the type arranged to accept varied forms of analog sensing signals from field sensing devices, to digitally process data represented thereby, and to supply varied forms of analog control signals to field control devices. The system is characterized by signal converter means which convert data between the varied analog forms generated by the field devices and a standard form of intermediate signal, e.g., a pulse-width signal, which carries data as a function of duration. The intermediate signals facilitate signal transmission, editing, and isolation, and permit the process control system to have a simple, noise-free, easily adaptable structure. Digital interface means then convert data between the intermediate signals and digital signals in a form suitable for use by digital data processing means.

Abstract: A signal transmission system of the type used in process control systems for conveying a signal between a field telemetering instrument and a central controller, or between a central controller and a process control device. The signal transmission system is arranged with a transmitter accepting an input signal, a transmission line for carrying a transmission signal, and a receiver receiving the transmission signal and developing an output signal.In accordance with the invention, converter means in the transmitter develop a pulse width signal with a duration corresponding in a predetermined manner to the value of the input signal, and means in the transmitter provide the transmission signal (e.g., a current signal) with two states (e.g., opposite polarities), one of which has a duration corresponding to the duration of the pulse width signal.