Phillips Petroleum Company

Applied Automation, Inc.

James E Layton

Earl E Shriver

A recirculating type analog to digital converter is disclosed which has an auto-zero mode that is introduced prior to each conversion cycle. The loop is based on an arrangement of operational amplifiers and FET switches, and further includes a comparator circuit, a reference voltage source and a microprocessor which are coupled to the loop. Also coupled to appropriate points in the loop are three time gated integrator circuits which generate analog signals which respectively compensate for offset voltages of operational amplifiers in the loop, the offset voltage of the comparator circuit which is coupled to this loop, and the gain of the loop. The compensating signals which are generated in the auto-zero mode are applied to the loop during the conversion cycle.

Recirculating analog to digital converter with auto-calibrating feature

A waveform generator is provided which is capable of generating simultaneously a plurality of electrical signals which have different waveforms. The waveform generator is completely battery operated and is particularly useful in testing multichannel devices where power is not available for standard waveform generators. A voltage regulation circuit is provided which provides a regulated voltage from a battery pack for use by the waveform generator. The forward voltage-current characteristics of the base emitter junction of a silicon transistor are used as the basis for the generation of a reference voltage for the voltage regulation circuit to thereby substantially minimize the battery drain caused by the use of a voltage regulation circuit.

Waveform generator

A waveform generator is provided which is capable of generating simultaneously a plurality of electrical signals which have different waveforms. The waveform generator is completely battery operated and is particularly useful in testing multichannel devices where power is not available for standard waveform generators. A voltage regulation circuit is provided which provides a regulated voltage from a battery pack for use by the waveform generator. The forward voltage-current characteristics of the base emitter junction of a silicon transistor are used as the basis for the generation of a reference voltage for the voltage regulation circuit to thereby susbtantially minimize the battery drain caused by the use of a voltage regulation circuit.

A gain ranging amplifier system is provided for use in the acquisition of data. Voltage offset compensation is utilized to correct errors in the gain ranging amplifier system caused by thermal drift and temperature dependent voltage offsets, both of which are associated with amplifiers in the gain ranging amplifier system.

Gain ranging amplifier

An analog signal representative of the condition of a process variable and an analog set point signal representative of the desired value of the process variable are compared to provide an analog error signal. In response to the analog error signal the controller generates a sign signal and a pulse rate signal which can be utilized to increase or decrease the digital value stored in a counter from which a process control signal is generated. In a preferred embodiment the process controller of the invention is utilized as a backup controller for a direct digital control system and utilizes the same digital output, digital to analog conversion, and analog output components as the associated direct digital controller.

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Bartlesville, OK, United States of America

James E Layton