Abstract: A method of digital temperature compensation uses a digital temperature compensation word to produce a digital word modification of a digital input to a temperature sensitive digital to analog converter hereinafter converter. The method includes the steps of sensing the temperature affecting the converter to produce a digital temperature representation which is used by a digital computer to produce an output in accordance with a characterization equation in the form of Output=f(D, M) where D=digital data and M=f(temperature). The temperature stability of the converter is affected by the temperature stability of a reference voltage circuit used in the converter and having a voltage reference diode. A compensation circuit uses a temperature sensor in the form of a second diode, which is thermally coupled to the reference diode, and a tracking type analog-to-digital converter for converting an analog signal.

Abstract: A sensor communication system uses a shared analog signal to duty cycle converter for producing a comparison between a predetermined free-running triangular waveshape and a selected output signal from a plurality of analog signal sources such as process sensors, to convert the amplitude of the analog signal to a variable duty cycle signal. The variable duty cycle signal is subsequently converted to a digital signal which may be represented by a count stored in a counter counting clock pulses during the occurrence of the pulse width waveshape of the variable duty cycle signal. The digital signal is utilized as a digital word by a microprocessor operating in accordance with a stored program to produce a characterized digital output signal for use in a communication after conversion to a 4-20 ma control signal for communication and control in an industrial process control system.

Abstract: A power supply structure for an electronic system includes a primary power source and a stand-by or secondary power source. The secondary power source is ground circuit isolated from the primary source. A monitoring circuit, which is energized from the secondary source is connected to monitor the primary source for incipient failure, then to produce an output signal which may be used to trigger an alarm and/or switch the secondary power source into energizing connection with respect to the electronic system.

Abstract: A multi-input signal comparator and indicator circuit for comparing a plurality of signal levels with a reference level and an indicator circuit arranged to respond to a comparator output signal for indicating an error in any of the comparator input signals. A high and a low comparator is used for each input signal to provide a "window" comparison while separate indicators provide a readout of high and low errors.