Leeds & Northrup Company

Drexelbrook Controls, Inc.

Howard S Hoopes

Frederick L Maltby

Thomas J Walsh

Steven R Petersen

Jonathan L Kramer

Richard G Hall

James W Zecca

Robert W McClenahan

Samuel A Arcara

A two-wire, admittance-responsive instrument system in which a transmitter, receiver and calibrator are connected by a two-wire transmission line is disclosed. The calibrator repetitively transmits a calibration enabling signal causing the transmitter to increment a reference admittance for comparison to a sensed admittance corresponding to a known physical condition. The calibrator monitors the bistable output signals transmitted by the transmitter in the calibration mode, which changes state when the incremented reference admittance bears a predetermined relationship to the sensed admittance. The calibrator may then transmit additional calibration enabling signals causing preload to be established for transmitter operation.

Remotely calibratable instrument system

A circuit for preventing data transfers to a RAM by a microprocessor when primary ac power fails also puts the RAM in standby after a period adequate to complete any data transfer started. The sequence is provided by providing a first signal to the microprocessor transfer enable line upon loss of primary power. A second signal is provided for the enable line of the RAM after a predetermined delay but before decay of the dc power to the RAM.

Power failure early warning circuit for microprocessor with CMOS RAM

A string of short pulses is impressed across the input circuit of a multipoint recorder and a pulse magnitude detecting circuit. If the input circuit is open, the magnitude of the pulses appearing at the pulse magnitude detecting circuit is higher than would be the case if the input circuit were completed by a normal input device. The pulse magnitude detecting circuit is operable to apply to the measuring circuit of the multipoint recorder a positive potential whenever the pulse detecting circuit detects pulses of a magnitude indicating that the input circuit is open. As a result, the multipoint recorder is driven upscale to its limit where the particular point which is open-circuited is identified by a printed indicia.

Open circuit detector for multipoint recorder

A servo system is disclosed which produces a mechanical position varying in accordance with variations in an electrical input signal. The input signal is applied by an amplifying channel to one input of an error amplifier. The input signal amplifying channel includes an integrating amplifier and a voltage limiting device at the input to the integrating amplifier so that the signal applied to the error amplifier has a limited rate of change. A negative feedback gain determining loop is included in the amplifying channel so that at balance the signal applied to the error amplifier is directly related to the input signal. Applied to the other input of the error amplifier is a signal representative of the positional output from the servo system to form a second rebalanceable loop system. A switched stop circuit is connected from the output of the error amplifier to the input of the integrating amplifier to permit the servo system to be stopped and subsequently to restore the system to normal operation with the rate of change of position of the servo limited by the integrating amplifier.

Servo stop system

A digital signal linearizer for obtaining a linear digital output from a non-linear input. The output voltage of a thermocouple is converted to a train of pulses by a dual slope analog to digital converter. The number of pulses in the pulse train is proportional to the voltage and is linearized by a pulse rate multiplier programmed to vary over successive ranges of pulse counts corresponding to linear segments approximating the non-linear characteristic relating temperature and voltage. The linearized pulse train out of the multiplier is counted and displayed directly in temperature units.

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Hatfield, PA, United States of America

Howard S Hoopes