Texas Instruments Corporation

Raytheon Company

Sensata Technologies, Inc.

David L Corkum

Thomas Richard Maher

Keith W Kawate

June Park

Michael K Holz

Eric A Wolf

Thomas R Maher

A circuit for protecting a voltage supply to a sensor from a transient event is provided. The circuit includes at least one buffer capacitor configured to provide output during the transient event, the output substantially equivalent to output of a regulated supply during normal operation of the sensor. A method of fabrication and a sensor are disclosed.

Circuit designs for induced transient immunity

Signal conditioning of multiple sense elements is shown for providing information to a system requiring high accuracy and robust fault coverage. A first signal conditioning ASIC () pre-conditions the sense element data and a second system control ASIC () mathematically solves predetermined compensation relations based on the output of ASIC () and stored compensation data to fully condition the sensor output signal(s). The sense elements () are each formed by two half bridges whose inputs are pre-conditioned by separate, identical signal conditioning paths to provide highly accurate sense and diagnostic information.

Variable condition responsive sense system and method

An ASIC ( ) conditions two independent outputs (VINM, VINP) of a full Wheatstone piezoresistive bridge ( ) in separate conditioning paths. Each path is provided with a bridge supply voltage (VHB , VHB ) which can serve as a temperature related input signal to respective offset and gain compensation control circuits. The half bridge outputs are inputted to respective amplifiers (U , U ) along with a selected percentage of the temperature dependent bridge supply voltage. The outputs of the amplifiers provide a signal proportional to respective half bridge output voltage. In one embodiment, the output of the amplifier (U ) in one conditioning path of one half bridge is connected to the input of an amplifier (U ) in the other conditioning path to provide a signal in the one path proportional to the Wheatstone bridge differential output voltage and in the other path a signal proportional to the Wheatstone half bridge output voltage. In another embodiment, the temperature dependent bridge supply voltage is multiplexed for a selected time upon power-up to an amplifier (U ) which normally receives an input from one of the bridge outputs.

Low cost asic architecture for safety critical applications monitoring an applied stimulus

A full Wheatstone bridge sensor has conditioning electronics of an ASIC connected thereto. Two independently controlled diagnostic switches (S1, S2) in the ASIC are commonly connected to one of the bridge output nodes. The first diagnostic switch connects first resistor between the bridge output node and bridge supply voltage and the second diagnostic switch connects a second resistor between the bridge output and bridge ground. The first diagnostic switch closes during a first diagnostic waveform phase and opens during all other phases of operation. The second diagnostic switch closes during a second and third waveform phase and opens during all other phases of operation. The diagnostic waveforms are used to test major signal conditioning and fault reporting paths of the ASIC.

Method and apparatus for fault detection in a resistive bridge sensor

Detection of excessive negative offset of a condition responsive sensor such as a pressure responsive full Wheatstone bridge element ( ) and circuitry associated therewith is obtained by taking the sensor's output signal, preferably after the signal has been compensated for both gain and offset and comparing (Q ) the signal (V ) with a reference voltage (V ) selected to reflect an unobtainable stimulus input condition and driving the compensated signal to a fault level when the compensated signal exceeds the reference voltage.

Method and apparatus for providing detection of excessive negative offset of a sensor

An electronically variable light attenuator and method for electronically attenuating light. The attenuator has an array of liquid crystal regions. The regions in a first set thereof are interspersed with the regions in a second set thereof. The array is adapted to receive a beam of light directed along an axis. A pair of electrodes is provided. At least one of the sets of regions is disposed between the electrodes. The regions in the first set are configured to produce a first diffraction pattern in response to the received light and the regions in the second set are configured to produce a second diffraction pattern in response to the received light. The pair of electrodes are arranged to enable the first and second diffraction patterns to combine with a degree of interference along an axis selected in accordance with an electric field produced between the pair of electrodes and through the at least one of the sets of regions. The array degree of interference is greatest in the absence of the electric field. With such an arrangement, a relatively low cost, high power, fail-safe, electronically variable light attenuator is provided.

Electronically variable light attenuator

An in-range fault detection system for a full wheatstone bridge element ( ) having piezoresistive elements (R , R , R , R ) has bridge outputs (INP, INM) connected to measuring means in the form of a first circuit portion ( ) to provide a common mode voltage (V ). A second circuit portion ( ) is used to provide a centering voltage (C*V ) equal to the common mode voltage at the time of sensor calibration and a third circuit portion ( ) is used to provide a small window voltage (W*V ) which is a fraction of bridge voltage. The value (W*V ) is subtracted from (C*V ) at a first summing circuit (SUM ) and added to (C*V ) at a second summing circuit (SUM ) and the results are each compared to the common mode voltage by comparators (Q , Q ) which are then determined to be within or without a window of valid values by an OR gate (Q ).

Method and apparatus for in-range fault detection of condition responsive sensor

A potentiometric digital to analog converter includes switches to electrically connect a string of n resistors between two voltage supplies to charge a first capacitor (C,) through a first tap and store the charge and then to reverse the electrical connections of the string to the two power supplies to charge a second capacitor (C,) through a second tap connected at an inverse location symmetrical about the average voltage of the voltages at the supply connectivity switches and store the charge of the second capacitor. The voltage (V,, V,) on the two capacitors is then averaged to provide a ratiometric output voltage which is insensitive to the drift of values of the string of resistors.

Potentiometric DAC having improved ratiometric output voltage stability

A first embodiment of a condition responsive capacitive transducer, such as an accelerometer (1), is shown in which an electrically conductive sensor element (14) is sandwiched between upper (10) and lower (12) electrically insulative planar substrates and mounted in sealed, spaced apart relation by patterns (16) of adhesive containing spacing elements. A second embodiment (100) includes a signal conditioning capacitor having plate portions (114r, 120b and 114s, 120c) on either side of a condition responsive capacitor to minimize errors caused by translational movement of the sensor element (114) relative to the substrates (110, 112). Circuit conditioning electronics (124) is shown mounted directly on one of the substrates (110) and the sensor is mountable directly on a circuit board. A third embodiment (200) shows differential capacitors (224, 226, 228, 230, 232, 234) for minimizing errors due to misalignment of the movable element (114) with respect to the fixed supports (210, 212). Another embodiment provides a material system for use in condition responsive capacitive transducers having refractory metal for a sensing element and glass material for a supporting substrate.

Condition responsive sensor having a signal conditioning capacitor

A condition responsive capacitive transducer, such as an accelerometer, is shown using a material system having refractory metal for the sensing element and glass material for a supporting substrate. The refractory metal is preferably tungsten, tantalum or molybdenum, and is coated with a glass seal enhancing material, such as titanium or nickel.

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Attleboro, MA, United States of America

David L Corkum