Abstract: The output of a condition sensing bridge is linearized by providing a feedback from the output to the bridge supply which feedback is in the linear form of V.sub.B =KV.sub.O +V.sub.X where V.sub.B is the bridge supply voltage, K is a proportionality constant, V.sub.O is the bridge output and V.sub.X is the feedback offset voltage.
Abstract: A system and method for calibrating a transducer having a bridge-type network. The calibration includes a source of constant current and a calibration circuit including the source connected across one of the resistive-type transducer elements of the bridge. Switching means are provided in the calibration circuit so that the current can be selectively supplied to or withheld from the resistive-type transducer element across which the calibration circuit means is connected for producing a calibration signal. The calibration signal is substantially independent of the transducer output regardless of whether or not the signal is temperature compensated and whether it is switched mechanically, electromechanically, or electrically. An internal calibration resistor in the current source is used to make the current inversally proportional to the bridge arm resistance. The calibration resistor tracks the resistive-type transducer elements of the bridge over temprature.
Abstract: A voltage-to-digital converter comprising a storage circuit for providing a storage capacitance with a plurality of selectable magnitudes. The storage circuit provides a charge output representative of applied voltage input signals and the selected capacitive magnitude. A charge accumulation circuit is coupled to the charge output. The total charge accumulated is proportional to the integral of the amount of charge discharged from the storage circuit. The charge accumulation circuit provides a balance output representative of a comparison of the accumulated charge and a reference charge.
Abstract: A circuit for detecting resistance changes in an electrically resistive device is disclosed. The circuit comprises a bridge circuit with first and second MOSFET transistors in adjacent arms of the bridge and the resistive device and a comparison resistor in the other adjacent arms of the bridge. The first MOSFET transistor is connected in series with the resistive device across input terminals of the bridge and the second MOSFET transistor is connected in series with the comparison resistor across the input terminals of the bridge. The drains of the transistors are connected together and the gates of the transistors are connected together. The resistance of the second transistor is higher than the resistance of the first transistor by a predetermined multiple and the resistance or the comparison resistor is greater than the nominal resistance of the resistive device by the same multiple.
Abstract: An apparatus for measuring differential impedances which incorporates a CMOS timer in place of the sine wave generator in a typical AC bridge configuration. A toroidal signal transformer having its primary and secondary windings tightly twisted together and wound around the core lessens temperature drift characteristics. The differential bipolar current signal provided by the secondary winding is passed through an AC to DC converter which is switched by a field effect transistor, thereby eliminating the need for prior art inverter comparator circuits. Finally, by use of a bandpass filter after the signal transformer and by insertion of a capacitor before the AC to DC converter, the need for the active filter stage used in the prior art is eliminated.
Abstract: In the case of a circuit arrangement with a flow probe operated in a bridge circuit, a device for determining bridge balance, which controls a triggering circuit which can be supplied by an oscillator and controls a switching device for the power supply of the bridge circuit, the oscillator has an operating frequency which is at least approximately inversely proportional to the square of the operating voltage of the power supply.
Abstract: A catalytic combustion type CO gas sensor which is composed of an electrical circuit by serially arranging two coils composing an active section and a compensating section, and by providing serial bridge resistances, r.sub.1 and r.sub.2, opposing to the said coils, respectively, and via a gas sensitometer, and which determines the CO concentration based on the difference in value of resistance of both coils of the active section and the compensating section on catalytic combustion of CO, characterized by:(A) that the values of the resistance of coils of the active section and the compensating section and bridge resistances, r.sub.1 and r.sub.2, at a definite temperature are made substantially the same, and thus the temperature coefficients of the coil of the active section and the bridge resistance r.sub.1, and of the coil of the compensating section and the bridge resistance r.sub.2 are made approximately the same.(B) that the value of resistance of the coil of the active section at 150.degree.-200.degree.
Abstract: A temperature limited catalytic gas detector includes a catalytic gas sensor in one branch of a Wheatstone bridge network. A power supply is connected through a voltage controlled regulator to the bridge network. An instrumentation amplifier measures electrical imbalances across the bridge network. A display is connected to the output of the instrumentation amplifier. The detector also includes a comparator which compares the output of the instrumentation amplifier with a predetermined limit signal and produces an output when the output of the instrumentation amplifier exceeds the limit voyage. The regulator is responsive to the output of the comparator to thereby reduce the power supply to the bridge network. The limit signal is equivalent to the output of the instrumentation amplifier when the gas sensor is at a particular high temperature. The arrangement prevents the gas sensor from operating at excessive operation temperatures.
March 6, 1989
Date of Patent:
October 8, 1991
Perry A. Palumbo, Oscar Singleton, Louis G. Gaetano
Abstract: A procedure and a device for determining corrosion of preferably insulated structural parts (2) assures in a simple way early detection of corrosion. For this purpose an electric conducting resistance wire (4) exposed to the same corrosive medium, e.g. condensation water, as the structural part (2) to be examined for corrosion is placed outside the structural part (2) and the electrical resistance of the resistance wire is measured. The effective cross-section of the resistance wire (4) and its electrical resistance change with the corrosion of the resistance wire (4) so that the resistance change of the resistance wire (4) registers the effect of the corrosive medium.
Abstract: A bridge balancing circuit includes a bridge having a resistance change type sensor, a differential amplifier for extracting a voltage difference across two central nodes of the bridge, a comparator connected to the output terminal of the differential amplifier, a D/A converter an output terminal of which is connected to one of the two central nodes, and a controller for controlling the D/A converter. The differential amplifier and the comparator automatically detect a balanced point of the bridge, and the controller maintains a balanced state of the bridge.