Abstract: Automatic bridge balancing apparatus includes a reference impedance and a measuring terminal pair for receiving an unknown impedance. A source of a test signal is coupled to the reference impedance and the measuring terminal pair. A measuring detector is connected in series with the unknown impedance when connected to the measuring terminal pair to provide a measured signal. A reference detector is coupled to the reference impedance to provide a reference signal. A combiner combines the measured signal with the reference signal to provide an error signal. The reference detector includes an up/down counter coupled to a digital attenuator that provides the reference signal. A controller responds to the error signal to control the count in the up/down counter so that the associated digital attenuator provides a signal to the combiner that reduces the error signal so that the count in the up/down counter is characteristic of the unknown impedance.

Abstract: A heater control device for an air-fuel ratio sensor which comprises: an air-fuel ratio sensor comprising a sensor element which detects an air-fuel ratio state of exhaust gas of an engine, and a heater which heats the sensor elements; a heater current flow control means for controlling a value of a resistance of the heater to be a target resistance value; a harness having a couple of couplers at both ends thereof which connects between the air-fuel ratio sensor and the heater current flow control means; and a current detecting resistance which is incorporated in the coupler on the air-fuel ratio sensor side, or provided adjacent to said coupler on the air-fuel ratio sensor side, and which is connected to the heater in series and detects current of the heater.

Abstract: A portable resistance tester comprises a pair of regulator circuits used to drive a bridge circuit and a detector circuit when measuring the resistance values of "in-circuit" test nodes. The tester produces an audible signal when the resistance of a measured test node falls within, or without, a predetermined resistance range.

Abstract: A thermal conductivity cell in the form of a bridge is used as one of the resistors in a Wheatstone bridge network. The output of the thermal conductivity cell is applied to the input of a low noise amplifier, the output of which is differentiated by an R-C coupling network having a time constant selected to pass a substantial portion of the output signal from the thermal conductivity cell with minimum attentuation. The R-C differentiating coupling network effectively reduces DC errors due to drift and offset and shapes the output signal improving the signal-to-noise ratio enabling trace amounts of materials to be analyzed.

Abstract: A slip ring includes a rotor and a stator. Stator contacts are connected to a data acquisition unit. The rotor contacts are connected to an amplifier circuit mounted in a housing connected to and rotatable with a rotating member. A sensor mounted on the rotating member to which the rotor is also fixedly mounted generates an electrical output signal corresponding to a sensed operating parameter of the rotating member. The sensor output signal is amplified by the amplifier in the housing before being transmitted through the slip ring to the data acquisition unit. Vibration isolation is provided when required for the slip ring and the circuit board in the housing carrying the amplifier to dampen vibrations generated by the rotating member. Resilient pads are mounted on the circuit board and engage the housing attached to the rotor.

Abstract: A combustible gas sensor includes a housing defining an interior containing a reference bead and a measurement bead which are fully exposed by the removal of the shroud or can therefrom. The beads are electrically connected in series and the reference bead is connected in parallel with a resister to define one side of a Wheatstone bridge. A liner consisting of a disk defining an inner face and an outer face overlies the reference and measurement beads. The inner face of the disk is provided with a slot opening at the inner face which is dimensioned to receive the reference and measurement beads therein. The slot provides a confined space for fluid communication between the fully exposed beads. A through running opening is disposed in the disk on each side of the slot adjacent the end of the slot in which the reference bead is disposed. A channel extends from each of the openings and communicates with the slot.

Abstract: A circuit for measuring the R.M.S. voltage of a high frequency signal (e.g. 100MHz) comprises two series-connected ntc thermistors (TH1, TH2) in a bridge circuit which is energized by a current source (1). The unknown signal is applied across one (TH1) of the thermistors and the resulting change in the resistance causes a D.C. output voltage to appear across the balanced terminals (T3, T4) of the bridge. This output voltage is proportional to the square of the R.M.S. voltage of the A.C. signal. In another embodiment, two ptc thermistors are connected in parallel in a bridge circuit which is energized by a voltage source, and are used to measure R.M.S. current. In each case, the thermistors are preferably operated in a negative slope resistance portion of their voltage-current characteristic.

Abstract: A precision bridge measurement circuit connected to a current source providing a linear output voltage versus resistance change of a variable resistance (resistance temperature transducer) including a voltage follower in one branch of the bridge so that the zero setting of the transducer resistance does not depend upon the current source or upon an excitation voltage. The zero setting depends only on the precision and stability of the three resistances. By connecting the output of an instrumentation amplifier to a feedback resistor and then to the output of the voltage follower, minor nonlinearities in the resistance-vs-temperature output of a resistance-temperature transducer, such as a platinum temperature sensor, may be corrected. Sensors which have nonlinearity opposite in polarity to platinum, such as nickel-iron sensors, may be linearized by inserting an inverting amplifier into the feedback loop.

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.

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.