Abstract: A field device electronics for a conductive, limit-level switch, with a conductive probe and a measuring circuit including a control/evaluation circuit. The measuring circuit, a measuring bridge circuit is present, with at least one coupling capacitor (C2) being present for the DC voltage separation of the probe from the measuring circuit, and with the at least one coupling capacitor (C2) being integrated into the measuring bridge circuit.

Abstract: A battery cell balancing method and apparatus. A simple and inexpensive method and apparatus to balance the cells within a battery configuration where at least some of the cells are arranged in series or a combination of series and parallel. One embodiment balances the cells proportionally to the level of imbalance between the cells. This embodiment is adaptable to more than two cells in series. Another embodiment balances the cells with a constant current. This embodiment will more quickly balance the cells because of the constant current. Components are selected in specific positions to reduce the current draw of the circuit and the effect on the system. The invention injects current into or withdraws current from a position between series cells to be balanced based on whether the voltage is higher or lower than the fractional voltage needed for the cells to be in balance.

Abstract: A digital synchro/resolver bridge is provided, which may be operated individually, or optionally, may be interfaced with a computer for inclusion in an automated test system. The digital bridge includes a plurality of relay modules operated by an embedded processor to digitally set taps for a plurality of integral transformer windings. The bridge provides feedback to the computer in the form of status messages and also to the front panel thereof, for local mode (i.e., stand along) use. The resolver bridge utilizes a standard communication interface, such as a conventional RS232 interface. The resolver bridge performs a power-on self-test to insure accurate calibration prior to testing of individual resolvers.

Abstract: The present compensating circuit operates to reduce the span shift error due to ambient temperature changes of a span resistance compensated, bridge array circuit arrangement for a semiconductor transducer employing piezoresistive sensors. The span resistance method alone cannot reduce the span shift error to less than one percent (1%) for full scale. The present compensating circuit applies a constant voltage source, derived from the voltage source applied to the transducer, to a non-inverting input to an operational amplifier. The circuit also applies an ambient temperature dependent voltage, derived from the ambient temperature dependent bridge resistance of the bridge array circuit, to an inverting input of the operational amplifier. Both inputs to the operational amplifier are fed back through a different resistance loop to control the output voltage in response to the non-linearity of the ambient temperature dependent bridge resistance.

Abstract: A feedback operated DC bridge circuit for monitoring the voltage variations in a voltage divider circuit using a voltage controlled resistance component to reach a null balance across the bridge. Amplification is provided at higher accuracy near the null point when the voltage difference across the bridge is zero. The feedback bridge circuit includes an integrator which directly drives the controlling component to the value of the resistance in an unknown branch to force the null condition. The voltage controlled component (configured as a discrete metal oxide semiconductor device or bipolar junction transistor) and the balancing scheme are suitable for microfabrication and provides noise-rejection enhancement. The interconnected integral feedback of the autonulling DC bridge enables both a neural network for pre-processing sensor input in a spatial domain as well as general analog computation that mimics a first order differential equation in the form of the system state equation.

Abstract: A fuse blown detection circuit for use in conjunction with the control transistor output circuits of a programmable controller which provides low leakage after the fuse is blown. The detection circuit comprises a pair of voltage dividers and a diagnostic triggering device forming an H-bridge network connected across the terminals of the fuse and a blocking diode. When the fuse is blown the voltage levels defined by the dividers change to activate the trigger device and enable a diagnostic signal indicative of the fuse blown condition while the blocking diode prevents current flow back through the control transistor and output circuit.

Abstract: A circuit disclosed maintains ratiometric analog inputs to an integrated circuit using a network of resistors, some of which are external to the integrated circuit and some of which are internal to the integrated circuit, reducing expense. The analog inputs maintain a fixed ratio during fluctuations in supply voltage and fluctuations in temperature.

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: In order to compensate for the effects of temperature variations on a transducer such as a piezo-resistive bridge, the bridge is fed from a temperature dependent power supply circuit. The power supply circuit comprises a temperature sensitive element with first and second adjustment means for adjusting the slope of supply voltage for the transducer against temperature on first and second sides, respectively, of a predetermined temperature. The second adjustment means provides an adjustment which is independent of the first adjustment means so that repeated temperature cycling during calibration is unnecessary.

Abstract: There is disclosed a phase-controlled switching circuit, comprising a controlled rectifier (e.g. bidirectional triode thyristor); an amplifier connected at its output terminal to the gate of the controlled rectifier; an ac Wheatstone bridge having at one of its arms a variable resistance (e.g. thermistor to CdS photoconductive cell), said ac Wheatstone bridge being connected at one branch to the input terminal of the amplifier and at its other branch between the cathode and anode of the controlled rectifier through a load; a time constant circuit connected with the variable resistance; a pair of mechanical contacts (e.g. relay) connected in parallel with the controlled rectifier and a dc source for electrifying the whole circuit.

Abstract: A sensing circuit system including circuitry for sensing impedance variations of a variable impedance element. As disclosed, a bridge circuit system includes a bridge circuit to which the variable impedance element is couplable. The bridge circuit system further includes circuitry for detecting open circuit or short circuit fault conditions of the variable impedance element. The variable impedance element is coupled to the bridge circuit by a connector, having two connector components, which is also operable to couple the fault detection circuitry to the bridge circuit only when the two components of the connector are connected together.

Abstract: A heater control circuit functions in conjunction with a suitable heating coil to provide precision, automatic temperature regulation. The combination of heating and temperature sensing functions into a single system results in a two-wire heater regulator control circuit in which a continuous excitation voltage and a power voltage can be simultaneously present at the heater coil. Temperature of the heater is established by continuous excitation and sensing independent of the occurrence of power for heating. A short circuit protection circuit is responsive to an electrical short in the heater coil (which significantly changes its resistance with temperature) and disables the power voltage.

Abstract: Device for conversion of a nonelectrical quantity into an electrical signal comprises measuring and compensating bridge circuits whose supply arms are connected to a power supply. A nonelectrical quantity like strain, force or pressure acts on the input of the measuring bridge circuit whose output is coupled to the input of a measuring circuit. The effect of destabilizing factors, such as temperature, electromagnetic field or aging of device components, is reduced by a suitable compensating bridge circuit whose output is connected to the input of a correction circuit. The measuring bridge circuit is one arm of the compensating bridge circuit. The correction circuit has differential outputs coupled to adjustable dividers whose number is equal to the number of compensating couplings introduced. Outputs of the dividers are connected to a displacement unit and to a device functional characteristic scaling circuit.

Abstract: A self-balancing DC-substitution measuring system includes a temperature dependant resistor (TDR) which is placed in one leg of a Wheatstone Bridge circuit, diagonally opposed first and second nodes of the bridge being driven respectively by the outputs of two operational amplifiers such that the potential at each of these first and second nodes, when measured with respect to a common reference point is equal in magnitude and opposite in polarity to the other. Each of the amplifiers has a pair of differential inputs and each of these inputs are connected to either of the remaining third and fourth nodes of the bridge circuit or to the common reference point, no two inputs from the same amplifier being connected to the same point and each of the third and fourth nodes and the common reference point having at least one amplifier input connected to it.

Abstract: A temperature compensation circuit is provided which can be used for span temperature compensation in an electropneumatic transducer system and which includes a constant current generator circuit coupled to a bridge of piezo resistances in a pressure transducer to supply a constant current through one piezo resistance of the bridge to common. The Electropneumatic Transducer System includes a zeroing circuit, a voltage chopping circuit, a linearity correction circuit, a low-current shut-off circuit, and a high-current shut-off circuit to provide hard turn-ons and hard turn offs of the system at the lower and upper ends of the pressure output range or span. The Electropneumatic Transducer System also includes a voltage railsplitting circuit arrangement to minimize the operating currents, and voltages. With these features, the Electropneumatic Transducer System is particularly adapted for use in hazzardous combustible atmospheres where Intrinsic Saftey and accuracy are required.

Abstract: A resistance thermometer in which a temperature sensing resistor is connected in parallel with a series combination consisting of a signal output resistor and a compensating resistor. By choosing the resistance ratio between two resistors to be equal to the ratio of the desired resistance value to the error of the temperature sensing resistor, the output voltage developed on the signal output resistor reflects the voltage expected on the temperature sensing resistor without the resistance error thereof. The temperature sensing resistor and the compensating resistor constitute a circuit unit which is detachable from the rest of the resistance thermometer.

Abstract: A moisture sensing element is provided and is constructed of a body having therein a first zone formed of porous material with a first range of pore size having a first mean pore size and a second zone formed of a porous material with a second range of pore size having a second mean pore size such that in use the body is located within a desired soil area under surveillance whereby both the first and second zones are placed in hydraulic conduction with the desired soil area. The first mean pore size is substantially greater than the second mean pore size such that the second zone will remain hydrated when the first zone is becoming dehydrated. Electrode elements are associated with each of the first and second zones in spaced relation and define therebetween respective electric current flow paths through each of the first and second zones for sensing an electrical property of each of the zones.

Abstract: A switching device is provided, for measuring capacities, comprising n branches in parallel with n.gtoreq.1, each branch being formed by a capacity to be measured and a switch, the assembly of switches being subjected to a control signal which successively connects each capacity in parallel across the measuring bridge. Each switch may assume two positions, one of the positions connecting electrically the first plate of the capacitor to be measured to one of the ends of the measuring bridge, the other position connecting electrically the first plate to the second one and to the other end of said measuring bridge.

Abstract: The present invention is directed to a circuit for generating a voltage for compensating the output of a thermocouple. The circuit provides a compensating voltage to enable the thermocouple to be operated with its reference junction at ambient temperature. The compensation voltage varies linearly with changes in the ambient temperature and passes through zero volts at 0-20 C. The compensation voltage is generated by combining a temperature variable voltage developed across one or more semiconductor junctions with a constant voltage of opposite polarity.

Abstract: A security system of the bridge circuit type has in one of its arms a conducting element whose impedance is to be monitored and in its other arms reference and/or compensating elements, for detecting an unbalance of the bridge resulting from a sudden change in the impedance of the conducting element. At least one of the reference elements has a variable impedance. The phase shift of the signal obtained at the output of the bridge circuit is detected, due to the drift of the bridge circuit, with respect to the A.C. supply frequency. The detection signal is then used for compensating the drift by acting on the reference element having a variable impedance in order to bring the bridge circuit back to balanced condition.

Abstract: A diode equalizing bridge wherein one pair of opposed diodes are forward-biased and a second pair of opposed diodes are reverse-biased so that the two capacitors at the opposed load terminals are charged and discharged by a current source and current sink connected to two opposed power terminals until the capacitors have equal voltages. The current source and sink are gated to activate and deactivate the bridge. For an AC power source, two diode bridges are used, one connected to each terminal of the capacitor to operate during the respective half cycle of the AC power source.

Abstract: An apparatus for driving a hot-wire air-flow sensor of constant temperature difference type includes a hot wire and a temperature sensitive compensating element such as a resistor for compensating temperature of air. The hot wire and the resistor are formed of identical elements. A pulse train signal having a pulse width varying in correspondence to difference between voltage drops produced, respectively, across the hot wire and the compensating resistor supplied with a constant current is produced for interrupting the current supplied to the hot wire.

Abstract: A temperature compensation circuit is provided which can be used for span temperature compensation in an electropneumatic transducer system and which includes a constant current generator circuit coupled to a bridge of piezo resistances in a pressure transducer to supply a constant current through one piezo resistance of the bridge to common. The Electropneumatic Transducer System includes a zeroing circuit, a voltage chopping circuit, a linearity correction circuit, a low-current shut-off circuit, and a high-current shut-off circuit to provide hard turn-ons and hard turn offs of the system at the lower and upper ends of the pressure output range or span. The Electropneumatic Transducer System also includes a voltage railsplitting circuit arrangement to minimize the operating currents and voltages. With these features, the Electropneumatic Transducer System is particularly adapted for use in hazzardous combustible atmospheres where Intrinsic Saftey and accuracy are required.