Abstract: A resistance testing apparatus makes use of a modular design for cascaded, parallel, bipolar current sources to obviate the need for electromechanical or pneumatic switching systems.

Abstract: A control circuit includes a clock pulse generator operable to output a pulse-frequency ratio to a constant voltage source in order to control the power output of the constant voltage source. The control circuit further includes a driver circuit for the clocked control of at least one light emitting diode (LED) to which a measurement resistor is connected in parallel. The LED is supplied with power by the constant voltage source. The LED is turned on when the power is greater than a forward power level and is turned off when the power is less than the forward power level. The driver circuit taps a measurement voltage of the measurement resistor while the LED is supplied with power less than the forward power level. The clock pulse generator varies the pulse-frequency ratio as a function of the measurement voltage of the measurement resistor.

Abstract: A method for the temperature compensation of a resistance measuring bridge, such as in particular a Wheatstone bridge, is characterized in that a capacitor positioned between the input circuit and a resistance switching circuit of the Wheatstone bridge is successively discharge by means of at least one Wheatstone bridge resistor. In a device for the temperature compensation of a measuring bridge, particularly a Wheatstone bridge, having a measuring bridge and a compensating resistor in the input circuit, one or two switches are located in the resistance switching circuit branch of the measuring bridge as a contact point with the latter and a capacitor is located between the input circuit and the resistance switching circuit branch.

Abstract: A method for operating a sensor element having two contact terminal pairs, comprises steps of providing a first measurement value by applying a first controlled variable having a first polarity between the first terminal pair, and coupling the second terminal pair with output terminals; providing a second measurement value by applying a second controlled variable, having an opposed polarity, between the first terminal pair, and coupling the second terminal pair to the output terminals; providing a third measurement value by applying the first variable between the second terminal pair, and coupling the first terminal pair with the output terminals, providing a fourth measurement value by applying the second variable between the second terminal pair, and coupling the first terminal pair with the output terminals; and determining a sensor signal on the basis of a difference between the first and second values and a difference between the third and fourth values.

Abstract: A bridge sensor emulator includes a first emulation circuit programmable to emulate an output signal of the bridge circuit under 11 conditions each including a different combination of applied stimulus and temperature. A second emulation circuit is programmable to emulate the temperature-sensing device for 3 temperatures. An excitation signal is applied to the first emulation circuit. One rotary switch is coupled to the first emulation circuit to select from it and emulate a bridge output signal. An emulated common mode sensor output voltage is also generated. Another rotary switch is coupled to the second emulation circuit to select from it and emulate one of three temperature output signals. In another embodiment, a microcontroller, nonvolatile memory, and three digital to analog converters are utilized to emulate the bridge sensor for the 11 conditions.

Abstract: A circuit for measuring the mass air flow rate through a duct is disclosed. The circuit includes a bridge circuit, a first amplifier, an oscillator, a comparator and a switch. The bridge circuit has a plurality of resistors arranged to output first and second bridge voltage signals. The first amplifier circuit receives the first and second bridge voltage signals and generates a differential bridge voltage signal. The oscillator provides an oscillating control signal. The comparator is in communication with the first amplifier circuit and the oscillator for comparing the differential bridge voltage signal to the oscillating signal to generate a pulse width modulated differential bridge voltage signal. The switch is in communication with the bridge circuit and the comparator. The switch selectively provides a power voltage signal to the bridge circuit at a frequency corresponding to the pulse width modulated differential bridge voltage signal.

Abstract: A physical quantity sensing device includes a bridge circuit that has first and second input points, to which an AC voltage is applied, and first and second output points connected to a differential amplifier. The bridge circuit includes a first bridge arm for electrically connecting the first input point to the first output point, a second bridge arm for electrically connecting the first output point to the second input point, a third bridge arm for electrically connecting the first input point to the second output point and a fourth bridge arm for electrically connecting the second output point to the second input point. The first bridge arm includes a first sensor element, of which the impedance changes with a physical quantity to be measured, and the second bridge arm includes a second sensor element, of which the impedance also changes with the physical quantity to be measured. The total impedance of the first and second bridge arms is smaller than that of the third and fourth bridge arms.

Abstract: An instrumentation current loop, including a transducer having transducer output terminals. A power source is connected in series to the transducer. A bridge has a first arm and a second arm extending between a pair of input terminals, where the input terminals of the bridge are connected to the transducer output terminals. The first arm comprises a first resistance and a second resistance connected via a first junction. The second arm comprises a third resistance and a fourth resistance providing a voltage reference connected via a second junction. A meter is connected between the first junction and the second junction. Values of the first, second, third and fourth resistance are selected so that a given range of input current provided by the transducer output terminals and supplied to the input terminals of the bridge is converted to a desired range of output current for the meter.

Abstract: A physical quantity sensing device includes an AC voltage generator for generating an AC voltage and a bridge circuit that has first and second input points, to which the AC voltage is applied, and first and second output points connected to a differential amplifier. The bridge circuit includes first and second sensor elements, the impedance of which change with a physical quantity to be measured. The first and second sensor elements have a positive temperature characteristic in which sensitivity increases as temperature rises. The AC voltage generator includes an amplitude limiter which has a negative temperature characteristic that decreases the amplitude of the AC voltage with a rise in temperature, thereby compensating for temperature dependence of a differential voltage produced between the first and second output points.

Abstract: In a method for detecting an offset drift in a resistive Wheatstone measuring bridge, a switch is made between a measuring mode and a testing mode without interfering in the internal structure of the measuring bridge. In testing mode, two sensor resistors that act in the same way and lie in different bridge arms in the measuring mode are connected in series, and a voltage level occurring in the connection of these sensor resistors is compared with a reference voltage. Preferably the sensor resistor that acts in a different way and lies between the two series-connected sensor resistors acting in the same way is bridged. The reference voltage is advantageously formed by resistive division of the voltage applied to the series connection of the sensor resistors. The testing mode may expediently be switched in such a way that the two pairs of sensor resistors acting in the same way are respectively tested in succession.

Abstract: An Audio Feedback Impedance Comparison Device to audibly express Impedance differences between/amongst components, circuits, materials, substances etc., to make use of the aural sense, while relieving eye, neck and mental strain, as well as reduce probe time. This is achieved by allowing simultaneous yet focused attention to be paid to all aspects of an impedance probe, i.e. hand-eye coordination of probe positioning, while aurally monitoring the feedback, instead of the common practices/methods where eyes have to be re-focused on visual feedback devices. The use of an alternating signal allows “through” comparison, where multiple components some of which are impervious to static signal, contribute to overall impedance. The device can be used to inject and/or detect/trace the presence of an audio signal in an active circuit. With the aid of transducers, this Device may be used with other forms of energy.

Abstract: The gas sensor may be an apparatus for sensing a proportion of a gas in a gas mixture. A gas sensor may have a sampling element slidably engaged with a sensor element. The sensor element may have a sensing chamber therein with an inlet passage and an outlet passage formed in the sensor element wherein the inlet passage and the outlet passage may be in communication with the sensing chamber and externally to the sensor element. A first detector may be positioned in the sensing chamber with a first pair of external contacts passing through the sensor element terminating externally thereto. The sensor element may have a reference chamber therein with a second detector positioned therein and a second pair of external contacts passing through the sensor element terminating externally thereto. The sampling element may have a sample chamber therein with the sensor element forming a portion of the sample chamber.

Abstract: A current comparator technique is applied to four-terminal resistance measurements for obtaining a highly accurate AC resistance bridge at power frequencies of 50 Hz to 60 Hz. Active circuits are used to establish equal voltage drops between the potential terminals of the two resistances being compared. The bridge is suitable for measuring resistances from 10 &mgr;&OHgr; to 100 k&mgr;&OHgr;. A cascading technique using two two-stage current transformers provides extension of the ratio range to 100,00,000 with a maximum applied current of 10,000 A. The bridge features measurement with a resolution of 0.1×10−6. The total combined uncertainty (2&sgr;) of the bridge including the range extenders, at power frequencies, is estimated to be less than 5 &mgr;&OHgr;/&OHgr;.

Abstract: An ASIC (14, 14′, 14″) conditions two independent outputs (VINM, VINP) of a full Wheatstone piezoresistive bridge (12) in separate conditioning paths. Each path is provided with a bridge supply voltage (VHB1, VHB2) 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 (U1, U2) 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 (U2) in one conditioning path of one half bridge is connected to the input of an amplifier (U4) 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.

Abstract: An ASIC (14, 14′, 14″) conditions two independent outputs (VINM, VINP) of a full Wheatstone piezoresistive bridge (12) in separate conditioning paths. Each path is provided with a bridge supply voltage (VHB1, VHB2) 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 (U1, U2) 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 (U2) in one conditioning path of one half bridge is connected to the input of an amplifier (U4) 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.

Abstract: A probe is disclosed which is suitable for use with an apparatus for monitoring the corrosion of a material by accurately measuring changes in the resistance of an exposed element (101) in relation to a reference element (103). The two elements are electrically connected in series via a bridge (131). The elements are formed from the same piece of material divided along an elongate slot (167) and are proximate to one another so that the temperature difference between them is kept to a minimum. This prevents false indications of corrosion by ensuring that the temperature coefficient of the resistivities is the same in both elements. The reference element (103) is covered with a corrosion-resistant layer. (113). This layer (113) is preferably as thin as possible and also a good thermal conductor to further ensure equal temperature of the reference (103) and exposed (101) elements.

Abstract: A stabilized fluid conductivity measurement system includes a threaded metal housing with an inner portion having two probes for contacting the fluid to be measured and having an outer portion in which electrical circuitry is mounted. The circuitry includes a balanced square wave generator providing excitation to a modified Wheatstone bridge, including first and second input excitation terminals, and first and second output terminals. Fixed resistances may be located in 3 arms of the Wheatstone bridge, and the fourth arm may have two resistances with an intermediate tap; and one of the two probes is connected to this tap while the other probe is connected to one of the input excitation points.

Abstract: A current comparator technique is applied to four-terminal resistance measurements for obtaining a highly accurate AC resistance bridge at power frequencies of 50 Hz to 60 Hz. Active circuits are used to establish equal voltage drops between the potential terminals of the two resistances being compared. The bridge is suitable for measuring resistances from 10 &mgr;&OHgr; to 100 k&mgr;&OHgr;. A cascading technique using two two-stage current transformers provides extension of the ratio range to 100,00,000 with a maximum applied current of 10,000A. The bridge features measurement with a resolution of 0.1×10−6. The total combined uncertainty (2&sgr;) of the bridge including the range extenders, at power frequencies, is estimated to be less than 5 &mgr;&OHgr;/&OHgr;.

Abstract: The output of a preamplifier is communicated to an active feedback circuit which drives the primary of a balancing transformer the secondary of which is connected in series with an impedance under test (IUT), the terminals of the series connection are communicated to respective differential inputs of the preamplifier. The feedback circuit automatically drives the preamplifier input toward balance, balance being achieved when the signal across the secondary equals the signal across the IUT in magnitude but opposite in phase. A DC blocking circuit is interposed between the series connection and the preamplifier for blocking preamplifier bias current from loading and heating the IUT. At balance an active equalizing transfer function circuit nulls any potential across the blocking circuit.

Abstract: A circuit capable of detecting natural gas at a wide range of concentrations is disclosed. The gas detection circuit includes a catalytic Wheatstone bridge circuit and an analyzing Wheatstone bridge circuit. A circuit for detecting natural gas, which includes placing a device containing the circuit described above in an area in which the air has a potential of containing natural gas, and monitoring the output signal for indications of the presence of natural gas is also disclosed.

Abstract: A radio frequency bridge, useful for measuring complex values of an unknown impedance or associated complex reflection coefficient and VSWR value, which comprises an rf source, a novel asymmetrical bridge, a measuring device (comprising two logarithmic amplifiers, a difference amplifier and a phase detector), a computing device and a display or interface device. The complex impedance may be any two terminals of a general N-port network not to exclude an antenna with or without feed-line. The invention is more accurate than prior art when measuring complex impedance values having magnitudes from approximately five ohms to an upper value limited only by the dynamic range of the logarithmic amplifiers, normally greater than 4000 ohms. It has the great advantage of maintaining constant measuring accuracy over a wide measuring range and can be designed to operate over very wide bandwidths.

Abstract: Disclosed is a current sensing system for measuring the current flowing through a current sensing resistance. The system has a calibration resistance coupled to the current sensing resistance and a pair of input resistances each having a first end coupled to one of the ends of the current sensing resistance and a second end coupled to one of the ends of the calibration resistance. A voltage is created across the calibration resistance and the calibration resistance is set at a predetermined level to compensate for the current sensing resistance deviating from a reference value. The voltage is filtered and amplified to produce an output representative of the measured current.

Abstract: An electronic control for the operation of a beverage dispenser of the refrigerated ice bank type is shown. The control provides for reliable determinations of when ice production is needed and when it is not needed. A microprocessor receives information from an ice bank probe and from a temperature probe located within the ice bank. Data collected by the microprocessor from both the ice bank probe and the temperature probe is used to determine if the ice bank is either insufficient in size and should be increased or is of sufficient size such that the compressor can be turned off. A carbonator level probe is also shown and connected to the microprocessor.

Abstract: An in-range fault detection system for a full wheatstone bridge element (12) having piezoresistive elements (R1, R2, R3, R4) has bridge outputs (INP, INM) connected to measuring means in the form of a first circuit portion (13) to provide a common mode voltage (VCM). A second circuit portion (14) is used to provide a centering voltage (C*VBRG) equal to the common mode voltage at the time of sensor calibration and a third circuit portion (15) is used to provide a small window voltage (W*VBRG) which is a fraction of bridge voltage. The value (W*VBRG) is subtracted from (C*VBRG) at a first summing circuit (SUM1) and added to (C*VBRG) at a second summing circuit (SUM2) and the results are each compared to the common mode voltage by comparators (Q1, Q2) which are then determined to be within or without a window of valid values by an OR gate (Q3).

Abstract: A magnetic oxygen analyzer which employes a detector comprising a magnetic pole, heat generator arranged in a non-uniform magnetic field where the intensity of a magnetic field produced by the magnetic pole varies, and a magnetic wind sensor disposed to not be affected by heat produced by the heat generator. A change in electrical resistance of the sensor, caused by change in magnetic wind strength, is detected as the oxygen concentration of a mixed gas. The magnetic wind is caused by the magnetic field produced by the magnetic pole and by heat produced by the heater and is related to the oxygen concentration of the mixed gas exposed to the analyzer. Advantageously, the analyzer of the invention provides improved signal to noise ratio, is immune to ambient temperature, and eliminates the need for precise temperature control.

Abstract: A position sensor and a method for sensing a position of a moveable member includes at least first and second deflectable members arranged so as to allow the moveable member to pass therebetween and cause the at least first and second moveable members to deflect in proportion to the position of the moveable member relative to the first and second deflectable members. In one example of the present invention, the deflectable members are cantilever-mounted members extending in generally the same direction. The amount of resultant deflection is measured by any suitable means. For example, each deflectable member may have a Wheatstone bridge provided thereon acting as a strain gauge in a known manner, such that the strain detected is proportional to the amount of deflection. In a particular example of the present invention, some of the elements of a first Wheatstone bridge are provided on the first deflectable member and some are provided on the second deflectable member.

Abstract: Detection of excessive negative offset of a condition responsive sensor such as a pressure responsive full Wheatstone bridge element (10) 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 (Q1) the signal (Vx) with a reference voltage (VREF1) 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.

Abstract: A pressure detecting bridge circuit produces a sensor signal Sd. A temperature detecting bridge circuit produces a temperature signal St. A reference voltage generating circuit produces a reference signal Sa. An analog multiplexer processes these signals Sd, St and Sa in a time-divisional manner. A differential amplification circuit and an A/D conversion circuit are commonly used to obtain the digital data corresponding to the sensor signal Sd, the temperature signal St and the reference signal Sa. The temperature detecting bridge circuit includes reference resistance elements. By adjusting the design resistance values of the reference resistance elements, the variation width of the sensor signal Sd in a pressure measuring range of the pressure detecting bridge circuit is substantially equalized in advance with the variation width of the temperature signal St in a temperature measuring range of the temperature detecting bridge circuit.

Abstract: According to the invention, an AC-signal is superimposed to a signal on the two lines to be monitored. A signal difference between the signals on each line is compared with the superimposed AC-signal. A short circuit between the two lines to be monitored can thus be detected when the superimposed AC-signal is not present in the signal difference. The frequency of the AC-signal is preferably selected as half of the sampling frequency of a subsequent sampling means. In a measuring bridge, the short circuit detection unit is coupled to a first and a second measuring point of the bridge.

Abstract: Monitoring of the function of a symmetrical sensor bridge circuit is performed in that the signal from the positive or negative half-bridge is subtracted from half the bridge supply voltage (V.sub.s /2) in a summing member (2) and is subsequently amplified by an amplifier (3) in such a way that it corresponds to the full bridge signal (V.sub.in). The full bridge signal (V.sub.in) is compared with the amplified difference signal in a comparator (5). If the difference signal deviates in an unacceptable manner from the full bridge signal, the comparator switches an alarm signal on the output signal (6) of the sensor, so that this output signal is placed into a range which lies outside of the normal operational range of the sensor.

Abstract: Sensors for measuring the flow rate of a fluid and for monitoring heat transfer. An induction-heated temperature-responsive sensor in contact with and cooled by the fluid, changes temperature in proportion to the quantity of heat removed by the fluid thereby providing a basis for determining flow rate or heat transfer. A flow modulation method and apparatus for improving the precision of flow rate measurement is also presented.

Abstract: The circuit for feeding a Wheatstone Bridge (DMS 1 . . . DMS 4) with a rectangular waveform alternating voltage which is derived from a single DC reference voltage, consists of a first operational amplifier (V 1) whose positive input is connected to the DC reference voltage and whose negative input is connected via the switches (S 5 and S 6) alternately to the one (A) or to the other (B) feed point of the bridge, and a second operational amplifier (V 2) whose positive input is connected to ground potential and whose negative input is connected to one measuring input (C) of the bridge. The outputs of the two operational amplifiers (V 1 and V 2) are connected via the switches (S 1 . . . S 4) alternately to the one (A) and to the other (B) feed point of the bridge, and the output signal is taken off at the second measuring output (D) of the bridge.

Abstract: A circuit for a combustible gas sensor comprising: a bridge circuit having first and second legs; a first node at a first midpoint in the first leg of the bridge circuit; a second node at a second midpoint in the second leg of the bridge circuit; a first temperature responsive resistive sensor element coupled between the first node and a bottom of the bridge circuit and located in a flow of combustible gas; a second temperature responsive resistive sensor element coupled between the bottom of the bridge and ground and located in the flow of combustible gas; and a voltage control circuit coupled to the first and second nodes and to the top of the bridge circuit for maintaining closed loop control of first and second node voltages at the first and second nodes by varying a bridge voltage at the top of the bridge circuit wherein one of the first and second sensor elements includes a catalyst for stimulating reactions of reactive constituents in the flow of combustible gas.

Abstract: The present invention, generally speaking, provides for highly accurate correction of a sensor output using circuitry that is compact and inexpensive. In accordance with one embodiment of the invention, an output signal of a sensor having a sensitivity that varies as a function of temperature and that includes resistors connected to form a bridge is corrected by, first, modeling the sensitivity of the sensor using an expression that is the ratio of two polynomials; applying a voltage across the bridge; and controlling the applied voltage as a function of temperature substantially in accordance with the inverse expression.

Abstract: A bridge circuit monitoring apparatus which can accurately detect a fault in a bridge circuit of a sensor circuit even when multiple faults occur. Changes in the imbalance output signal of a bridge circuit (11) are monitored with a first window comparator (WC1), while changes in the bridge circuit (11) power source current, which does not require amplifying, are monitored with a second window comparator (WC2). At the time of an output of logic value "1" indicating that the monitoring outputs are both normal, an output of logic value "1" indicating that the bridge circuit (11) is normal is generated from an AND gate (13).

Abstract: For determining the air mass flow in the intake pipe of an internal combustion engine by means of an electrical bridge, normally the current flowing through the current measurement resistor when balancing the bridge is evaluated as an indirect measure of the air mass flow. The primary measured quantity for the air mass flow is, however, the power converted at the air flow measurement resistor around which the air flows so that the indirect measurement always includes an error. To reduce this measurement error, the invention utilizes the evaluation of the sum of the voltage across the current measurement resistor and the voltage or a partial-voltage across the air flow measurement resistor as a measure of the air flow.

Abstract: Detector and method for detecting the presence of a liquid, such as water dew or of ice, or for detecting a change of phase in liquid, based on a change in an electrical resistance. The detector comprises a substrate onto whose face one or several resistor patterns are applied. For detecting the presence of a liquid or ice or equivalent by a change in the detector resistance, a low-mass detector resistor pattern is applied onto a substrate out of such a metal or equivalent as has a considerable dependence on temperature. On the substrate, there are contact patterns that feed a short pulse of electric current to heat the detector resistor as a short pulse, the presence of a liquid or ice and or a change of phase being detected by the change in resistance taking place during the short pulse. The thickness of the metal film in the resistor pattern (15) of the detector resistor (R.sub.det) is, as a rule, chosen as s<1 .mu.m.

Abstract: A differential voltage monitor is shown using a resistive bridge to produce a sample value representing that differential voltage. A portion of the resistive bridge is located on an IC and a portion is external to the IC. The object is to compare the differential voltage with a reference, producing a logic signal at a threshold level. The threshold level serving as a reference and the sample valve representing the differential voltage are made to be equally dependent on the bridge components located on the IC. In this way, any changes in the IC located bridge resistors compared to the bridge resistors located outside the IC are prevented from affecting the measurement.

Abstract: A method for measuring the degree of planarity in an integrated circuit includes depositing, onto a dielectric layer to be measured for planarity, a predetermined measure path of a conductive film and measuring the electric resistance of said measure path. The resistance of such a measure path is minimal where the surface on which it has been deposited is perfectly planar, and increases with the surface deviation from perfect planarity. An integrated circuit containing a measurement portion of conductive film and a reference portion of conductive film is described.

Abstract: An analog input apparatus comprises bridge measuring devices 11 and 31 connected to a bipolar voltage power supply 5, analog multiplexers 18, 19, 38, and 39 responsive to an output level of an oscillator 4B for switching a polarity and outputting two outputs of each of the bridge measuring devices 11 and 31, amplifiers 12 and 32 for amplifying bipolar outputs provided through the analog multiplexers 18, 19, 38, and 39, and an analog-to-digital converter 2 for converting outputs of the amplifiers 12 and 32 into digital form and outputting the resultant digital values.

Abstract: An analog input method comprises the steps of correcting a measured value with the digital value output when voltage at either middle point of a bridge circuit is fed into both input terminals of a differential analog amplifier or feeding two middle-point voltages of a bridge circuit into input terminal of an analog amplifier in order and providing a measured value based on the difference between the digital values output from the analog amplifier.

Abstract: The output of a bridge measurement circuit is sampled at a time when there is no desired, or expected, bridge output signal, and a balance voltage applied to the bridge measurement circuit is automatically adjusted such that the sample bridge output signal is equivalent to a reference output signal. After the bridge is balanced, the balance voltage is automatically modified by a calibration voltage calculated to provide a known change in the sample bridge output signal, and the sample bridge output signal is compared to a reference output to automatically check the bridge measurement circuit gain. The balance voltage may be automatically modified by multiple calibration voltages, and the sample bridge output signal provides an indication of the linearity of the amplifier gain. The sample bridge output signal is monitored after a change in the balance voltage to automatically provide an indication of the bridge measurement circuit filter cutoff frequency.

Abstract: A constant current loop measuring system measures a property including the temperature of a sensor responsive to an external condition being measured. The measuring system includes thermocouple conductors connected to the sensor, sensing first and second induced voltages responsive to the external condition. In addition, the measuring system includes a current generator and reversor generating a constant current, and supplying the constant current to the thermocouple conductors in forward and reverse directions generating first and second measured voltages, and a determining unit receiving the first and second measured voltages from the current generator and reversor, and determining the temperature of the sensor responsive to the first and second measured voltages.

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 semiconductor sensor has piezo resistor elements formed in deformable semiconductor portions for forming a Wheatstone bridge circuit, and a fault detecting circuit is associated with the Wheatstone bridge circuit for producing a warning signal indicative of occurrence of a fault in the Wheatstone bridge circuit, wherein the fault detecting circuit has two pairs of window comparators independently monitoring two output nodes of the Wheatstone bridge circuit to see whether or not the voltage level at each of the output nodes ranges between the upper limit and the lower limit of a normal voltage range so that a destruction of one of the piezo resistor elements is detectable.

Abstract: A method and apparatus for measuring mass flow rates and other characteristics of a fluid in a large conduit uses a sensor circuit having a heater/thermometer, a reference resistor, and a thermometer resistor arranged in four-wire network to enable measurement of all characteristics of the resistor network. That sensor circuit is preferably mounted on an interior wall surface of a support tube. A plurality of such support tubes, each having a plurality of sensors within the support tube, are mounted in an array in the cross section of the duct. A cleaning plate for cleaning the exterior surface of the support tube permits calibration of the network while cleaning. A program for using the circuit to calculate values of interest and to display desirable output data is also disclosed, as is a program for controlling the cleaning/calibration cycle.

Abstract: A superconducting magnet includes a superconducting coil, an inner tank for containing the coil, a shield plate for covering the inner tank, and an outer tank for accommodating the superconducting coil, the inner tank and the shield plate. The inner tank is supported on the outer tank by a load support member and the outer tank forms a vacuum vessel. At least one of the inner tank, the load support member, the shield plate and the outer tank includes a detection arrangement for detecting abnormality and/or deterioration of the inner tank, load support member, shield plate and outer tank associated with the respective detection arrangement.

Abstract: A constant current loop measuring system is provided for measuring a characteristic of an environment. The system comprises a first impedance positionable in the environment, a second impedance coupled in series with said first impedance and a parasitic impedance electrically coupled to the first and second impedances. A current generating device, electrically coupled in series with the first and second impedances, provides a constant current through the first and second impedances to produce first and second voltages across the first and second impedances, respectively, and a parasitic voltage across the parasitic impedance. A high impedance voltage measuring device measures a voltage difference between the first and second voltages independent of the parasitic voltage to produce a characteristic voltage representative of the characteristic of the environment.

Abstract: An analog input apparatus comprises bridge measuring devices 11 and 31 connected to a bipolar voltage power supply 5, analog multiplexers 18, 19, 38, and 39 responsive to an output level of an oscillator 4B for switching a polarity and outputting two outputs of each of the bridge measuring devices 11 and 31, amplifiers 12 and 32 for amplifying bipolar outputs provided through the analog multiplexers 18, 19, 38, and 39, and an analog-to-digital converter 2 for converting outputs of the amplifiers 12 and 32 into digital form and outputting the resultant digital values.

Abstract: A humidity detection circuit includes a bridge circuit containing temperature sensing elements. The bridge circuit is connected in series to a current limiting resistance, a current controlling element and a power supply. There is a set of resistances arranged in parallel with the current limiting resistor and the bridge circuit. A voltage comparing circuit is operatively connected to the bridge circuit the current limiting resistance and the set of resistances. A control section is provided to detect the potential of a junction between the bridge circuit and the current limiting resistance. Based upon the detector potential, the humidity detection circuit changes resistance value of a resistor in the set to an optimal level so that temperature drift does not occur.