Abstract: A thin film strain gage structure (10, 110) for measuring the strain of an inflectible element (12, 112) wherein the gage is formed on a surface (15, 115) of the element and includes a sensing resistance (16, 116) and an adjusting resistance portion (21, 121). Connecting taps are formed in relationship to the resistors to permit adjustment of the adjusting resistor values by suitable connection to selected ones of the taps. The adjusting resistance is preferably disposed adjacent the sensing resistance so as to be subject to similar ambient conditions. The sensing resistance may be provided in the form of a Wheatstone bridge circuit with the adjusting resistors connected in series with two legs of the bridge. Adjustment of the adjusting resistance may be effected selectively by shorting out portions thereof or by suitably connecting to different portions thereof.

Abstract: An automatic zero balance circuit for nulling the initial offset signal received from a test transducer. A quadrature oscillator powers a carrier transducer with the phase reference signal. A summing circuit receives the return signal from the transducer and sums it with two other signals. The resultant summation signal is divided into two components, the phase reference component and the quadrature reference component which are fed back into the summing circuit as the two other signals. The component values nullify the return signal thereby cancelling the initial offset signal.

Abstract: A strain measuring device using a Wheatstone bridge circuit. An excitation voltage changing switch switches from one excitation voltage to a different excitation voltage in accordance with a controlling circuit providing sequence operation of them and of other circuit elements to remove spurious components affecting the measurement of strain. Such spurious components include potential errors due to thermal electromotive force produced inside or outside said Wheatstone bridge circuit and sensitivity error due to drift voltage occurring in the driver circuit of the bridge current source. A comparator may be used to effect judgment of the amount of the measured value of the voltmeter, so that the controlling circuit causes excitation voltage changing switch to select only two excitation voltages out of at least three for switching no matter how many excitation voltages are provided for in the bridge current supply source.

Abstract: A force measuring device comprising a load receiving platform supported by a multiple bending parallelogram beam type load cell is provided with a plurality of electrical strain gages. Strain gage elements mounted on one of the beams are displaced toward one side of the beam and strain gage elements mounted on the other beam are displaced toward the other side of the other beam. An appropriate resistor network is connected to at least one strain gage on one or both of the beams to correct for either longitudinal or transverse displacement of the load on the platform. To correct for both transverse and longitudinal displacement of the load a resistor network is connected to each of three of the strain gages. Suitable procedures for determining the values of the resistor networks in combination with the above structure are included.

Abstract: A thin film strain gage structure (10,110) for measuring the strain of an inflectible element (12,112) wherein the gage is formed on a surface (15,115) of the element and includes a sensing resistance (16,116) and an adjusting resistance portion (21,121). Connecting taps are formed in relationship to the resistors to permit adjustment of the adjusting resistor values by suitable connection to selected ones of the taps. The adjusting resistance is preferably disposed adjacent the sensing resistance so as to be subject to similar ambient conditions. The sensing resistance may be provided in the form of a Wheatstone bridge circuit with the adjusting resistors connected in series with two legs of the bridge. Adjustment of the adjusting resistance may be effected selectively by shorting out portions thereof or by suitably connecting to different portions thereof.

Abstract: An RTD probe interface having a three-wire interconnection with a source excitation line, a source return line, and a sensed signal line, includes: an excitation signal source connected between the source excitation line and the source return line for providing an excitation current signal through the RTD; an amplifier having first and second signal inputs connected respectively to the source excitation line and the sensed signal line, for providing an output voltage signal at a magnitude proportional to the difference magnitude between the voltage signals present at the first and second amplifier inputs, and a bias signal source connected between the sensed signal line and the source return line for presenting a bias current signal to the sensed line, at a magnitude and phase equal to that of the excitation current signal, for providing equal line impedance dependent values in the voltage signals appearing at the first and second inputs of the amplifier.

Abstract: An improved surface acoustic wave sensor in which two surface acoustic wave arrays are disposed in predetermined overlapping relationship by the use of a sealing compound which both establishes a thin sealed cavity and spaces the two surface acoustic wave arrays apart a predetermined distance, thereby eliminating the need for spacing rings or the like.

Abstract: A transducer bridge circuit arrangement which may include a plurality of individual bridge circuits is improved by standardizing the source resistance and open circuit sensitivity of each bridge circuit in a group of such circuits. For this purpose a small resistor is connected in series with one or both output terminals of each individual bridge circuit, or resistors may be inserted in series with the bridge excitation terminals. Thus, the output signal sensitivity and source resistance are adjusted to a standard ratio value and the prior art adjustment for so-called corner sensitivity in electronic scales has been eliminated or at least substantially reduced where strain gauge load cells are employed in multiple transducer installations.

Abstract: A method of and apparatus for calibrating and providing an output from a strain gauge (1) is described. In the method and apparatus there is provided a constant-current source (10). Coupled to the current source (10) is an amplifier (12,13) for providing an output corresponding to the difference between the voltage drop across the strain gauge (1) and a reference voltage from a source (14). The reference voltage is used to adjust the current in the strain gauge (1) from the current source (10). After the current is adjusted, further changes in the voltage drop in the strain gauge (1) relative to the reference voltage is used for providing an output of the voltage difference relative to the reference voltage. The adjusting of the magnitude of the current from the constant-current source (10) is provided by a calibrate-and-zero sample and hold circuit (16) having a sample and hold period sufficient to reduce to negligible levels the effects of the dielectric absorption of an associated capacitive means (20).

Abstract: A semiconductor sensor configuration employs piezoresistors arranged in a bridge configuration. A memory has stored therein at predetermined locations, values indicative of error voltages associated with the particular bridge circuit due to undesireable variations of temperature and pressure. The bridge circuit is coupled to digital processing circuitry which serves to access the memory at desired locations to retreive the values stored and to process these values in order to compensate the output signal supplied by the bridge during operation to provide a compensated output signal truly determinative of the applied pressure as being compensated for the particular error signals as stored in the memory.It is also understood that the above described technique has applicability in compensating other sensor configurations which employ non-semiconductor strain gages.

Abstract: A shear transducer having two cylindrical bending beams with two full strain gage bridges so arranged to cancel acceleration induced by forces in the axis of interest.

Abstract: A piezoresistive differential pressure transducer in which the need for convoluted isolating diaphragms and oil fill is eliminated. The instrument as contemplated by the invention does not require O-ring seals or springs to provide over-pressure protection. The absence of convoluted diaphragms and oil minimizes inherent errors due to temperature variations and static line pressure effect.

Abstract: An embedded stress sensor gage for use in solid fuel rocket motors and the like consisting of a modified bridge circuit containing temperature sensitive resistive elements and a pair of series connected resistors coupled in parallel with the bridge. A comparison of the voltage at the midpoint of the series connected resistors and the output voltage of the bridge and the voltages at the active resistive elements provides information from which it is possible to determine the change in gage element resistance for each temperature and stress condition.