Abstract: A linearizing circuit is provided for a non-destructive testing instrument having circuit means developing a DC voltage having a non-linear relationship to units of measurement or of conductivity or some other characteristic measure. A plurality of linearizing stages are provided each including an adjustable resistance connected between a reference voltage source and an output line when the potential of the output line is between the reference voltage and one limit of the DC voltage. Preferably, an analog switch is provided in series with the adjustable resistance and is controlled from an operational amplifier, with a second operational amplifier being provided having an output connected through the analog switch and the adjustable resistance to the output line. The circuit is very accurate and reliable and is readily adjusted by a method wherein the resistances are adjusted in accordance with reference voltages in a certain sequence to obtain accurate adjustment with no juggling operation.

Abstract: A light signal entering a photo-electric converter means is interrupted at a certain interval of time. An electrical signal produced from the photo-electric converter means, after a predetermined amount of electrical signal is added to it, is A-D converted. The difference between the digital signal associated with the interruption of light to the photo-electric converter means and the digital signal associated with non-interruption of light to the photo-electric converter means is produced, which difference is proportional to the incident light signal. Even when the light entering the photo-electric converter means is very weak, the fact that a predetermined amount of electrical signal is added contributes to A-D conversion of good linearity. Even very weak light is thus A-D converted accurately. Noises and undesirable DC signal components contained in the two types of digital signals are offset by production of the difference.

Abstract: The accuracy and linearity of a moving-coil instrument is determined by the choice of materials, the design and the production tolerances.The invention proposes to make an inaccurate moving-coil meter with a non-linear relationship between meter current and meter deflection accurate and to provide it with a linear scale by adding a diode-resistor network and adjusting said network so that said accurate linear scale is obtained. Direct current or direct voltage inputs are then possible. An inexpensive accurate, analog indicating instrument is then obtained which may be used in a variety of measuring systems.

Abstract: Electrical noise is suppressed on an input signal by squaring the input signal and any noise thereon, removing the sinusoidal terms in the squared output (as by averaging), subtracting the d.c. noise component, and taking the square root of the remainder, so as to produce an r.m.s. dependent, substantially noise free output. If desired, the noise suppression circuitry may be combined in a low signal measuring instrument in which the input signal is repetitively sampled and freed of noise in the manner described, the output then being measured on a d.c. meter.

Abstract: An arrangement for the determination of the effective value and/or the performance or power and, for example, also the cross-power of electrical signals, in particular those Doppler signals which are received in ultrasonic-Doppler blood flow measurement. The arrangement includes an amplifier for the present electrical signal regulatable in amplification which, on the one hand, is connected into a control loop or circuit for regulating the degree of amplification for the purpose of producing constant amplifier power outputs and, on the other hand, connected into a measuring circuit for determination of the degree of amplification which adjust itself at the current power constant-regulation of the amplifier.

Abstract: A circuit arrangement for linearizing the output signal of a measuring sensor by comparing this output signal with a periodically repetitive signal which represents the measurement characteristic to be linearized. Upon equality of the compared signals, the instantaneous value of a periodically repetitive second signal, which is a linear function of time, is transmitted to form the linearized measurement signals. According to a preferred embodiment, the periodically repetitive signals are produced by digital devices.

Abstract: The precision measuring amplifier includes one or more amplifiers, a number of fixed attenuators, a RMS detector and a logarithmic converter for converting the output of the RMS detector to a logarithmic value. A number of fixed voltage sources each providing a voltage precisely related to the attenuation of a corresponding attenuator, are selectively coupled to a summing amplifier to which the logarithmic converter output is also connected. The number of attenuators connected either manually or automatically into amplifier apparatus at one time is dependent on the input signal level, and for every attenuator connected into the amplifier apparatus, a voltage source is connected to the summing amplifier to provide an output signal proportional to the logarithm of the RMS value of the input signal.

Abstract: An inner magnet type movable coil instrument comprises a cylindrical permanent magnet magnetized to axis-symmetrically form a pair of opposite magnetic poles in a direction to the axis of the magnet; a pair of arcuate magnetic plates made of soft iron and bonded to the opposite side surfaces of the cylindrical permanent magnet with each magnetic pole located at a central line of the magnetic plate; a semicylindrical yoke made of soft iron and secured to one side surface on which it intersects orthogonal to the opposite magnetic poles, said yoke being arranged coaxial with the permanent magent and having sections inclined in the same direction to the axis of the yoke and confronting the magnetic poles of the permanent magnet; a movable coil rotatable coaxially of the permanent magnet and in a gap between the permanent magnet and the yoke; upper and lower bearing members formed integral with the yoke and journalizing the movable coil therein; control spring means mounted on the movable coil; and a pointer.

Abstract: In combination with a meter movement having a pointer movable over a variable value indicating scale having numbered variable value indicating marks forming respective scale segments having substantially different compression or expansion ratios and representing progressively increasing variable values over the entire extent of said segments, a meter control circuit comprising respective amplifiers for controlling the variation of pointer movement over said respective segments of said scale, each of the amplifiers being capable of producing an output which reaches a maximum possible output level when the signal fed to the input thereof is of a value which is to move the pointer of said meter movement to the uppermost point of the associated segment of the scale, means for summing the outputs of said respective amplifiers and feeding the same to said meter movement.

Abstract: Improvements in a digital echo canceller utilizing pseudo-logarithmic coding are disclosed which reduce the complexity and cost while improving the performance of the echo canceller. Specifically, there is disclosed an improved analog to pseudo-logarithmic converter, a first and a second embodiment of an improved pseudo-rms to dc converter, an improved .phi.(x) function generator, and an improved error detector.

Abstract: An RMS circuit comprising a logarithmic amplifying circuit, a fullwave rectifying circuit for subjecting an output from the logarithmic amplifying circuit to fullwave rectification, and a smoothing circuit for smoothing an output signal from the fullwave rectifying circuit, wherein the logarithmic amplifying circuit is provided with an operational amplifier whose noninverting input terminal is grounded and whose inverting input terminal is connected to a signal source; a first npn transistor whose collector is connected to the inverting input terminal of the operational amplifier and whose base is grounded; a first diode whose anode is connected to the emitter of the first npn transistor and whose cathode is connected to the output terminal of the operational amplifier; a second diode whose anode is connected to the output terminal of the operational amplifier; and a third diode whose anode is connected to the cathode of the second diode and whose cathode is connected to the noninverting input terminal of the

Abstract: A double beam optical null spectrophotometer having sample and reference optical beam paths, a detector common to both paths, and an attenuator feedback loop from the detector for adjusting the position of an optical attenuator in the reference beam path to balance the energy in the two paths. The slider of an attenuator transmitting potentiometer follows the position of the optical attenuator and a signal level sensitive impedance network connected to the slider calibrates the potentiometer such that an output signal therefrom indicates the true transmittance of a sample in the sample beam path over a range of transmittance values from zero to one hundred percent transmittance.

Abstract: A system for deriving a voltage which is a logarithmic function of peak value of an audio signal, in which the audio input signal is amplified by means of an operational amplifier having bipolar feedbacks through a pair of oppositely poled rectifying junction devices operating over logarithmic portions of their response characteristics, the output of the operational amplifier being applied in opposite polarities to a second pair of rectifying junction devices to rectify a bipolar signal applied thereto, and to control current flow to a storage capacitor, the second pair of devices having a common load which provides a constant current source for slow charge of the storage capacitor in one sense, the second pair of devices providing rapid discharge paths in the opposite sense. In one embodiment either or both pairs of rectifying junction devices can be transistors.

Abstract: A level meter circuit for indicating a level of input signal over a wide dynamic range, comprising an amplifier of relatively high amplification factor having input terminal means to which an input signal is supplied and output terminal means to be connected to a level meter and negative feedback means including a feedback resistance to feedback an output signal from said output terminal means to said input terminal means, said negative feedback means characterized by further including non-linear impedance means connected in parallel to said feedback resistance and having such characteristics that when said output signal from said output terminal means is below a predetermined level said non-linear impedance means has a substantially infinite impedance and when said output signal from said output terminal means reaches said predetermined level said non-linear impedance means has a predetermined impedance.

Abstract: An arrangement for the determination of the effective value and/or the performance or power and, for example, also the cross-power of electrical signals, in particular those Doppler signals which are received in ultrasonic-Doppler blood flow measurement. The arrangement includes an amplifier for the present electrical signal regulatable in amplification which, on the one hand, is connected into a control loop or circuit for regulating the degree of amplification for the purpose of producing constant amplifier power outputs and, on the other hand, connected into a measuring circuit for determination of the degree of amplification which adjust itself at the current power constant-regulation of the amplifier.

Abstract: The differential thermal wattmeter for the ac/dc transfer of power includes a differential thermal converter as a "sum and difference" multiplier, with both ac and dc voltage and current signals simultaneously applied to both heaters. DC feedback to the current input speeds up the response and maintains thermal balance between the heaters, so that the output meter becomes a null indicator. This reduces and can eliminate the need for quadratic response. The requirement for exact matching of the thermal converters is also eliminated by effective interchange of the heaters.

Abstract: A checker for a.c. and d.c. voltages in the range of 3 to 250 or more volts in which a single light emitting diode serves as an indicator for all voltages and the current through the light emitting diode is controlled by a transistor and a zener diode. The tester indicates a.c. or d.c. and polarity of d.c. voltages.

Abstract: A scale modifying circuit for providing either expanded or compressed scale readings on a conventional electrical indicating instrument. The device includes a pair of input terminals adapted to be connected to a source of voltage to be monitored or measured, a voltage responsive network connected with one of said input terminals for supplying output voltage to output terminals of the device, and amplifier means driven from the input terminals and having an output connected to supply a driving voltage to at least one of the output terminals. Expanded scales (or compressed scales) can be provided at the lower, middle, or high end of a particular range of voltages being monitored, or at intermediate points. This results in higher resolution over the expanded scale portion, together with improved accuracy. An illustrated embodiment of the invention embraces a voltage-limiting diode, to effect a cut-off of an ascending applied voltage.

Abstract: An automatic gain control circuit functions to adjust the magnitude of an input signal supplied to a measuring circuit to a level within the dynamic range of the measuring circuit while a log-ratio circuit adjusts the magnitude of the output signal from the measuring circuit to the level of the input signal and optimizes the signal-to-noise ratio performance of the measuring circuit.

Abstract: Disclosed is the physical construction and electrical control circuit of a fault indicator designed to provide a watertight structure for the indicator. One face of the indicator is visible through the sealing apparatus, the sealing apparatus enclosing the structure on all sides other than the indicator face side. The indicator is capable of being submerged and will withstand a water pressure of 8 psig to meet specifications established by electric utilities. The electrical control circuit normally causes the transformer to operate below its saturation level resulting in quick response to changes in input current, and providing improved temperature stability of the control circuit.

Abstract: A digital display electronic meter apparatus is disclosed which is capable of displaying amplitude ratio measurements directly in decibels over its entire amplitude operating range.

Abstract: A digital voltage level measuring device includes an amplifier having a capacitive feedback the output voltage of which is brought to a value dependent upon the integration result reached within a given interval of time of a voltage to be measured. After disconnection of the voltage which is to be measured, the output voltage is fed back to the amplifier input. The interval of time from the beginning of the feedback phase until the reaching of a given voltage value by the exponentially changing output voltage is then digitally measured.

Abstract: The tester does not require any external power source as it derives its energy from the pulse being measured. It includes circuitry which produces a signal proportional to the energy without directly calculating the energy. This is accomplished by generating a current portional to E.sup.2 with a diode network and then integrating the current in a capacitor thus indirectly measuring the true energy. The results are read directly upon a linear meter or can be connected to an oscilloscope or the like for inspection or recording. A bridge rectifier can be used so that the circuit is responsive to both polarities of input pulse or it can be made responsive only to the unipolar signal.

Abstract: The disclosed circuit provides a wideband, wide-range logarithmic responding voltmeter particularly suitable for use as a transducer analyzer. The circuit includes an input for receiving a given A.C. input signal which can vary within a 100 db dynamic range. The input signal is coupled to a buffer amplifier the output of which is capacitively coupled to a logarithmic converter. The converter includes an operational amplifier and provides an A.C. output signal which is proportional to the logarithm of its A.C. input signal. The open loop gain of the operational amplifier is utilized to provide the A.C. output signal. The output signal of the converter is capacitively coupled to a precision AC/DC converter which rectifies and filters the output signal to provide a D.C. output voltage the level of which is, therefore, also proportional to the logarithm of the given A.C. input signal within its 100 db range. The D.C.

Abstract: An intermodulation distortion analyzer generates two pairs of sinusoidal test tones to serve as a test signal for the channel under test. The two pairs of tones simulate two respective noise band test signals but eliminate the long time averaging required for measurements when noise bands are used. A highly linear AGC circuit employs sampling at an output-controlled duty cycle to maintain a constant reference level for the analyzer. This reference level permits automatic distortion measurements to be read out directly in db below the test signal. An RMS detector circuit for second order intermodulation products employs feedback control to maintain the input signal to a squaring circuit constant. Squaring of the constant level sinusoids produces RMS DC components which can be separated for direct measurement. A distortion circuit provides known levels of second and third order intermodulation in the test signal to permit accurate check out of the analyzer.

Abstract: A D.C. tachometer circuit comprising a non-linear D.C. tachometer which produces an output voltage having an A.C. ripple, a first current path from the D.C. tachometer including means for removing the D.C. component of the output voltage of the tachometer, means for inverting and isolating the A.C. voltage ripple, and means for eliminating drift and the D.C. level of the inverted and isolated A.C. voltage-ripple, means for mixing the original output voltage of the D.C. tachometer including the A.C. ripple and the inverted and isolated A.C. voltage ripple to establish a non-linear ripple-free output voltage, and means for linearizing the non-linear ripple-free output voltage.