Abstract: An apparatus for sensing current in a switching device having resistive voltage-current characteristics includes a first and second power terminal (typically common or ground) for the application therebetween of an operating potential (or alternatively, power), an impedance connected between the first power terminal and a node, a switching device having its main conduction path connected between the node and the second power terminal for controlling the flow of current through the impedance, at least one sense device coupled to the node, operative to sense or divide the potential at the node to thereby provide a sensing potential, where at least one of the sense devices is switched only during at least a portion of the period when the switching device is turned on, and a voltage reference generating circuit operative to generate a reference voltage for comparison with the sensed potential.

Abstract: A method and apparatus for obtaining a voltage-isolated measurement channel in a measurement instrument is provided. An input signal is multiplied with a clock signal to obtain a modulated input signal that is coupled to an input winding of a balanced transformer. The modulated input signal is electromagnetically coupled from the input winding to an output winding. At the same time, the input winding and the output winding are voltage-isolated, meaning that the portion of the measurement channel coupled to the input winding is "floated" with the input signal whereas the remaining portion of the measurement channel is referenced to instrument ground. A sampling circuit coupled to the output winding samples the modulated input signal in the manner of a synchronous detector to extract the original input signal voltage which is provided to an analog to digital converter which generates the digital measurement values.

Abstract: A non-ferrous current sensor is used to continuously measure the charging current magnitude in step-graded foil and paper insulation systems used on high voltage measurement and control apparatus such as instrument transformers and on the condenser bushings of power transformers and circuit breakers. The low voltage measured signal is conditioned by an electronic circuit such that it modulates a DC signal in a system current control loop to provide continuous remote monitoring and alarm functions. Remote power is supplied to the sensor and conversion circuits through the current loop. Alarm level thresholds and alarm time delay are embodied in a control device which may be located in a remote location, away from the high voltage equipment. Step-graded insulation systems form a capacitively divided circuit between the high potential and ground. As the dielectric between the foil layers breaks down, the total capacitance of the insulation system increases, producing an increase in the charging current.

Abstract: Apparatus is disclosed for measuring the fundamental voltage, fundamental frequency and the fundamental voltage divided by the fundamental frequency of the output of a device, such as an inverter. Through the use of an isolation amplifier connected across the output of the inverter and proper component selection, the output signal produced by the isolation amplifier is representative of the fundamental voltage of the output of the inverter divided by the frequency of the fundamental voltage. The output signal from the isolation amplifier is converted into a pulse having a fixed width w, fixed height h and period 1/f to produce a signal representative of the fundamental frequency of the output of the inverter. The output signal from the isolation amplifier is also rectified and applied to a multiplier along with a signal having a fixed width w, height E.sub.in /f and period 1/f and then averaged to produce an output signal representative of the fundamental voltage of the output of the inverter.

Abstract: A phase modulated signal is split into quadrature components Savg+SaSin(.phi.(t)+kx(t)) and Cavg+CaCos((.phi.(t)+kx(t)). The average value for each signal is compared with the signal to produce a data bit whose meaning is that the average value was exceeded at a sampling instant. The bits at successive times (t.sub.0 and t.sub.1) are separated by an interval set by the Nyquist rate on the peak rate of change of the phase for the signal. Four bits at two sample times t.sub.0 and t.sub.1 are processed to determine the phase quadrants modulo 360 degrees to determine the direction of the phase change. The determination is used to produce a counter enable signal, counter direction control signal (up/down) and optionally an error signal if the phase change during one clock period is more than plus or minus one quadrant. A tracking counter counts the number of quadrants of change from those signals.

Abstract: A heterodyning lock-in amplifier in which the reference signal is shifted up in frequency (as in prior art designs), but then shifted back down in frequency prior to mixing with the input signal.

Abstract: An analog direct current to one MHz information channel is provided, with high acccuracy and 10K volt input-output isolation. The information channel has a voltage to current converter which receives the analog input signal, and whose output is modulated by a square wave generator and provided to a center tap of the primary winding of a transformer. On the output side, the secondary winding of the transformer provides the signal to a precision rectifier which recovers the analog input signal.

Abstract: A signal detector includes a signal input section, a detector, and a converter. The signal input section inputs a high frequency signal to be measured. The detector detects the high frequency signal to be measured input by the signal input section. The converter amplifies the output from the detector and includes a variable gain preamplifier which has a first gain higher than a linear gain when the detecting output is smaller than a predetermined value and a second gain lower than the linear gain when the detecting output is larger than the predetermined value. A cable line transmits an output from the variable gain preamplifier of the converter of the signal detector. A measuring equipment body includes a decoder and an analyzer.

Abstract: A circuit arrangement for detecting an input voltage comprises an oscillator responsive to the voltage, the oscillator including a pair of transistors (8, 9) connected as an astable multivibrator, each of the transistors having a load which comprises a primary winding (16 or 17) of a current transformer (T) and a low resistance proof resistor (12 or 13). A current flows through a secondary winding (18) of the transformer the amplitude of which current is proportional to the input voltage.

Abstract: An improved isolated analog sense circuit comprises a sensor for passively sensing voltages, a transformer, a capacitor, a clock signal generator, a switch, and a diode. The transformer has two windings, the first of which is coupled to the sensor with the transformer coupling the voltage to be sensed from the first winding to the second winding. The switch is coupled between the capacitor and the second winding, and is responsive to the clock signal generated by the clock signal generator. Operation of the switch causes the capacitor to charge up to a voltage representative of the sensed voltage. The diode is included in the sensor to prevent current flow in the first winding of the transformer when the switch is off.

Abstract: Process for the digitization and linearization of a quasi-sinusoidal periodic characteristic transducer and the corresponding apparatus.The process consist of measuring a variation (.DELTA..phi..sub.x) of a signal (.phi..sub.x) received by the transducer in accordance with the following operations:superimposing on the signal to be measured a first auxiliary periodic signal (.phi..sub.I) of frequency F.sub.I higher than the highest frequency of the range of the signal to be measured and of amplitude substantially equal to .phi..sub.o /2 and a second auxiliary signal constituted by a periodic linear ramp (.phi..sub.R) of a frequency f.sub.R well below F.sub.I and of amplitude .phi..sub.1, the transducer thus receiving a composite signal constituted by the signal to be measured, the first auxiliary signal and the second auxiliary signal;deducing from the signal supplied by the transducer, two periodic signal V.sub.C1 and V.sub.C2, of period .phi..sub.

Abstract: A test bench is designed to determine the transfer function of a radio link in terms of variations in amplitude and a group propagation time depending on frequency. A transmission section of the test bench comprises an oscillator delivering a pulse signal having a predetermined intermediate frequency, a generator generating an exploration signal having a predetermined low frequency and a marking pulse signal synchronous with the exploration signal, a summator summating the exploration signal and an analog signal into a wobbulation signal, a r.f. wobbulator controlled by the wobbulation signal for producing a wobbulated signal to be transmitted. In a receiving section of the test bench, an analyzer receives the wobbulated signal via said radio link to analyze parameters of the radio link, such as the link group propagation time.

Abstract: For measuring voltage sources with capactive internal impedance (Z.sub.G) the voltage source is connected to a charge amplifier (7) whose input capacitance comprises a vibrating capacitor (C(t)). The output of charge amplifier (7) is connected in series with negative feedback via a regulator to the input of the measuring circuit. The frequency response of this transmission line (7, PID) is designed so that a closed regulating circuit has a good follower behavior, at least up to signal frequencies corresponding to the exciting frequency of vibrating capacitor (C(t). The vibration of the capacitor causes an amplitude-modulated alternating signal with the voltage across said capacitor to appear at output (A). This signal is filtered out (13), amplified (15), and amplitude-demodulated (17). The demodulated signal is filtered, and supplied through a high-ohmage resistance (R) as a current to the current summation node of charge amplifier (7).

Abstract: A device for isolating an electrical instrument from an input voltage signal at a floating potential. The device includes a transformer with a center-tapped primary winding, a center-tapped secondary winding and a core magnetically coupling the primary and secondary windings. The input voltage signal is applied to an input terminal coupled to the center tap of the primary winding. A modulator circuit is connected to the primary winding for alternately applying the input voltage signal to opposite sections of the primary winding by means of FETs, or the like, isolated from a control circuit by a transformer, the control circuit alternately switching the modulator circuit at a suitable modulating frequency.

Abstract: The surface potential electrometer includes a reciprocating chopper, a measuring electrode on which a voltage is induced which is associated with the surface potential of a member to be measured, a shield member for shielding the measuring electrode and the chopper from electric field emanating from the member to be measured, and a driver for driving the chopper, thereby detecting the surface potential of the member in the form of an AC signal. The shield member is provided with an aperture for guiding the electric field emanating from the member to the measuring electrode.

Abstract: A device for isolating an electrical instrument from an input voltage signal at a floating potential. The device includes a transformer with a center-tapped primary winding, a center-tapped secondary winding and a core magnetically coupling the primary and secondary windings. The input voltage signal is applied to an input terminal coupled to the center tap of the primary winding. A modulator circuit is connected to the primary winding for alternately applying the input voltage signal to opposite sections of the primary winding by means of photo FETs or the like for alternately switching the modulator circuit at a suitable modulating frequency. A demodulator circuit is connected to the secondary winding for alternately connecting each end of the secondary winding to a common return point to demodulate the output signal from the center tap of the secondary winding by means of FETs or the like.

Abstract: An improved meter for measuring RF power. The RF power is applied to thermocouple means which transforms the RF power into a low level d.c. signal which then passes through a chopper stage that is driven by a clamped sinusoidal input. The output of the chopper stage includes periodic pulses with a prescribed pulse spacing: pulse duration ratio, the pulses being passed through a band-pass filter at a harmonic of the chopper drive signal. The filtered signal, which is also amplified, undergoes synchronous detection with a tri-level square-wave signal which is centered in phase relative to the amplified, filtered signal when the two signals are in phase. The power meter measurements adjusted for zero drift and calibration drift by a microprocessor; based on zero measurements and calibration measurements made before and after an RF measurement is made. Measurements are stored and processed digitally to enhance accuracy.

Abstract: A pulse width modulator for an electronic kilowatt-hour meter includes an integrator having its inputs connected to a square wave clock signal and a sine wave signal proportional to the time derivative of current on the metered circuit. A plurality of series-connected inverters are connected to the output of the integrator to function as a comparator which generates a pulse width modulated signal having a duty cycle proportional to metered current. A negative feedback path including a low pass filter is connected between the output of the last inverter and an input to the integrator to compensate for errors produced by the integrator and inverters, thus permitting the use of low cost inverters fabricated on an integrated circuit.

Abstract: An electrostatic voltage sensor which includes a surface acoustic wave propagating medium and transmitting and receiving transducers coupled to the medium. The voltage sensor is provided with a separate voltage collecting member different from the electrode for applying a voltage or electric field, and the voltage obtained in the voltage collecting member is varied by a predetermined frequency for being applied to the electrode so as to detect external voltage by the variation component of the oscillating frequency.

Abstract: An FM transmitter linearity test equipment includes an amplitude modulation generator signal source producing an amplitude modulated signal of known varying amplitudes changing at a known rate and a demodulator for demodulating the resulting frequency FM signal from the transmitter. The test equipment also includes a commutating filter operating at said known rate and which is receptive of the demodulated signal for producing a signal of varying amplitude which is compared with the signal produced by the signal source to determine the linearity of the FM transmitter.

Abstract: A power level measurement system includes a power level sensor having a linear response to power level variations for power levels below a predetermined level and a non-linear response above the predetermined level, a DC amplifier and linearity compensator for measuring power and amplitude levels above the predetermined power level, a switched amplifier circuit containing a DC to AC converter circuit, an AC amplifier and a detector for measuring power levels below the predetermined level, means for determining whether the power level of the high frequency signal is above or below the predetermined power level and for accordingly selecting either the DC amplifier or the switched amplifier system in accordance with this power level, and display means for displaying the output from the selected amplifier system.

Abstract: An amp-hour meter for a load driven by direct current, such as an electric vehicle, comprises a modulator connected across a resistor in series with the load for amplitude-modulating a pulse train from a multivibrator translated by a demodulator into a unipolar voltage varying with the load current. A sampler converts this voltage into a train of output pulses, generated at a rate proportional to the voltage level, whose count is numerically displayed as a measure of current consumption. The multivibrator, the demodulator, an intervening amplifier, the sampler and the display unit are serially energized with stabilized voltage and reduced current via a supply network connected across the load, this network including a ballast lamp in series with a Zener diode.

Abstract: Apparatus for measuring a resistor in function of the amplitude of a direct current or the frequency and the amplitude of an alternating current. When the direct current equipment of this apparatus is used, the direct current signal flowing through the resistor is generated from an adjustable direct current generator and produces between terminals of the resistor a direct voltage signal which is chopped and amplified into a recurrent rectangular signal having a predetermined frequency and an amplitude proportional to the resistance value of resistor and included within a predetermined measurement interval. When the alternating current equipment of this apparatus is used, a first alternating current signal flowing through the resistor is generated from an adjustable frequency generator, an adjustable amplitude attenuator and a voltage-to-current converter.

Abstract: A phase-selective amplifier includes a first mixer with amplification switches to switch the amplification of the first mixer to n/2 conditions having approximately a sinusoidal relation. A second mixer receives the output of the first mixer, and an amplification switch is provided to switch the amplification of the mixer between a positive and a negative value. A voltage-controlled oscillator is provided with a phase control circuit, and logic elements are provided to connect the amplification switches to the phase control circuit.

Abstract: An improved signal transmission apparatus of two-wire type is disclosed.

Abstract: To permit a portable light meter to operate without zero adjustment and without excessive battery drain, a chopper-stabilized amplifier amplifies the DC signal from the light sensor of the light meter. The chopper in the chopper-stabilized amplifier is an FET circuit having a high impedance compensating circuit to avoid battery drain while compensating for interelectrode capacitance. The power supply obtains the ground level potential from the output of an operational amplifier with negative and positive potentials being generated from that reference potential so as to not require a center tap on the battery pack.

Abstract: In a demodulator circuit for a chopper amplifier including a rectifier and a smoothing filter having a capacitor, an impedance conversion circuit is connected to the output side terminal of the capacitor to ensure holding of the stored charges of the capacitor at each negative half-cycle of the amplitude-modulated AC signal applied to the demodulator circuit. A discharge circuit including a switching element is further provided for the capacitor and the discharge circuit is rendered conductive at each positive half-cycle of the amplitude-modulated AC signal which is also applied to a control terminal of the switching element.

Abstract: The invention relates to a method and apparatus for measuring the corrosion current of an elongated structure immersed in a fluid and provided with a cathodic protection device, the apparatus comprising at least one closed magnetic circuit immersed in the fluid and orientated so that a certain amount of electric current can pass therethrough, a coil on this magnetic circuit, measuring means connected to the terminals of this coil and modulation means (perforated rotating disc) for periodically varying, in time, the quantity of electric current circulating through the magnetic circuit. The invention is applied more particularly to the surveillance of underwater pipe-lines.

Abstract: A method and apparatus for determining boiler water conductivity to minimize erratic readings due to the random presence of steam in the region of the conductivity sensor. The apparatus includes circuitry for providing a signal responsive to the peak conductivity detected by the sensor. This peak signal is stored in a storage circuit having a relatively slow decay rate so as to not be disturbed by subsequent lower and erratic conductivity probe signals, with the stored peak signals being updated by subsequent peak readings more indicative of the true conductivity of the water. An embodiment which steps to subsequent peak readings is also disclosed.

Abstract: In an electrochemical cell passing a constant current, an electrode rotating asymmetrically with respect to a fixed electrode produces an ac voltage, having a component at the rotational frequency, between the rotating and fixed electrodes because the interelectrode distance and dc solution resistance between the electrodes vary. When this electrode is used in an operating two electrode cell, e.g., a plating bath, the ac voltage may be used to map the spatial current distribution. Measurements of solution conductivity may also be made.

Abstract: A device is provided for detecting the current level of a DC signal. It includes an even harmonic modulator to which a reference AC signal is applied. The unknown DC signal acts on the reference AC signal so that the output of the modulator includes an even harmonic whose amplitude is proportional to the unknown DC current.

Abstract: A method and device is disclosed whereby the number of revolutions of an axle or the angle of rotation of an axle are represented by a particular value. The value is preferably in the form of an electric analog signal. A pickoff element having a linearly-shaped primary coil and a linearly-shaped secondary coil is disposed so that the primary and secondary coils are in parallel with an air gap therebetween. The air gap is for the formation of a homogeneous stray field. A metallic disc which has a rim in the form of an Archimedes' spiral, is affixed to an axle. The disc is disposed in the air gap between the primary and secondary coils. A high frequency signal is supplied to the primary coil. Accordingly, when the axis is rotated, an amplitude modulated signal is developed at the secondary coil. The amplitude modulated signal is then demodulated and subsequently differentiated to provide an analog signal proportional to the angular rotation of the axle or the number of revolutions of the axle.

Abstract: A floating measurement amplifier comprising an emitter and a receiver ferromagnetically coupled but totally separated from each other galvanically, the emitter comprising a modulator feeding the primary winding of a signal transformer and a feed device feeding the primary winding of a feed transformer, and the receiver comprising a demodulator, identical to the modulator controlling the feed of the secondary winding of the signal transformer and an oscillator connected to the secondary winding of the feed transformer, said modulator and demodulator being formed of transistors controlled by their bases, the modulator being connected to the primary winding of the signal transformer and, through a capacitor, to the primary winding of the feed transformer, and the demodulator being connected to the secondary winding of the signal transformer and, through a capacitor, to the secondary winding of said feed transformer.