Abstract: A harmonic injection point a is set on a power line extending downstream from a harmonic measuring point b in an electric power system. The currents of interharmonics are injected to the harmonic injection point a by a current injection device. The frequencies of the interharmonics are located on both sides of the frequency of an n-th targeted harmonic in frequency spectrum and each of the frequencies is a nonintegral multiple of the frequency of a fundamental wave of an electric power transmitted by the electric power system. The current values and voltage values of the interharmonics at the harmonic measuring point are detected to thereby obtain admittance values of an equivalent circuit of a power line extending upstream from the harmonic measuring point b when the interharmonics flow therethrough. An admittance value of the equivalent circuit of the power line when the targeted harmonic flows therethrough is determined by interpolating the admittance values for the interharmonics.

Abstract: An active filter device provided for compensating harmonic distortion in a supply line by injecting for each harmonic (fk) to be considered a compensation current. The compensation current being determined by injecting a monitoring current on the supply line at a first (f1) and second (f2) frequency value, offset respectively on either side of the considered harmonic, and measuring response currents generated by the supply line upon injection of said monitoring currents.

Abstract: A method for determining the harmonic response of a device under test (DUT) to the input fundamental frequency component of an input signal is performed on a vector network analyzer. A first response of the DUT at the harmonic frequency is obtained by measuring the linear response of the device at the harmonic frequency of interest after appropriate normalization. A second response of the DUT is obtained by measuring the response of the DUT at the harmonic frequency to an input which comprises a source input fundamental with its harmonic components after appropriate normalization. The harmonic response of the DUT to the source input fundamental alone is computed from the first and second responses. Such computations allow the harmonic response of the DUT to be measured free of stimulus source harmonics, so that overall harmonic measurement accuracy and dynamic range is enhanced.

Abstract: A method for determining the harmonic phase response ∠POx of a device under test (DUT) is performed on a vector network analyzer (VNA). The phase ∠GN1 of the transfer response GN1 of the DUT at the fundamental frequency is determined from VNA measurements after appropriate normalization. The corrected phase ∠GHxC of the harmonic transfer response of the DUT is determined from VNA measurements after appropriate normalization. The corrected phase ∠GHxC of the harmonic transfer coefficient GHx is subtracted from a predetermined phase reference ∠refx to obtain a difference ∠refx−∠GHxC, and the phase ∠GN1 of the transfer coefficient GN1 at the fundamental frequency is added to the difference ∠refx−∠GHxC to obtain the harmonic phase offset ∠POx. For the second and third harmonics using a clipping waveform, the phase reference ∠refx is 180°.

Abstract: Apparatus and method to detect corrosion in metal junctions. Corroded metal junctions are usually discovered by visual inspection. The present invention detects corrosion in metal junctions when it is not visually apparent. A corroded metal junction acts as a nonlinear device. It generates harmonics and other nonlinear products (such as intermodulation) of any signals applied to the junction. The presence of relatively high level harmonics and/or intermodulation products indicates directly that corrosion has occurred. To detect corrosion in a metal junction, one couples a fundamental frequency signal (f0) into the junction and tests for harmonics of that frequency, especially the third harmonic. Harmonic frequency signals that are relatively large (i.e., above the harmonics generated by the testing system) indicate the presence of corrosion. Measurements to determine if a metal junction is corroded are performed without disturbing the junction.

Abstract: An electromagnetic field generator is provided which consists of a regulated self contained voltage supply connected to a high frequency clock which drives one or more printed circuit board antennas. The clock may be a TTL or ECL based clock for example. The electromagnetic field generator is used in a method of testing the shielding effectiveness of an enclosure. Two measurements are made with a measurement antenna of emissions from the electromagnetic field generator, one with the enclosure in place and another without the enclosure in place, the shielding effectiveness being the difference between these two measurements.

Abstract: A device for detecting harmonics in a current carrying conductor, comprises current probe for placing adjacent a current carrying conductor, the current probe generating an output signal in response to the current in the conductor; a circuit operably connected to the current probe for processing the output signal from the current probe; the circuit including a switching portion responsive to the output of the current probe for automatically turning on or off the circuit when the current probe senses current in the electrical conductor; and a display for the output of the circuit for indicating the presence of harmonics in the conductor. The display includes a plurality of various colored LEDs that are lit depending on the severity of the harmonics of interest that are detected. The circuit also includes a microcontroller for computing the Fourier coefficients of the harmonics of interest and an automatic gain control feature for auto-ranging for various current inputs from the current probe.

Abstract: A method and apparatus provides a technique for measuring characteristics of a harmonic pollution source connected to an alternating current power distribution system. The apparatus has a harmonic current meter and a harmonic voltage meter. Also, the apparatus has a harmonic perturbation device which can produce changes in the harmonic energy present in the power distribution system. The perturbation device can be a harmonic shunt or a harmonic frequency generator. In operation, harmonic voltage and current measurements are made at the connection point between the harmonic pollution source and the rest of the power distribution system. One set of voltage and current measurements is made with the harmonic perturbation device connected and one set of measurements is made with the harmonic perturbation device disconnected. The measurements are performed at the frequencies of interest.

Abstract: Frequencies fx between the measurement harmonic (mth-degree harmonic) and the (m±1)th-degree harmonics are determined from an expression of fx=(fs*m)±{(fs/n)*k)} where n and k are each an integer. Currents of inter-harmonics of the frequencies fx above and below the measurement harmonic are injected into an inject point in a power system in n cycles of the fundamental wave. Voltage at the inject point based on the injected currents and currents at least either upstream or downstream from the inject point are measured. Admittances for the inter-harmonics above and below the measurement harmonic on at least either the upstream or downstream side from the harmonic inject point are calculated from the measurement results. Interpolation processing based on the calculation results is performed, thereby finding and determining an admittance for the measurement harmonic.

Abstract: A method of determining parameters of a harmonic pollution source connected to a power line at a connection point. The harmonic pollution source is a power customer and the power is supplied by an electric utility. The electric utility is also a source of harmonic pollution. Both the utility and customer can be modeled as a harmonic current source in parallel with an impedance. In the method of the present invention, a harmonic voltage and a harmonic current are measured at the connection point between the utility and customer. The voltage and current measurements are combined with the known reference impedances in a calculation to yield the magnitude of current produced by the customer or utility harmonic current sources. Also, the present invention provides a method for determining the relative harmonic pollution contributions from the utility and customer. Both the utility and customer can then know exactly how much harmonic pollution they are emitting into the power line to which they are connected.

Abstract: The present invention entails a circuit and method for determining the distortion created by a transformer used in data communications. The circuit according to the present invention comprises a transmitting circuit, a back matching circuit, and a subtracting circuit. The transmitting circuit generates a test signal to be transmitted into a transformer, the transmitting circuit having a transmitting output for coupling to a transformer. Once applied to the transformer, the test signal is distorted by the transformer, where the transformer creates harmonics of the test signal and other signal distortion. The back matching circuit generates a scaled test signal that is subtracted from the distorted test signal in the subtraction circuit. The result is a diminished peak at the test signal in comparison to the harmonics such that the distortion by the transformer can be determined using a measuring device with a relatively low dynamic range.

Abstract: Single-phase currents at two frequencies f.alpha. and f.beta. (f.alpha.<n.multidot.fs<f.beta.) of non-integral multiples of a system fundamental wave frequency fs sandwiching an targeted harmonic (frequency n.multidot.fs) are injected between two phases of a three-phase power system as interharmonic currents. A frequency analysis of measurement current and measurement voltage of each phase in the system is carried out and a positive-phase-sequence current I1, a positive-phase-sequence voltage V1, a negative-phase-sequence current I2, and a negative-phase-sequence voltage V2 are detected for each of the two frequencies f.alpha. and f.beta. in the system based on injecting of the interharmonic currents. Positive-phase-sequence and negative-phase-sequence admittances Y1 and Y2 or positive-phase-sequence and negative-phase-sequence impedances Z1 and Z2 are found for each of the frequencies f.alpha. and f.beta. in the system as Y1=I1/V1 and Y2=I2/V2 or Z1=V1/I1 and Z2=V2/I2.

Abstract: A non-contact probe provides information as to relative amplitudes of harmonics of a current or voltage waveform as well as total harmonic distortion. The probe includes a non-contact sensor with an amplifier coupled thereto. Output signals from the amplifier are digitized and analyzed in a programmed processor. Output from the processor provides a display of relative harmonic amplitudes as well as an indicator of total harmonic distortion.

Abstract: A harmonics survey system includes an induction coil arranged so as to cross over a magnetic flux generated by a current passing a distribution line to be surveyed and adapted to detect a detection current caused by an electro motive force in proportion to the current passing the distribution line, a harmonics detection unit operatively connected to the induction coil and adapted to detect a fundamental component and a harmonic component of the detection current detected by the induction coil, a harmonic current content operation unit for operating the harmonic current content of the harmonic component with respect to the fundamental component detected by the harmonic detection unit, and an indication unit for indicating the harmonic current content operated by the harmonic current operation unit.

Abstract: A non-contact probe provides information as to relative amplitudes of harmonics of a current or voltage waveform as well as total harmonic distortion. The probe includes a non-contact sensor with an amplifier coupled thereto. Output signals from the amplifier are digitized and analyzed in a programmed processor. Output from the processor provides a display of relative harmonic amplitudes as well as an indicator of total harmonic distortion.

Abstract: An outgoing harmonic level evaluator which evaluates the amount of outgoing harmonics by computing correction to the amount of harmonics measured at a receiving point without the need for summing the measurement values of generated harmonics in load bus lines.

Abstract: A circuit to discriminate the source of harmonic distortion of the output voltage comprises voltage sensors coupled to the output terminals of a source of electric power and to a point of regulation remote from the source for sensing the output voltage waveform present at each of these locations. The circuit then utilizes these two sensed waveforms to discriminate the source of any harmonic distortion between the source of electric power and the utlization equipment. This circuit calculates the percentage total harmonic content of each of the sensed waveforms, and compares them to determine the source of distortion. If the percentage total harmonic content sensed at the point of regulation is greater than that sensed at the terminals of the source of electric power, the source of distortion is discriminated to be the utilization equipment; otherwise, the source of distortion is identified to be the source of electric power.

Abstract: Analog and mixed signal integrated circuits are tested using the modified Volterra series to model the integrated circuit being tested. An adaptive algorithm, for example, least mean square or Kalman, is used to determine to coefficients of the Volterra series. The coefficients are then used to calculate the THD and SNR.

Abstract: A system (36, 98) for determining the linearity of an RF detector (46, 106). A first technique involves combining two RF signals from two stable local oscillators (38, 40) to form a modulated RF signal having a beat frequency, and applying the modulated RF signal to a detector (46) being tested. The output of the detector (46) is applied to a low frequency spectrum analyzer (48) such that a relationship between the power levels of the first and second harmonics generated by the detector (46) of the beat frequency of the modulated RF signal are measured by the spectrum analyzer (48) to determine the linearity of the detector (46). In a second technique, an RF signal from a local oscillator (100) is applied to a detector (106) being tested through a first attenuator (102) and a second attenuator (104).

Abstract: The present invention relates to a system and method for determining the effects of linear and nonlinear loads on electrical power systems. The invention utilizes stored load characteristic data in terms of current spectra at predefined voltage values and network impedances to determine the voltage drop between an electrical substation bus and an electrical load bus. The actual load voltage is determined by an iteration technique which takes the difference between a collected substation voltage and the voltage drop and compares the result of the difference to an estimated load voltage. For each iteration the estimated load voltage is re-estimated until the difference result equals the estimated voltage, thereby determining the actual load voltage. Knowing the actual load voltage, permits determination of actual current and power values which are compared to collected substation current and power values. If the values are equal, the effects of the harmonics are known.

Abstract: An apparatus and method to identify a harmonic producing load on a utility electrical network is described. The apparatus is connected to the utility electrical network at a location adjacent to a load. The apparatus includes a network voltage node to receive a voltage signal, and a network current node to receive a current signal. The apparatus also includes harmonic filters to process the voltage signal and current signal to isolate selected harmonic voltage signals and selected harmonic current signals. A signal processor derives a set of selected power signals from the selected harmonic voltage signals and the selected harmonic current signals. The signal processor also identifies any positive polarity signals in the set of selected power signals. In response to a positive polarity signal, the signal processor activates a sensory output device to indicate that harmonics are being produced by the load.

Abstract: A microprocessor based device for generating a representation of the total harmonic distortion in an ac waveform derives from digital samples of the waveform a fundamental signal representing the value of the fundamental frequency component of each sample. A harmonic signal is then generated as the difference between the sample value and the fundamental component of the sample. An output signal representing total harmonic distortion is then generated as the ratio of the RMS value of the harmonic signal to the RMS value of the fundamental signal converted to a percentage.

Abstract: A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.

Abstract: An integral electronic meter system diagnostics package including a microprocessor, storage memory, logic for automatically and periodically performing a pre-select series of system diagnostic tests, and recording any results which exceed predefined programmable thresholds, and display means for displaying error and/or diagnostic messages identifying selected diagnostic data and/or errors discovered in the meter tests during a predefined period.

Abstract: A method and apparatus for fast response and distortion measurement of a signal transfer device. A computer processor generates a multitone test signal of predetermined duration and stores it in a memory. The test signal is read out, converted to analog form, if necessary, and applied to the input of a device under test. The output produced by the device under test in response to the test signal is acquired and digitized, if necessary, and a Fast Fourier Transform is performed on the acquired data to determine its spectral characteristics. Frequency response, harmonic distortion, intermodulation distortion, phase distortion, wow and flutter and other signal transfer characteristics are measured by the CPU by analysis of the output signal.

Abstract: An apparatus for the analysis of power quality and the effects of harmonic distortions on machinery or equipment. The apparatus is compact, portable, and non-invasive in that the apparatus can be operatively connected to an electrical carrier without power interruption. A display device is built in allowing graphical display of averaged or continuously updated measurements and analysis. A central processing unit analyzes measurements using Fourier analysis.

Abstract: Electrical signals suffer usually from distortion and noise. This invention gives a very precise and simple digital circuitry as well as basis for software to measure the phase difference between harmonic components of any of two of the input signals. The apparatus may be used also for measuring the voltage, current, impedance, apparent power, active power, reactive power, total harmonic distortion or distortion of preselected harmonics in any two of a plurality of test signals, autocorrelations and cross-correlations for any subset of the input signals. The apparatus may also be used to analyze the amplitude of harmonic components, to filter DC or specific harmonic components of any of the result in an analog or digitized waveform, and to measure object distance for radar, sonar, and telecommunication applications. The apparatus design is based on modern digital signal processor chips and multi-processors operation.

Abstract: A portable instrument for locating and measuring harmonic distortion in a conductor. The instrument permits voltage and current harmonics to be easily read while the load is changing. Thus, the instrument may provide a great deal of insight as to the source of problem causing harmonics.

Abstract: The present invention relates to a method of calibrating levels of a waveform analyzing apparatus. An analog switch produces a square wave signal of a low frequency by switching ON and OFF a preset level of DC voltage from a DC voltage setting circuit at a frequency of a control signal from a frequency setting circuit. The square wave signal is applied to the waveform analyzing apparatus and the low frequency output level is calibrated by a theoretical level of a frequency spectrum of the square wave signal. A diode detecting circuit is calibrated at the low frequency using the calibrated waveform analyzing apparatus, which in turn is calibrated at a high frequency using the calibrated diode detecting circuit.

Abstract: Waveform data read out of a memory is converted by a D/A converter into an analog waveform, and amplified by an amplifier to generate a waveform signal. To cancel a distortion generated in the amplifier, a composite waveform composed of a distortion canceling signal waveform and a fundamental frequency signal waveform to be generated is written into the memory. To determine a distortion canceling signal, the fundamental frequency component in the signal waveform is attenuated by a notch filter. The signal waveform is then converted by an A/D converter into a digital multi-sine waveform. This waveform is input to a computation and control part and subjected to a Fourier transform analysis to compute the amplitude and phase of each harmonic component. Further, the output of the amplifier the memory, is fed via the notch filter and the A/D is input to the computation and control part, where it is subjected to a Fourier transform analysis to compute the amplitude and phase of each distortion component.

Abstract: A vector network analyzer for performing swept frequency measurements on non-linear RF devices, using either an internal or external signal source. This simplifies and speeds linear and non-linear amplifier and mixer measurements, such as impedance, amplifier gain, and mixer conversion loss, on the one hand, and measurement of harmonics, on the other hand.

Abstract: A method and apparatus for determining the total harmonic distortion and the power factor of a non-linear load circuit coupled to an a.c. power source generating a.c. current and a.c. voltage, the a.c. current input to the load circuit being in phase with the a.c. voltage provided across the load circuit by the a.c. power source. The invention measures the total harmonic distortion of a.c. current and a.c. voltage at the non-linear load circuit and calculates the total harmonic distortion and the power factor as a function of both.

Abstract: A method and apparatus for monitoring the degradation of elastomeric materials is provided. Piezoelectric oscillators are placed in contact with the elastomeric material so that a forced harmonic oscillator with damping is formed. The piezoelectric material is connected to an oscillator circuit,. A parameter such as the resonant frequency, amplitude or Q value of the oscillating system is related to the elasticity of the elastomeric material. Degradation of the elastomeric material causes changes in its elasticity which, in turn, causes the resonant frequency, amplitude or Q of the oscillator to change. These changes are monitored with a peak height monitor, frequency counter, Q-meter, spectrum analyzer, or other measurement circuit. Elasticity of elastomers can be monitored in situ, using miniaturized sensors.