594 results about "Measurement frequency" patented technology

A fault is located in a power distribution system having a line frequency. The power distribution system includes a plurality of phases, at least one feeder, and each feeder includes at least one segment. The fault is located by detecting a faulted phase from the plurality of phases of the power distribution system. A measurement signal having a measurement frequency is injected into the detected faulted phase, the measurement frequency being a different frequency than the line frequency. The fault location is determined for a selected segment based on at least one measured residual current corresponding to the injected signal and a predetermined relative impedance of the power distribution system.

The invention provides a method and system for collecting aggregate information about network traffic, while maintaining processor load relatively constant despite substantial variation in network traffic, and capable of substantially accurate frequency measurement even for relatively infrequent events. A packet monitoring system includes an input port for receiving network packets, a sampling element for selecting a fraction of those packets for review, and a queue of selected packets. The packets in the queue are coupled to a packet-type detector for detecting packets of a selected type; the system applies a measurement technique for determining a frequency measure for those detected packets. The system includes a feedback technique for adaptively altering the sampling rate fraction, responsive to the queue length and possibly other factors, such as processor load or the detected frequency measure. The measurement technique also determines an error range and a measure of confidence that the actual frequency is within the error range of the measured frequency. The system can detect packets of multiple selected types essentially simultaneously, and provide measured frequencies and error ranges for all of the multiple selected types at once. Also, the measurement technique is selected so as to impose relatively light processor load per packet.

The invention provides a frequency measurement method based on an FPGA. A standard reference clock is adopted to count the number of pulses of a measured signal in a unit time (1s) and the number of the pulses of the measured signal in the unit time (1s) is the frequency of the signal. Due to the fact that the starting moment of a gate and the finishing moment of the gate are random for the signal, a pulse period quantization error can be produced, and measurement accuracy needs to be analyzed further: the pulse period of a signal to be measured is set to be Tx, the frequency is set to be Fx, and when the measuring time T equals to 1s, the measurement accuracy & meets the equation that &=Tx/T=1/Fx. The fact that measurement accuracy in a direct frequency measurement method is relevant to the frequency of the signal is known, the higher the frequency of the signal to be measured is, the higher the measurement accuracy is, and otherwise, the lower the frequency of the signal to be measured is, the lower the measurement accuracy is. The direct frequency measurement method is only suitable for measurement of the signal at the higher frequency and can not meet the demand that the measurement accuracy remains unchanged in the whole measurement frequency band. In order to overcome the defect of inaccuracy in low-frequency-band measurement, gating signals and the measured signal are used for carrying out dual control on enable signals of the counter, and therefore accuracy is improved.

The invention discloses a broadband tunable single-passband microwave photon filter generating system. The system comprises a laser, an optical coupler, a polarization modulator, a dispersion displacement optical fiber, a photoelectric detector, a vector network analyzer, a strength modulator and an optical fiber; the laser is used for providing continuous light signals; the optical coupler is used for dividing the continuous light signals into the first path of light signals and the second path of light signals; the polarization modulator is used for modulating the polarization state of the first path of light signals; the dispersion displacement light fiber is used for performing stimulated Brillouin scattering on the detection light signals under the induction effect of pump light signals; the photoelectric detector is used for receiving the detection light signals which are processed in a stimulated Brillouin scattering mode and output by the dispersion displacement optical fiber and generating microwave signals; the vector network analyzer is used for receiving microwave signals output by the photoelectric detector, performing measurement frequency response on the microwave signals, and outputting the microwave signals to the a first polarization modulator at the same time; the strength modulator is used for modulating the polarization state of the first path of light signals and outputting the first path of light signals which are modulated; the optical fiber is used for filtering the first path of light signals which are modulated, and the first path of light signals serve as the pump light signals.

In one embodiment, an acoustic distance measurement system can dynamically adjust its measurement frequency to a frequency that is within a preselected bandwidth of the resonant frequency of an acoustic transducer used in making acoustic distance measurements.

This invention discloses one method and device to improve time zone signals frequency stability measurement, which comprises the following steps: reference time signals are processed through DDS technique to get stable and accurate circle signals; expending measurement frequency signals range to get better reference signals and signals to be tested at fine time measurement; using DDS unit to process measurement frequency signals; when circle sample time singles come, according to fine time measurement module minimum resolution rate to test signals to be tested with reference time signals minimum phase difference to make the meter work to fulfill frequency signal measurement.

The invention provides a method for measuring a sine signal with high accuracy, which is realized by steps of data acquisition system sampling, discrete Fourier transform, peak searching, frequency measurement, and amplitude and phase measurement. The invention provides an interpolating method capable of correcting leakage effect in a long-range and a short-range simultaneously to realize high accuracy measurement on parameters of the sine signal by the Fourier transform algorithm. The method can improve the accuracy for measuring the sine signal to over 10.

The present invention relates to the technical field of radars and discloses a laser radar system based on MEMS micro mirror scanning. The laser scanning of a target area is carried out by using the outgoing laser emitted by an MEMS micro mirror reflection laser according to a preset specified rotation angle, a receiving detector receives the reflection laser of a target reflection object in a target area and converts the reflection laser into an echo pulse signal, and a signal processing module receives and processes the echo pulse signal so as to obtain the position information of the target reflection object. Therefore, the laser radar system has a high measurement frequency and low cost.

Real time battery impedance spectrum is acquired using one time record, Compensated Synchronous Detection (CSD). This parallel method enables battery diagnostics. The excitation current to a test battery is a sum of equal amplitude sin waves of a few frequencies spread over range of interest. The time profile of this signal has duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known, synchronous detection processes the time record and each component, both magnitude and phase, is obtained. For compensation, the components, except the one of interest, are reassembled in the time domain. The resulting signal is subtracted from the original signal and the component of interest is synchronously detected. This process is repeated for each component.

Methods of rapidly measuring the impedance spectrum of an energy storage device in-situ over a limited number of logarithmically distributed frequencies are described. An energy storage device is excited with a known input signal, and the response is measured to ascertain the impedance spectrum. The excitation signal is a limited time duration sum-of-sines consisting of a select number of frequencies. In one embodiment, magnitude and phase of each of frequency of interest within the sum-of-sines is identified when the selected frequencies and sample rate are logarithmic integer steps greater than two. This technique requires a measurement with a duration of one period of the lowest frequency. In another embodiment, where the selected frequencies are distributed in octave steps, the impedance spectrum can be determined using a captured time record that is reduced to a half-period of the lowest frequency.

Real-time battery impedance spectrum is acquired using a one-time record. Fast Summation Transformation (FST) is a parallel method of acquiring a real-time battery impedance spectrum using a one-time record that enables battery diagnostics. An excitation current to a battery is a sum of equal amplitude sine waves of frequencies that are octave harmonics spread over a range of interest. A sample frequency is also octave and harmonically related to all frequencies in the sum. The time profile of this signal has a duration that is a few periods of the lowest frequency. The voltage response of the battery, average deleted, is the impedance of the battery in the time domain. Since the excitation frequencies are known and octave and harmonically related, a simple algorithm, FST, processes the time record by rectifying relative to the sine and cosine of each frequency. Another algorithm yields real and imaginary components for each frequency.

A method and apparatus for measuring changes induced in an inductive field on a wire-loop of an oscillator circuit based upon variations in a current function without the need to measure frequency changes. Induced noise has independent effects upon the current function and voltage function of an inductance measurement circuit. By inductively coupling one input and directly coupling the second input of a comparator circuit to the inductance measurement circuit, the phase of the current function can be adjusted to coincide with the phase of the voltage function. By combining the voltage function with the current function, an output isolating the induced noise from the measured inductance is obtained.

Apparatus and methods for adaptively, reliably, and accurately measuring the frequency of an alerting or other signaling tone. A tone detector measures the frequency of a tone (continuous or pulsed) with a high degree of accuracy (e.g., to within 1 part in 10,000). Two lower order or smaller DFTs measure the energy level in two separate but intersecting frequency ranges. A simple ratio is determined from the relative energy measured from discrete Fourier transforms relating to each of the two separate frequency ranges, and an actual measured frequency is determined.

The invention relates to a method for assessing an insulation state of oil paper based on characteristic quantity of frequency domain dielectric spectroscopy. The method comprises following steps: utilizing a linear medium response equivalent circuit to simulate polarization characteristics of the insulation state of oil paper for a transformer and setting up the relationship between linear medium response equivalent circuit parameters, frequency-domain characterization complex capacitance and dielectric loss factors; then, utilizing complex capacitances with high frequency bands and a parametric equivalent circuit model for dielectric loss characteristic quantity and finally, integrating dielectric loss curves with low frequency bands at prediction sections, wherein the range of frequency bands in a dielectric loss frequency domain is equally divided into n frequency points (n larger than or equal to 1), n frequency points correspond to n dielectric loss integral value and n frequencies and corresponding dielectric loss integral value are fitted to a function curve. The method for assessing an insulation state of oil paper based on characteristic quantity of frequency domain dielectric spectroscopy has following beneficial effects: in order to obtain much more insulation information carried by dielectric loss factors within the limited measurement frequency domain, integrals of dielectric loss factors are utilized in the predicted low-frequency section as characteristic parameters for assessment of insulation state; and dielectric loss integral value within the low-frequency stage obtained by calculations is utilized for determining the insulation aging state of oil paper.

A method for measuring a compact range antenna by three reflectors comprises the following steps of: determining a system mapping function according to the distribution of a feed source field and the distribution of a system outlet field; tracking and analyzing the electromagnetic wave emitted by the feed source by adopting a dynamic waveband tracking theory; and determining all mirror surface parameters of a first forming auxiliary reflector and a second forming auxiliary reflector by the system mapping function, the feed source field wavefront parameters and the main reflector surface parameters. The embodiment of the invention also discloses a system for measuring compact range antenna by three reflectors. The system and the method can be applicable to the feed source higher than 300GHz, and lead the system outlet field to have large quiet zone utilization coefficient (achieving more than 70%), high cross polarization isolation degree, compact structure and wide measurement frequency bands.

The invention discloses a high-frequency vibration measurement distributed fiber sensing system based on a frequency division multiplexing technology. A phase-sensitive optical time domain reflection system and a Mach-Zehnder interferometer are combined together, positioning is performed by use of a phase-sensitive optical time domain reflection technology, high-frequency vibration measurement is realized by use of the Mach-Zehnder interferometer, a vibration position corresponds to a vibration frequency by use of a spectrum mapping method, and thus the high-frequency vibration measurement distributed fiber sensing system based on the frequency division multiplexing technology is formed. The system has the following advantages: longer-distance sensing is realized; the problem that a system positioning signal-to-noise ratio is affected by frequency measurement sensitivity is solved based on a simple sequential control and modulation method; frequency blind areas of the system, exiting in a measurement frequency band are removed; positioning and frequency measurement of high-frequency multipoint vibration are realized; the apparatus provided by the invention works stably and can accurately measure the position and the frequency of vibration in multiple measurement; and accurate positioning and frequency measurement of multipoint high-frequency vibration can be realized under the condition of a low cost.

The invention provides a microwave anechoic chamber performance measuring method, which comprises the following steps of: adopting a microwave anechoic chamber performance measuring system, and setting a dead zone parameter, a measuring frequency, a signal source power, a scanning trace and a kinematic velocity of a receiving antenna, and a rotation direction and a rotation velocity of a transceiving antenna according to the requirements of a microwave anechoic chamber performance analysis test; driving a signal source according to the signal source power; driving each stepping motor to control each moving part to move according to the scanning trace and the kinematic velocity of the receiving antenna, and the rotation direction and the rotation velocity of the transceiving antenna; and controlling a signal receiver to receive a signal of the receiving antenna according to the measuring frequency, and storing the signal. The method can be adopted to be applied in a microwave anechoic chamber flexibly so as to measure along different scanning traces; and a computer is adopted to realize automatic measurement of microwave anechoic chamber dead zone reflectivity level, cross polarization character, multi-path loss uniformity, and field uniformity performance indexes, so that the measuring efficiency is improved.

The invention relates to a system for measuring half-wave voltage of a phase modulator and a measurement method. The measurement system comprises a laser generator, a polarization controller, a microwave signal generator, an optical interferometer, a power meter and a processor. The method comprises the following steps of: connecting a phase modulator to be measured into a detection system; determining working parameters of the system, and adjusting working conditions of the system; measuring optical power values under the condition of modulating microwave signals with different amplitudes, and comprehensively processing data; and measuring the half-wave voltage at different frequencies. By the system and the method, all the parameters measured at the same detection frequency are comprehensively processed by the characteristic of high resolution of modulation signals generated by the microwave signal generator to obtain a half-wave voltage value at the frequency, and the half-wave voltage value is circularly processed to obtain half-wave voltage values at various detection frequencies; and therefore, the system and the method have the characteristics that the system and the method are high in resolution of measurement frequency, the phase modulator has a plurality of measurement frequency points and a plurality of half-wave voltage measurement values and is high in accuracy, the using performance of a high-speed phase modulator can be exerted, the system and the method are systematical in measurement and low in measurement cost, and the like.

Electrochemical Impedance Spectrum (EIS) data are used directly to predict the pulse performance of an energy storage device. The impedance spectrum of the EIS is obtained in-situ using pre-existing techniques. A simulation waveform is configured such that the period of the pulse is greater than or equal to the lowest frequency of the impedance measurement. If the pulse is assumed to be periodic for analysis purposes, the complex Fourier series coefficients can be obtained. The number of harmonic constituents are selected so as to appropriately resolve the response, but the maximum frequency should be less than or equal to the highest frequency of the impedance measurement. In some cases, the measured frequencies of the impedance spectrum do not match the corresponding harmonic components of the simulated pulse wave. This is resolved by estimating the impedance measurements at the desired frequencies using linear interpolation, cubic spline fits, or other comparable methods. Using a current pulse as an example, the Fourier coefficients of the pulse are multiplied by the impedance spectrum at the corresponding frequency to obtain the Fourier coefficients of the voltage response to the desired pulse. The Fourier coefficients of the response are then summed reassemble to obtain the overall time domain estimate of the voltage using the Fourier series analysis. Thus, the response of an energy storage device to an anticipated or desired pulse can be estimated using low-level, charge neutral impedance measurements combined with Fourier series analysis.