A signal processing method and a material testing machine are provided. A reference function processing part includes a data interval generation part for cutting out input signal from a load cell into time-domain data interval by cutting out the input signal of a predetermined time length, a reference function determining part for determining a reference function to be used in a transform process, and a transform part for transforming the interval data using the reference function. Considering the approximately straight lines near the two ends of the data interval, the reference function is a third degree polynomial function with tangents overlapping with the approximately straight line at both ends of the data interval.

A signal processing method and a material testing machine are provided. A reference function processing part includes a data interval generation part for cutting out input signal from a load cell into time-domain data interval by cutting out the input signal of a predetermined time length, a reference function determining part for determining a reference function to be used in a transform process, and a transform part for transforming the interval data using the reference function. Considering the approximately straight lines near the two ends of the data interval, the reference function is a third degree polynomial function with tangents overlapping with the approximately straight line at both ends of the data interval.

A method for detecting low-frequency oscillations, in particular subsynchronous resonances, in an electrical supply grid is provided. The grid has a line voltage with a rated line frequency. The method comprises recording first and second series of measurements each for performing a frequency analysis (FFT). The method includes performing a lower frequency analysis for the first series for a lower frequency range and forming a lower amplitude spectrum. The method includes performing an upper frequency analysis for the second series for an upper frequency range and forming an upper amplitude spectrum. The method includes testing whether a low-frequency oscillation component can be identified in the lower amplitude spectrum, and testing whether a low-frequency oscillation component can be identified in the upper amplitude spectrum, where the presence of a low-frequency oscillation is assumed when a low-frequency oscillation component is identified in at least one of the lower and upper amplitude spectra.

A method for detecting low-frequency oscillations, in particular subsynchronous resonances, in an electrical supply grid is provided. The grid has a line voltage with a rated line frequency. The method comprises recording first and second series of measurements each for performing a frequency analysis (FFT). The method includes performing a lower frequency analysis for the first series for a lower frequency range and forming a lower amplitude spectrum. The method includes performing an upper frequency analysis for the second series for an upper frequency range and forming an upper amplitude spectrum. The method includes testing whether a low-frequency oscillation component can be identified in the lower amplitude spectrum, and testing whether a low-frequency oscillation component can be identified in the upper amplitude spectrum, where the presence of a low-frequency oscillation is assumed when a low-frequency oscillation component is identified in at least one of the lower and upper amplitude spectra.

A method evaluates a frequency spectrum representative of at least one time-dependent signal, the at least one time dependent signal being derived from an output from a measuring device under predetermined measuring device operating conditions. The time-dependent signal, includes a portion being representative of a wanted signal, and a portion being representative of noise. The method includes the steps of determining, based on the frequency spectrum of the signal, a value representative of the noise floor, identifying, based on the frequency spectrum of the signal derived under the predetermined operating condition, a peak component, and if the peak component satisfies a relative peak criterion determined on the basis of the determined value representative of the noise floor, determining the wanted signal by applying a predetermined algorithm. The invention further relates to a method for determining flow of a vortex measuring device, and a vortex sensor.

Provided is a method for detecting low-frequency oscillations, in particular subsynchronous resonance, in an electrical supply grid, wherein the electrical supply grid has a grid voltage at a grid nominal frequency, comprising the steps of capturing at least one electrical signal from the electrical supply grid, and evaluating the electrical signal by means of wavelet analysis, during which a time-dependent frequency pattern is created by analyzing a correlation of the captured signal with a predetermined wavelet mother function, wherein the presence of a low-frequency oscillation is assumed if at least one further low-frequency frequency component is present in the time-dependent frequency pattern in addition to a fundamental component.

A peak frequency detection device provided with: an n multiplication unit that multiplies each element of a digital data string by n (n is an integer of 2 or more); an FFT unit that derives, as a virtual peak frequency, a frequency that corresponds to the maximum value of a power spectrum that is obtained by performing a fast Fourier transform of a digital data string of N (N is an integer of a power of 2 and is determined in accordance with a sampling frequency (f.sub.s), a sampling resolution (f.sub.tg), and a time window length (T.sub.tg)) sample frequencies (f.sub.s) that are multiplied by n; and a 1/n multiplication unit that outputs the value of the virtual peak frequency multiplied by 1/n as the peak frequency of the digital data string. The peak frequency detection device satisfies n1/(f.sub.tgT.sub.tg), f.sub.s/(nf.sub.tg)Nf.sub.sT.sub.tg, and f.sub.s>2nf.sub.ch.

A peak frequency detection device provided with: an n multiplication unit that multiplies each element of a digital data string by n (n is an integer of 2 or more); an FFT unit that derives, as a virtual peak frequency, a frequency that corresponds to the maximum value of a power spectrum that is obtained by performing a fast Fourier transform of a digital data string of N (N is an integer of a power of 2 and is determined in accordance with a sampling frequency (f.sub.s), a sampling resolution (f.sub.tg), and a time window length (T.sub.tg)) sample frequencies (f.sub.s) that are multiplied by n; and a 1/n multiplication unit that outputs the value of the virtual peak frequency multiplied by 1/n as the peak frequency of the digital data string. The peak frequency detection device satisfies n1/(f.sub.tgT.sub.tg), f.sub.s/(nf.sub.tg)Nf.sub.sT.sub.tg, and f.sub.s>2nf.sub.ch.