A method includes a) counting whole periods of a signal during a first period of a reference signal, b) repeating step a) for each period of the reference signal until a first duration is equal to a first quantity of periods of the reference signal, and c) determining a first average of the whole periods. The method also includes repeating at least one of steps a) to c) and at each repetition shifting a start of the counting of step a) by at least one period of the reference signal, and in steps b) and c) accounting for whole periods of the signal already counted during the at least one preceding group of steps a) and b). The method includes determining a second average of the first averages, and determining the frequency of the signal from the second average and the frequency of the reference signal.

In an embodiment, a method for measuring an average frequency of an AC signal includes receiving the AC signal, triggering a first counter that is clocked at a first frequency, detecting each zero crossing of the AC signal in a predetermined crossing direction, recording a value of the first counter at each detected zero crossing, incrementing a second counter at each detected zero crossing, and calculating the average frequency of the AC signal based on the first frequency, a last recorded value of the first counter, and a last value of the second counter.

A method includes a) counting whole periods of a signal during a first period of a reference signal, b) repeating step a) for each period of the reference signal until a first duration is equal to a first quantity of periods of the reference signal, and c) determining a first average of the whole periods. The method also includes repeating at least one of steps a) to c) and at each repetition shifting a start of the counting of step a) by at least one period of the reference signal, and in steps b) and c) accounting for whole periods of the signal already counted during the at least one preceding group of steps a) and b). The method includes determining a second average of the first averages, and determining the frequency of the signal from the second average and the frequency of the reference signal.

A method includes a) counting whole periods of a signal during a first period of a reference signal, b) repeating step a) for each period of the reference signal until a first duration is equal to a first quantity of periods of the reference signal, and c) determining a first average of the whole periods. The method also includes repeating at least one of steps a) to c) and at each repetition shifting a start of the counting of step a) by at least one period of the reference signal, and in steps b) and c) accounting for whole periods of the signal already counted during the at least one preceding group of steps a) and b). The method includes determining a second average of the first averages, and determining the frequency of the signal from the second average and the frequency of the reference signal.

Provided a method comprising: obtaining waveform data sets of a periodic electric waveform signal, with a length set to one cycle time; calculating a frequency spectrum for each waveform data set; extracting and separating odd and even frequency harmonics to create odd and even frequency harmonic matrices on which a canonical correlation analysis (CCA) being applied to obtain CCA features; performing linear transformation on the CCA features to obtain linear transformed features; generating a model based on the linear transformed features; performing magnitude quantization of frequency spectrums of waveform data sets to identify normal and anomalous waveform signals.

Provided a method comprising: obtaining waveform data sets of a periodic electric waveform signal, with a length set to one cycle time; calculating a frequency spectrum for each waveform data set; extracting and separating odd and even frequency harmonics to create odd and even frequency harmonic matrices on which a canonical correlation analysis (CCA) being applied to obtain CCA features; performing linear transformation on the CCA features to obtain linear transformed features; generating a model based on the linear transformed features; performing magnitude quantization of frequency spectrums of waveform data sets to identify normal and anomalous waveform signals.

In certain aspects of the disclosure, a frequency monitor includes a counter configured to receive a monitored clock signal, to count a number of periods of the monitored clock signal over a predetermined time duration, and to output a count value corresponding to the number of periods of the monitored clock signal. The frequency monitor also includes a comparator configured to receive the count value from the counter, to receive an expected count value, to compare the count value from the counter with the expected count value, and to output a pass status signal or a fail status signal based on the comparison.

A signal inspection apparatus, a signal inspection system, a signal inspection method, and a non-transitory computer-readable medium encoded with a signal inspection program are provided, all of which can appropriately detect discrepancy between multiplexed signals. A signal inspection apparatus includes: an acquisition unit that acquires values of at least two signals among multiplexed signals in a predetermined cycle; a count unit that counts respective changes in the at least two signals in a predetermined time frame; a calculation unit that calculates a difference between the counts of changes; and an output unit that performs an output indicating discrepancy between the signals, if the difference between the counts of changes exceeds an allowable value.

A signal inspection apparatus, a signal inspection system, a signal inspection method, and a non-transitory computer-readable medium encoded with a signal inspection program are provided, all of which can appropriately detect discrepancy between multiplexed signals. A signal inspection apparatus includes: an acquisition unit that acquires values of at least two signals among multiplexed signals in a predetermined cycle; a count unit that counts respective changes in the at least two signals in a predetermined time frame; a calculation unit that calculates a difference between the counts of changes; and an output unit that performs an output indicating discrepancy between the signals, if the difference between the counts of changes exceeds an allowable value.

A frequency detection device for a clock signal and a detection method thereof are provided. The frequency detection device includes a pulse signal generator, a sampling signal generator, a delay device, and a sampling circuit. The pulse signal generator detects a plurality of transition edges of the clock signal and generates a pulse signal according to the transition edges of the clock signal. The sampling signal generator generates a sampling signal based on a command signal according to pluses of the pulse signal. The delay device delays the command signal to generate a delayed command signal. The sampling circuit samples the delayed command signal according to the sampling signal to generate a detection result.