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当被测信号是正弦函数或其它周期性函数时,用频域法来研究和分析测量系统的动态特性要比用时域法方便和准确得多。测量系统对被测量的频率响应是指系统对正弦输入的稳态响应。由于各种变化规律的输入量均可以通过富氏变换分解成一系列具有不对同频率和幅值的正弦信号,因此,频域法在原则上适用于任意变化规律的信号。测量系统的频率响应特性主要包括幅频特性、相频特性和幅相特性,其频域性能指标也主要从上述几个特性上来定义。
When the measured signal is a sine function or other periodic function, it is more convenient and accurate to study and analyze the dynamic characteristics of the measurement system by using the frequency domain method than by the time domain method. The frequency response of the measurement system to the measured measurement refers to the steady-state response of the system to the sinusoidal input. Since the input of various laws of variation can be decomposed into a series of sinusoidal signals with different frequencies and amplitudes by the Fourier transform, the frequency domain method is applicable to a signal of any variation rule in principle. The frequency response characteristics of the measurement system mainly include the amplitude-frequency characteristic, the phase frequency characteristic and the amplitude-phase characteristic. The frequency domain performance index of the measurement system is mainly defined from the above several characteristics.