Harmonic distortion analyzers are used to measure harmonic distortion, which occurs when a nonlinear electronic component introduces harmonics into an output waveform, distorting it from the sinusoidal input waveform. There are three main types of harmonic distortion: frequency distortion due to different amplification of different frequencies, amplitude distortion from additional harmonics generated, and phase distortion from phase shifts of different frequencies caused by energy storage elements.

13. Harmonic Distortion Analyzers:
Harmonic Distortion:
When we give a sinusoidal signal input to any electronic
instrument there should be output in sinusoidal form, but
generally the output is not exactly the replica of input, because
of various types of distortion that my occur.
Distortion is occur due to inherent non-linear characteristics
of different components used in electronic circuit. Nonlinear
behavior of electronic component introduces harmonics in the
output waveform and the resultant distortion is often referred
as harmonic distortion.

14. Types Of Harmonic Distortion:
1) Frequency Distortion:
This type of distortion occurs in amplifiers because of
amplification factor of amplifier is different for different
frequencies.
2) Amplitude Distortion:
It occurs because amplifier introduces harmonic of
fundamental of input frequency. Harmonics always generates
distortion in amplitude. E.g. when amplifiers are overdriven it
clips the waveform.
3) Phase Distortion:
This distortion occurs due to energy storage elements in the
system which causes the output signal to be displaced in phase
with the input signal. Signals with different frequencies will be
shifted by different phase angles.