Modulation variable amplitude broadband weak signal conditioning method and optical filter type near infrared moisture meter

The invention belongs to the field of detection. The method comprises the following steps: acquiring an amplitude-variable broadband direct-current signal f1 (t) converted by a sensor of an optical filter light splitting type near-infrared spectrometer; carrying out amplification and amplitude demodulation on the amplitude-variable broadband direct current signal f1 (t) to obtain an amplitude-variable broadband alternating current signal f2 (t); k-order Fourier harmonic coefficients of the amplitude-variable broadband direct-current signal f1 (t) and the amplitude-variable broadband alternating-current signal f2 (t) are solved, amplitude-frequency conversion and phase-frequency conversion of the Fourier coefficients are carried out, and the mode and the phase of a transfer function Hk (omega) of the band-pass filter are designed to be consistent with those of first 100-order harmonics of Fk (omega) except for a frequency abrupt change point; the signal is conditioned and amplified, signal conditioning is comp