I. Different principles

1. Infrared spectrophotometer: The light emitted by the light source is divided into two beams with equal and symmetrical energy. One beam is the sample light passing through the sample, and the other is the reference light as a reference. After the two beams of light enter the photometer through the sample chamber, they are modulated by the sector mirror at a certain frequency to form an alternating signal. Then the two beams of light are combined into one and enter the monochromator alternately through the incident slit.

2. FTIR spectrometer: It is an infrared spectrometer developed based on the principle of Fourier transform of the interfered infrared light.

II. Different compositions

1. Near infrared spectrometer: The detector converts the above alternating signals into corresponding electrical signals. After voltage amplification by the amplifier, it is transferred to the A/D conversion unit. After computer processing, the infrared absorption spectra from high wave-number to low wave-number is obtained.

2. Fourier infrared spectrometer: It consists of an infrared light source, aperture, interferometer (beam splitter, moving mirror, fixed mirror), sample chamber, detector, various infrared reflectors, lasers, control circuit boards and power supplies.

III. Different applications

1. NIR spectrometer: widely used in petroleum, chemical industry, medicine, environmental protection, teaching, materials science and other fields.

2. Fourier transform infrared spectrometer: widely used in pharmaceutical and chemical industry, mining, petroleum, coal, environmental protection, customs, gem identification and other fields.