Main functional modules of ITLA-1000xx includes transmitter, receiver, reference unit and measurement unit. The transmitter drives the tunable diode to
emit laser of certain wavelengths, which passes through the gas cell, then reaches the receiver. The receiver performs signa processing to obtain
Second harmonic signal, then calculates the processing to obtain second harmonic signal, then calculates the concentration according to
the relationship between the second harmonic signal and the gas concentration.