Application of Digital Quadrature Lock-in Amplifier in TDLAS Humidity Detection

The linearity and the stain resistance of existing humidity sensor is poor, which exists the problems such as low resolution at low temperatures, low faded wet in high humidity environment, large measurement error and long response time. Tunable diode laser absorption spectroscopy technology is studied to measure the environmental humidity, and digital quadrature lock-in amplifiers are used to extract the first harmonic signal and the second harmonic signal, which can eliminate the influence of the phase delay angle and can improve the detection accuracy of the system. Comparative experiment between TDLAS humidity sensor and R.M.YOUNG humidity sensor was completed in the lab, experimental results show that the consistency of the humidity data is very good, which can proves the validity of the TDLAS humidity measurement technology.