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Improving the Stability of Tunable Diode Laser Sensor for Natural Gas Leakage Monitoring

Tunable diode laser absorption spectroscopy (TDLAS) is a method of using a tunable diode laser scanning one of absorption lines of trace gas, this technique has advantage of high sensitivity, fast response, multi-component and non-contact measurement. We had already developed a TDLAS sensor for monitoring natural gas leakage during the natural gas production and the process of gathering and transportation in the natural gas station, but in the practical application we found that the TDLAS sensor was influenced by visibility changes. In order to overcome this interference and improve sensor stability, we present an automatic control circuit to process photoelectric signal for eliminating interference of visibility changes. Long-term monitoring results show that the concentration of CH4 are regular and stable during the natural gas production and transmission, therefore the application of the automatic gain circuit improved the stability of the TDLAS sensor.