Fig. 1. Influence of setting sampling threshold on detection accuracy under different decay time and relationship between detection accuracy and ring-down time when threshold is fixed. (a) Relationship between detection accuracy and threshold; (b) relationship between detection accuracy and ring-down time when V_T=80 mV

Fig. 2. Setting threshold and ring-down time versus methane detection range. (a) Setting threshold versus methane detection range; (b) ring-down time versus methane detection range

Fig. 3. Schematic of CRDS experimental device

Fig. 4. Detection accuracy and signal-to-noise ratio at each setting threshold

Fig. 5. Thresholds and ring-down time under different methane concentrations. (a) Thresholds under different methane concentrations; (b) ring-down curve of methane standard gas with volume fraction of 1.0×10^-6 when τ=24.57 μs and V_T=238.54 mV; (c) ring-down curve of methane standard gas with volume fraction of 1.0×10^-4 when τ=1.36 μs and V_T=5.36 mV

Fig. 6. Measurement results of methane standard gas with each concentration

Fig. 7. Quoted error under different measurement ranges