Fig. 1. Time-domain fluorescence lifetime dissolved oxygen measurement system. (a) Schematic diagram; (b) picture of real products

Fig. 2. Fluorescent signals under different excitation light intensities. (a) Original fluorescence measurement curve; (b) normalized fluorescence quenching curve

Fig. 3. Fluorescent signals at different excitation durations. (a) Original fluorescence measurement curve; (b) normalized fluorescence quenching curve

Fig. 4. Normalized fluorescence quenching curves at different mass concentrations

Fig. 5. Relationship between fluorescence lifetime and dissolved oxygen mass concentration

Fig. 6. Fitting results of fluorescence lifetime with dissolved oxygen mass concentration. (a) Stern-Volmer equation direct fit; (b) lifetime correction fit

Fig. 7. Comparison test results between experimental measurement system and HQ30d analyzer