Vol. 11, Issue 9, Part D (2025)

Abstract
H₂S sensing method using photodiode, LED and copper acetate is reported. In order to directly convert the output signal of optical H₂S sensing system consisted of LED and photodiode module to electrical signal, a copper acetate film coated on glass is used. The experimental results show that the sensitivity and linearity of sensor are improved as the thickness of the copper film increases. The linearity of concentration-voltage characteristics is good in range from 1 to 50 ppm at 15 ℃. The sensitivity of this sensor is 0.2-0.4v/1 ppm and the voltage at LPDM (LED photodiode module) represents the concentration of H₂S. Four times repetition is also recorded, which all demonstrate the good stability and repeatability of this system.