Hydrogen sulfide monitoring system

Claim 1

Apparatus for monitoring hydrogen sulfide hazard potential and hydrosulfide content of well drilling mud, comprising sensor means for providing voltage potential signals representative of hydrogen ion concentration, sulfide ion concentration, and temperature of the drilling mud, transmitter means for converting said voltage signals to analog current signals while drawing a constant bias current, and producing a return current signal, cable means for conducting said analog, bias and return current signals including means for filtering said analog signals, and control means for providing said current and current signals to and from said transmitter means, said power supply and control means comprising translator filter means for converting said signals to voltage signals, filtering said signals, and converting said voltage signals to provide filtered analog pH, pS = and temperature current signals, means for combining said pH and pS = signals to provide a hazard potential signal pHP representative of H 2 S gas potentially at equilibrium with the mud, means for combining said pH and pS = signals to provide a pHS - signal representative of hydrosulfide ion concentration of the mud, means for temperature compensation of the pHP signal by temperature responsive gain control about the isoelectric point of said pHP signal, and means for temperature compensation of the pHS - signal by temperature responsive gain control about the isoelectric point of said pHS - signal.