NovaSulf - Model HG400 Series - Process H2S Analyser Datasheet

A reel of paper tape impregnated with lead acetate is exposed to the gaseous process sample in the sample chamber. Hydrogen sulphide (H₂S) in the process sample reacts with the lead acetate, after acidification, to form lead sulphide (PbS), a brown compound that stains the tape. The higher the concentration of H₂S the darker the stain. A focused LED and single photo detector measures the darkening stain and the analyser reports this as a 4-20mA output of the concentration of H₂S.
Incremental measurements are made on the same spot until saturation occurs, when the tape is advanced to a fresh portion of tape. This avoids the need for frequent zero or span calibrations.