Blueprint: Clinic Water Witness Photometer — Build and Implementation Specification

Build and implementation specification for the low-cost dual-channel clinic photometer (US $37.90 in parts) designed in the source paper: 525 nm DPD free-chlorine channel and 860 nm 90-degree turbidity channel, with parts list, optical and electronic design point, assembly sequence, the daily calibration protocol its accuracy budget requires, operating procedure with three-valued verdicts, and failure modes. DESIGN BLUEPRINT — SIMULATED, NOT MEASURED — NOT BUILT, NOT CLINICALLY TESTED. Blueprint for the design published as DOI 10.5281/zenodo.24109103.