Yokogawa Electric Corporation EXA-PH402 pH/ORP Converter

The Yokogawa EXA-PH402 pH/ORP Converter accepts dual high-impedance pH and ORP sensor signals and converts them into standardized outputs for continuous process control in industrial liquid analysis systems. It provides dual 4–20 mA outputs plus relay outputs, and includes built-in PI control via analog outputs and relays to help stabilize pH/ORP conditions in the process. The unit features an LCD interface for configuration and diagnostics, microprocessor-aided calibration with buffer tables, and sensor diagnostics that monitor impedance, stability, and response. Automatic temperature compensation adjusts for process variation, and the IP65 / NEMA 4X enclosure supports panel or field mount installations in chemical plants, water treatment facilities, and other industrial environments. Common applications include wastewater treatment, chemical processing, food and beverage production, and power generation systems requiring continuous pH and ORP monitoring. As a legacy EXA series analyzer, the PH402 is discontinued, with common replacements including the Yokogawa PH450G Converter, FLXA21, and FLXA202 pH analyzers; digital communication capability is model dependent, and the unit offers a display-based configuration and diagnostics experience alongside sensor health checks.