- Model: Yokogawa EXA PH402 / PH402G-E-1-E/Q/PM
- Brand: Yokogawa
- Series: EXA PH Series Analytical Measurement Platform
- Core Function: Converts and processes pH/ORP sensor signals for industrial process control
- Product Type: pH/ORP Converter Analyzer
- Key Specs: Dual sensor compatibility, 4–20 mA output, HART communication
- Supply Status: ⚠️ Legacy analyzer platform, availability subject to inventory confirmation
- Stock: Available (New Surplus inventory)
- Warranty: 12 months
- Ship From: China / Singapore / EU
- Condition: Brand New Surplus (Original industrial inventory, not refurbished)
The Yokogawa EXA PH402 is an industrial liquid analytical converter designed for continuous pH and ORP measurement in demanding process environments.
Unlike portable laboratory meters, this unit is built for:
- 24/7 continuous operation,
- integration into DCS/PLC systems,
- and long-term field installation.
Typical installations include:
- chemical dosing systems,
- boiler water treatment,
- wastewater plants,
- semiconductor ultrapure water,
- and pulp & paper processes.
有一点要注意，现场很多 pH 问题其实不是变送器坏了，而是电极老化、接地不好、或者安装位置不合理。
The converter itself is usually quite stable.
Key Technical Specifications
- Measurement Type: pH and ORP measurement
- Input Compatibility: Glass electrode and reference electrode sensors
- Display Type: LCD digital display with menu navigation
- Output Signal: 4–20 mA isolated analog output
- Communication Protocol: HART communication supported on selected versions
- Power Supply: 100–240 V AC or 24 V DC depending on configuration
- Mounting Method: Panel, wall, or pipe mounting
- Protection Rating: IP65 / NEMA-rated enclosure
- Temperature Compensation: Automatic and manual compensation supported
- Calibration Modes: Automatic buffer calibration and manual calibration
- Relay Functions: Alarm and cleaning control relay outputs
- Operating Temperature: Industrial extended operating range
- Sensor Diagnostics: Electrode impedance and sensor condition monitoring
- Application Media: Water, wastewater, chemical solutions, process liquids
Installation & Configuration Guide
Pre-Installation Preparation (Estimated Time: 20–30 Minutes)
⚠️ pH analyzers are sensitive measurement devices.
Improper grounding or cable routing can create unstable readings.
Before installation:
- Confirm process compatibility:
- liquid conductivity,
- temperature,
- chemical compatibility,
- and pressure conditions
- Verify electrode condition before connecting converter
- Prepare installation location:
- avoid strong vibration,
- avoid direct sunlight,
- avoid high electromagnetic interference areas
Required tools:
- Fluke multimeter
- Shielded signal cable
- Calibration buffer solutions (pH 4, 7, 10)
- Insulation tester
- Small screwdriver set
From experience, grounding quality affects pH stability more than people expect.
A noisy ground can make readings drift constantly.
Removal of Existing Unit (Estimated Time: 15–20 Minutes)
- Isolate analyzer power supply
- Disconnect sensor wiring carefully
- Label terminal connections before removal
- Remove old converter from panel or mounting bracket
- Inspect electrode cable condition
⚠️ Never pull sensor cables aggressively.
Glass electrodes are fragile and expensive.
Installation Procedure (Estimated Time: 30–45 Minutes)
- Verify exact model and power configuration
- Mount converter securely
- Connect power supply wiring
- Connect sensor cables according to terminal diagram
- Verify shield grounding on signal cables
Configuration steps:
- Select measurement mode:
- pH,
- ORP,
- temperature compensation
- Configure output scaling:
- 4 mA = low range
- 20 mA = high range
- Configure relay alarms:
- high pH,
- low pH,
- sensor failure
- Perform initial calibration using certified buffer solution
⚠️ Calibration should occur after sensor stabilization, not immediately after immersion.
