Technical Specifications:

• Measurement Parameters: pH, ORP (mV)
• pH Range: -2.00 to 16.00 pH
• ORP Range: -1500 to +1500 mV
• Accuracy (pH): ±0.05 pH (at 25 °C)
• Accuracy (ORP): ±1 mV
• Resolution: 0.01 pH / 1 mV
• Temperature Range: 0 to 120 °C (32 to 248 °F)
• Temperature Compensation: Automatic (AU), 0 to 100 °C range
• Output Signal: 4–20 mA DC (2-wire loop-powered)
• Power Supply: 12 to 36 V DC (2-wire)
• Load Resistance: 0 to 600 Ω (at 24 V DC supply)
• Response Time: ≤30 seconds (pH, 95% of step change)
• Electrode Input: BNC connector, high impedance (10¹² Ω)
• Protection Rating: IP65 / NEMA 4X (front panel)
• Process Connection: 1/2″ NPT thread or flange (depending on configuration)
• Housing Material: Polycarbonate (standard), PVDF or SS316L (options)
• Display: Dual 5-digit LED display (pH/ORP + Temperature)
• Operating Temperature: -10 to 60 °C (14 to 140 °F) for transmitter electronics
• Ambient Humidity: 0 to 90% RH (non-condensing)
• Dimensions: 144 × 144 × 102 mm (W × H × D) approximately
• Weight: Approximately 1.2 kg (2.65 lb)

Functional Features:

• Automatic Temperature Compensation (ATC): Built-in temperature sensor compensates pH readings in real-time using Nernst equation
• Dual Display: Simultaneous display of pH (or ORP) and temperature on front panel
• 2-Wire Operation: Loop-powered design eliminates need for separate power supply
• Calibration: 2-point or 3-point calibration with automatic buffer recognition
• HOLD Function: Freezes display value for stable reading capture
• Alarm Outputs: 2 SPDT relay outputs (configurable high/low/deviation alarms)
• Self-Diagnostics: Electrode impedance check, slope check, and sensor life indicator

Performance Parameters:

• Input Impedance: 10¹² Ω (pH electrode)
• Isolation: 500 V AC between input and output
• EMC Compliance: EN 61326-1, EN 61000-6-2, EN 61000-6-4
• Explosion Proof Option: Available with Ex d IIC T6 / Ex ia IIC T6 certification
• SIL Rating: SIL 2 capable (with safety relay option)
• Drift: Less than ±0.02 pH per 24 hours

Structural Features:

• Wall-mount or pipe-mount installation (UM = Universal Mounting)
• Polycarbonate housing with IP65 gasket seal
• BNC connector for pH/ORP electrode
• Screw terminal block for 4–20 mA output and relay connections
• Transparent front cover with dual LED window
• DIN rail mounting bracket available as accessory

Working Principle:
The PH450G receives the millivolt signal from a pH or ORP glass electrode via the BNC input. The high-impedance input amplifier converts the electrode potential into a digital value. The internal microprocessor applies temperature compensation using the built-in temperature sensor and the Nernst equation to calculate the corrected pH value. The result is converted to a 4–20 mA output signal proportional to the measured value. The dual LED display shows both the primary measurement and temperature simultaneously.

Advantage Highlights:

• 2-Wire Loop Power: Reduces wiring costs and simplifies installation
• Built-in ATC: Eliminates need for separate temperature compensation module
• IP65/NEMA 4X Rating: Suitable for washdown and outdoor installations
• Dual Display: Operators can monitor both pH and temperature at a glance
• Low Maintenance: Self-diagnostics and electrode life indication reduce downtime
• Wide Measurement Range: -2 to 16 pH covers virtually all industrial applications

Applicable Industries:

• Water and wastewater treatment
• Chemical manufacturing
• Food and beverage processing
• Pharmaceutical production
• Pulp and paper mills
• Mining and mineral processing
• Semiconductor manufacturing
• Power plant water chemistry

Installation Requirements:

• Mount transmitter at eye level for easy display reading
• Ensure process connection is leak-tight (use Teflon tape or gasket)
• Route electrode cable away from high-voltage power cables (minimum 300 mm separation)
• Ground the transmitter housing to plant earth
• Use only Yokogawa-compatible pH electrodes (e.g., SC21V, SC25V series)
• Provide minimum 100 mm straight pipe run upstream and 50 mm downstream for representative sampling

Usage Precautions:

• Calibrate with fresh pH 4.00, 7.00, and 10.00 buffer solutions before initial use
• Clean pH electrode regularly to prevent fouling and slow response
• Do not expose the transmitter electronics to temperatures above 60 °C
• Replace pH electrode when slope falls below 85% of theoretical Nernst slope (59.16 mV/pH at 25 °C)
• Ensure loop power supply voltage is within 12–36 V DC range
• Do not disconnect the electrode while the transmitter is powered (may cause output saturation)