Model Number Breakdown:

• PH450G: pH/ORP transmitter, 2-wire, glass electrode type
• AA: Analog output + HART, standard configuration (glass electrode, no display)
• UM: USB modem for local HART communication via USB

Key Specifications:

• Measurement Parameters: pH and ORP (mV)
• pH Range: -2.00 to 16.00 pH
• ORP Range: -1500 to +1500 mV
• pH Accuracy: ±0.005 pH (at 25 °C, with standard buffer)
• ORP Accuracy: ±1 mV (at 25 °C)
• Resolution: 0.001 pH / 0.1 mV
• Output Signal: 4–20 mA DC (HART 7 superimposed, 1200/2200 Hz)
• Temperature Compensation: Automatic (ATC) via built-in Pt1000 RTD; range -10 to 130 °C
• Isolation: Input-to-output: 1500 V AC; Input-to-power: 1500 V AC
• Loop Power Supply: 12–45 V DC (typical 24 V DC)
• Power Consumption: ≤ 20 mA (at 24 V DC, including HART communication)
• Communication: HART 7 (digital); USB modem for local PC connection (UM option)
• Response Time (T90): ≤ 30 seconds (pH, with standard electrode); ≤ 10 seconds (ORP)

Functional Features:

• 2-Wire Operation: Both power and signal transmitted over a single pair of wires — reduces cabling cost
• Auto-Calibration: Supports 1-point, 2-point, and 3-point calibration with automatic buffer recognition
• Diagnostic Alerts: Electrode slope monitoring, reference junction status, sensor end-of-life warning
• Hold Function: Configurable measurement hold on signal loss or communication failure
• Damping: Adjustable 0–60 seconds signal damping to filter noise
• Temperature Compensation: Built-in Nernst equation-based ATC with adjustable temperature coefficient

Material Composition:

• Sensor Body: SS316L stainless steel (wetted parts)
• Electrode: Glass pH electrode with Ag/AgCl reference system; Pt1000 RTD for temperature
• Cable Entry: PG13.5 cable gland (IP68 rated when fitted)
• Housing: Polycarbonate + PBT blend (UL94 V-0 rated)
• Cable: 10 m PVC-jacketed shielded cable (standard); options up to 100 m

Structural Characteristics:

• Form Factor: In-line / immersion / panel-mount configuration
• Dimensions (Transmitter Head): 80 mm (Ø) × 210 mm (L) (approximate)
• Weight: Approximately 1.2 kg (with 10 m cable)
• Process Connection: G 1/2″ BSP male thread (standard); NPT 1/2″ optional
• Protection Rating: IP68 (with cable gland properly fitted)

Operating Principle:
The glass pH electrode generates a millivolt potential proportional to the hydrogen ion activity in the process solution, following the Nernst equation (≈ 59.16 mV/pH at 25 °C). The ORP electrode (platinum/gold ring) generates a potential proportional to the oxidation-reduction state of the solution. The transmitter’s internal high-impedance amplifier measures this millivolt signal, applies temperature compensation using the Pt1000 RTD reading, and linearizes the output to a 4–20 mA DC signal. The HART 7 protocol modulates digital data onto the 4–20 mA loop for remote configuration, diagnostics, and calibration.

Advantages & Highlights:

• Ultra-High Accuracy: ±0.005 pH — among the highest in the 2-wire transmitter class
• Low Maintenance: Built-in diagnostics provide early warning of electrode degradation
• Simple Wiring: True 2-wire, loop-powered design eliminates need for separate power supply
• USB Local Access: UM option enables on-site configuration without HART modem

Applicable Industries:

• Water & Wastewater Treatment
• Chemical & Petrochemical Processing
• Pharmaceutical & Biotechnology
• Food & Beverage
• Power Generation (Boiler Water Chemistry)
• Mining (Leach Process Control)

Installation Requirements:

• Install in a location with adequate flow velocity (≥ 0.3 m/s) to ensure representative sampling
• Mount the transmitter head vertically or at an angle — never upside down (to keep reference junction wet)
• Use shielded cable; ground the shield at the transmitter end only
• Ensure minimum 300 mm immersion depth for the electrode in the process stream
• Provide 24 V DC loop power with sufficient capacity (≥ 25 mA)

Usage Precautions:

• Never dry-run the glass electrode — the glass membrane must remain hydrated at all times
• Calibrate with fresh, certified buffer solutions (pH 4.00, 7.00, 10.00) at least every 3 months
• Do not expose the electrode to HF (hydrofluoric acid) or strong alkaline solutions (> pH 12) for extended periods — glass dissolution will occur
• Replace the electrode when the slope falls below 85% of theoretical Nernst value (≈ 50.2 mV/pH)
• Do not install in locations with vibration exceeding 5 g RMS — may damage the glass bulb