GreenPrima pH120T Online pH Sensor for Secondary Urban Water Supply

Overview

The GreenPrima pH120T is a rugged, industrial-grade online pH sensor engineered specifically for continuous monitoring of pH in secondary urban water supply systems. Designed according to the electrochemical principle of potentiometric measurement using a glass membrane electrode and Ag/AgCl reference system, the pH120T delivers stable, drift-resistant output under dynamic hydraulic conditions typical of pressurized distribution networks, booster stations, and rooftop tank outlets. Its robust construction integrates a double-junction reference system with gel-filled electrolyte and ceramic junction—optimized to resist clogging from suspended solids, biofilm accumulation, and low-conductivity fluctuations common in post-treatment municipal water streams. Unlike general-purpose lab electrodes, the pH120T features a reinforced PPS (polyphenylsulfone) body and chemical-resistant EPDM O-rings, ensuring long-term integrity in chlorinated, low-TDS water matrices where conventional sensors exhibit calibration drift or junction poisoning.

Key Features

• Double-junction, gel-filled Ag/AgCl reference system with ceramic frit junction—designed to minimize contamination and maintain stable liquid junction potential in turbid or particulate-laden water
• High-precision pH-sensitive glass membrane with low-temperature coefficient (<0.003 pH/°C), enabling accurate compensation across typical urban water temperature ranges (5–40 °C)
• Integrated Pt1000 temperature sensor (DIN EN 60751 Class B) for automatic temperature compensation—calibrated traceably to NIST standards
• IP68-rated housing with 3/4″ NPT threaded process connection—suitable for direct insertion into pressurized pipelines or submersible mounting in storage tanks
• Wide operating pH range: 0–14, with optimal linearity and repeatability between pH 4.0–9.5—the critical range for regulatory compliance in drinking water distribution (per WHO Guidelines and EPA 811-B-09-001)
• Output signal: 4–20 mA (HART 7.5 compatible) or RS-485 Modbus RTU—enabling seamless integration with SCADA, DCS, and PLC-based control systems

Sample Compatibility & Compliance

The pH120T is validated for use in secondary water supply applications meeting national and international drinking water quality standards—including China’s GB 5749-2022, EU Directive 98/83/EC, and WHO Guidelines for Drinking-water Quality (4th Ed.). It demonstrates high reproducibility in water matrices with turbidity up to 100 NTU, total suspended solids (TSS) ≤ 50 mg/L, and residual chlorine ≤ 2 mg/L as Cl₂. The sensor complies with ISO 15839:2019 (Water quality — Sensors for online monitoring — Performance requirements and testing procedures) and meets electromagnetic compatibility (EMC) requirements per IEC 61326-1:2020. Its materials of construction—PPS body, borosilicate glass membrane, and food-grade EPDM seals—are certified compliant with NSF/ANSI Standard 61 for drinking water system components.

Software & Data Management

When paired with the GreenPrima PM8200P intelligent pH controller, the pH120T supports full audit-trail functionality compliant with GLP and GMP data integrity principles. The embedded firmware records timestamped calibration events (including buffer values, slope, and offset), sensor diagnostics (junction resistance, asymmetry potential), and real-time stability metrics (e.g., 5-minute standard deviation < ±0.02 pH). All logged data are exportable via USB or Modbus TCP in CSV format. The controller’s dual-language interface (English/Chinese) supports configurable alarm thresholds, hysteresis settings, and automatic recalibration scheduling—all traceable and password-protected per FDA 21 CFR Part 11 requirements for electronic records.

Applications

• Real-time pH monitoring at secondary pump station discharge points to verify post-chlorination stability
• In-line verification of corrosion control efficacy in cast iron and ductile iron distribution pipes
• Regulatory compliance reporting for municipal water utilities under China’s “Urban Water Supply Quality Supervision and Management Regulations”
• Early detection of leaching events from aging infrastructure (e.g., lead or copper solubility shifts linked to pH excursions)
• Integration with automated dosing systems for lime or CO₂ correction in centralized pressure zones
• Long-term trend analysis for asset management programs assessing pipe material degradation kinetics

FAQ

What distinguishes the pH120T from standard pH110T electrodes?

The pH120T features an enhanced double-junction reference design with optimized electrolyte flow dynamics and a larger surface-area ceramic junction—specifically engineered to sustain accuracy in high-turbidity, low-conductivity secondary water with intermittent sediment resuspension.
Is temperature compensation mandatory for secondary water applications?

Yes. Temperature-induced pH shift in low-ionic-strength water exceeds 0.02 pH/°C; integrated Pt1000 compensation is required to meet ISO 15839 accuracy class A (±0.1 pH) under field conditions.
Can the pH120T be calibrated in situ without removal from the pipeline?

Yes—zero and span calibration is supported via the PM8200P controller using standard buffer solutions (pH 4.01, 7.00, 10.01) introduced through a dedicated calibration port or via flow-through cell configuration.
What maintenance interval is recommended for continuous operation?

Visual inspection and cleaning every 3 months; full calibration verification every 6 months; reference electrolyte replacement annually—per ISO 15839 preventive maintenance guidelines.
Does the sensor comply with cybersecurity requirements for smart water infrastructure?

The HART and Modbus interfaces support secure network segmentation; firmware updates require physical USB access—aligning with IEC 62443-3-3 SL1 baseline security controls for Level 1 field devices.