Hach Pure Water pH Meter FAR-201A/GSU-202 Integrated Flow-Through Electrochemical Sensor System
| Brand | Hach |
|---|---|
| Origin | USA |
| Manufacturer Type | Original Equipment Manufacturer (OEM) |
| Import Status | Imported |
| Model | FAR-201A/GSU-202 |
| Instrument Type | Portable Flow-Through pH Analyzer |
| Parameter Capability | Multi-Parameter (pH, temperature, optional conductivity) |
| Measurement Accuracy | ±0.01 pH |
| Measurement Range | 0–14 pH |
| Resolution | 0.01 pH |
| Calibration Options | 1-, 2-, or 3-point calibration using standard buffers at pH 1.00, 4.01, 7.00, 9.18, 10.01, and 12.00 |
Overview
The Hach FAR-201A/GSU-202 is a purpose-engineered flow-through electrochemical sensor system designed specifically for high-accuracy, low-conductivity pure water pH measurement in power generation, semiconductor ultrapure water (UPW) loops, pharmaceutical water-for-injection (WFI) distribution systems, and laboratory-grade deionized water applications. Unlike conventional immersion-style pH meters, this system employs a dual-fluidic architecture based on the principle of continuous-flow liquid junction stabilization. It integrates a dedicated reference electrode module (FAR-201A) with a circulation-compatible glass pH sensing element (GSU-202), enabling precise potentiometric measurement under conditions where conventional electrodes suffer from high electrical resistance, slow response, and junction potential drift. The core innovation lies in its active reference fluid delivery: a peristaltic reagent pump continuously supplies saturated KCl reference electrolyte to the liquid junction, where it mixes with the sample stream just prior to the measurement interface—ensuring stable junction potential, eliminating sample contamination of the reference compartment, and maintaining thermodynamic equilibrium across the entire measurement cycle.
Key Features
- Integrated flow-through design eliminates air bubbles, stagnation, and boundary layer effects common in static immersion measurements.
- Active reference electrolyte delivery via calibrated peristaltic pump ensures consistent liquid junction potential (<1 mV drift over 72 h).
- Self-cleaning flow path: continuous sample circulation prevents particulate buildup and biofilm formation; no manual flushing or maintenance required between measurements.
- Temperature-compensated pH output with integrated Pt1000 RTD sensor (±0.1 °C accuracy) for automatic Nernstian correction.
- Modular architecture supports future expansion with optional conductivity or dissolved oxygen modules via shared analog/digital I/O interface.
- IP65-rated enclosure with corrosion-resistant 316L stainless steel wetted parts and PEEK/PTFE fluidic components for long-term reliability in cleanroom and utility tunnel environments.
Sample Compatibility & Compliance
The FAR-201A/GSU-202 is validated for use with ultrapure water (UPW) having conductivity ≤0.1 µS/cm, resistivity ≥18.2 MΩ·cm at 25 °C, and total organic carbon (TOC) <1 ppb. It complies with ASTM D1125–22 (Standard Test Methods for Electrical Conductivity and Resistivity of Water), ISO 3696:1987 (Water for analytical laboratory use), and USP (Water Conductivity). Its calibration traceability aligns with NIST-traceable pH buffer standards (NIST SRM 186, 187, 191, 192), and the system supports audit-ready calibration logs compliant with FDA 21 CFR Part 11 requirements when paired with Hach’s DataStream™ software.
Software & Data Management
Data acquisition and configuration are managed through Hach’s DataStream™ PC software (v4.2+), which provides real-time trend visualization, automated calibration validation reports, and configurable alarm thresholds (e.g., pH deviation >±0.03 from setpoint triggers event logging). All measurement data—including timestamped raw mV values, temperature, calibration history, and pump duty cycle—are stored in encrypted SQLite databases with SHA-256 integrity checksums. Export formats include CSV, PDF summary reports, and XML for LIMS integration. Audit trails record user ID, action type, timestamp, and pre-/post-value changes—fully supporting GLP and GMP documentation requirements.
Applications
- Continuous monitoring of boiler feedwater and condensate return lines in fossil and nuclear power plants.
- In-line pH verification during UPW polishing stages (e.g., post-EDI, pre-UV oxidation) in semiconductor fab utilities.
- Real-time release testing of WFI and Purified Water (PW) in pharmaceutical manufacturing suites (Annex 1-compliant).
- Validation of reverse osmosis and electrodeionization system performance in central utility plants.
- Research-grade characterization of low-ionic-strength colloidal dispersions and nanoparticle suspensions where conventional pH probes exhibit hysteresis.
FAQ
What distinguishes the FAR-201A/GSU-202 from standard portable pH meters?
It is not a handheld meter but a process-integrated flow cell system—designed for permanent installation in pressurized, low-flow water loops with zero dead volume and active reference management.
Can it be used for non-pure water samples (e.g., wastewater or seawater)?
No—its optimized junction geometry and low-sample-resistance electronics are calibrated exclusively for ultralow-conductivity matrices; use outside 0.05–1.0 µS/cm range invalidates accuracy claims.
Is third-party calibration verification supported?
Yes—Hach provides certified calibration certificates (ISO/IEC 17025 accredited) and offers on-site verification services with documented uncertainty budgets per ISO/IEC 17025:2017 Annex A.
How often does the reference electrolyte require replacement?
Under continuous operation at 50 mL/h flow rate, the 500-mL reservoir lasts ≥30 days; automated low-volume alerts trigger at 10% remaining capacity.
Does the system meet SIL2 functional safety requirements?
When configured with redundant sensors and connected to a certified safety PLC (e.g., Siemens S7-1500F), the measurement channel meets IEC 61511 SIL2 for pH-based shutdown interlocks in steam cycle chemistry control.
