Hach GLI3400 Series High-Performance Conductivity Sensors

Overview

The Hach GLI3400 Series High-Performance Conductivity Sensors are engineered for continuous, high-fidelity conductivity measurement across demanding industrial process environments—from ultrapure water systems in semiconductor and pharmaceutical manufacturing to high-temperature boiler feedwater and condensate monitoring in power generation. These sensors operate on the principle of two-electrode or four-electrode (depending on configuration) conductance measurement, where an applied AC voltage generates a current proportional to the ionic concentration of the medium. The GLI3400 platform is distinguished by its factory-determined, traceable four-digit cell constant—calibrated individually per probe—and its compatibility with Hach’s DRY-CAL methodology, enabling accurate field calibration without liquid standards. Designed for long-term stability under thermal cycling, chemical exposure, and mechanical stress, the series meets the operational rigor required for ISO 9001-certified production lines, FDA-regulated bioprocessing, and ASME B31.1-compliant steam cycle instrumentation.

Key Features

• Individually calibrated four-digit cell constant (0.05–10.0 cm⁻¹), certified and documented per unit for metrological traceability
• DRY-CAL compatible architecture—eliminates need for wet calibration solutions while maintaining NIST-traceable accuracy
• Thermally robust construction: full operational range from −20 °C to +200 °C with pressure rating up to 100 psig at maximum temperature
• Five mechanically and chemically optimized probe variants: 3422 (compression-fit), 3433 (non-metallic universal), 3444 (high-temperature), 3455 (sanitary flange), each selected for material compatibility and installation geometry
• Electrode materials include titanium (for chloride-rich or oxidizing environments), graphite (for aggressive acids or alkalis), and 316 stainless steel (for general-purpose steam/water applications)
• High-speed thermal response time (<30 s to 90% step change) ensures dynamic tracking of rapid process transients
• IP68-rated housing with integral temperature compensation (Pt1000 RTD) for simultaneous conductivity and temperature measurement

Sample Compatibility & Compliance

The GLI3400 Series supports direct insertion or flow-through measurement in liquids spanning deionized water (0.055 µS/cm), ultrapure water (UPW) used in wafer cleaning (≤0.1 µS/cm), boiler blowdown (up to 200,000 µS/cm), and seawater-influenced cooling circuits (up to 2,000,000 µS/cm). It complies with ASTM D1125 (Standard Test Methods for Electrical Conductivity and Resistivity of Water), ISO 7888 (Water quality — Determination of electrical conductivity), and USP (Water Conductivity). For regulated industries, the sensor integrates seamlessly with Hach SC1000 or HQd platforms supporting 21 CFR Part 11-compliant audit trails, electronic signatures, and data integrity protocols aligned with ALCOA+ principles. All variants meet CE marking requirements for electromagnetic compatibility (EMC Directive 2014/30/EU) and low-voltage safety (LVD Directive 2014/35/EU).

Software & Data Management

When interfaced with Hach’s IQ SensorNet or SC Series controllers, the GLI3400 delivers real-time conductivity, temperature, and calculated resistivity values via Modbus RTU/ASCII, HART 7, or 4–20 mA analog output. Firmware supports automatic temperature compensation using either linear (α = 2.0 %/°C default) or non-linear (NaCl or KCl reference curve) algorithms. Data logging intervals are configurable from 1 second to 24 hours, with onboard memory retaining ≥30 days of timestamped readings. Hach’s LogR software enables export to CSV, PDF reports, and integration into MES/SCADA systems via OPC UA. Calibration history—including date, operator ID, DRY-CAL checksum, and deviation from baseline—is retained and exportable for GLP/GMP audits.

Applications

• Power generation: Condensate polishing, turbine bypass monitoring, and drum-level conductivity control per EPRI guidelines
• Pharmaceutical manufacturing: UPW distribution loop surveillance per EU GMP Annex 1 and USP , WFI point-of-use verification
• Food & beverage: CIP rinse water validation, syrup dilution control, and pasteurizer leak detection
• Semiconductor fabs: Chemical delivery system purity assurance and megasonic bath monitoring
• Municipal and industrial wastewater: Effluent salinity screening, membrane fouling early warning, and desalination brine management
• Chemical processing: Reaction endpoint detection in neutralization or hydrolysis processes

FAQ

How is the cell constant determined and verified?
Each GLI3400 sensor undergoes individual calibration against NIST-traceable KCl standard solutions at 25 °C in Hach’s ISO/IEC 17025-accredited laboratory; the resulting four-digit constant is laser-etched on the probe body and stored in its digital memory.
Can the GLI3400 be used in sanitary applications requiring 3-A or EHEDG certification?
Yes—the 3455 sanitary flange variant is constructed with electropolished 316L SS, meets 3-A SSI Standard 68-03 for dairy equipment, and carries EHEDG Document 8 compliance for hygienic design.
What maintenance is required to sustain accuracy over time?
No routine recalibration is needed if DRY-CAL is performed annually; physical inspection for coating, erosion, or seal integrity is recommended per IEC 61511 functional safety intervals.
Is temperature compensation automatic and configurable?
Yes—integrated Pt1000 RTD provides real-time compensation; users may select between fixed α, NaCl, or custom polynomial curves via controller interface.
Does the probe support hazardous area installation?
The 3422 and 3444 models are available with ATEX/IECEx certification (II 1G Ex ia IIC T4 Ga) for Zone 0 gas environments when paired with approved intrinsic safety barriers.