HACH GLI Non-Contacting (Inductive) Conductivity Analyzer

Overview

The HACH GLI Non-Contacting (Inductive) Conductivity Analyzer is an industrial-grade online measurement system engineered for continuous, maintenance-free monitoring of conductivity, total dissolved solids (TDS), and percent concentration in aggressive aqueous process streams. Unlike contacting (electrode-based) sensors—prone to fouling, coating, corrosion, and calibration drift—the GLI series employs toroidal (inductive) sensor technology: two isolated coils housed within a chemically inert PEEK or PVDF body generate and detect a magnetic field proportional to solution conductivity. This principle eliminates electrode polarization, enables stable operation in high-conductivity media (up to 2 S/cm), and ensures long-term reproducibility without routine cleaning or recalibration. Designed for integration into municipal water treatment, chemical manufacturing, power plant cooling circuits, wastewater effluent monitoring, and pharmaceutical process water systems, the analyzer delivers traceable, temperature-compensated measurements compliant with ASTM D1125, ISO 7888, and USP guidelines for purified water and water for injection.

Key Features

• Three configurable transmitter variants: E53 (dual 4–20 mA outputs, NEMA 4X/IP65 panel/wall/pipe mount), E33 (compact dual-output unit for indoor panel installation), and PRO-E3 (intrinsically safe, Class I, Division 2 certified for hazardous locations)
• Wide dynamic range: 0.0–2,000,000 µS/cm conductivity, 0–9,999 ppm TDS, and 0.0–200% w/w concentration across common acids (H₂SO₄, HCl), bases (NaOH, KOH), and salts (NaCl, CaCl₂)
• Built-in concentration lookup tables with preloaded calibration curves per IEC 60788 and manufacturer-specified electrolyte models; user-definable custom curves via HACH GLI Configurator software
• Automatic linear or non-linear temperature compensation (NTC or Pt1000 input supported); selectable reference temperatures (e.g., 25°C, 20°C)
• Diagnostic capabilities include sensor health monitoring, signal-to-noise ratio evaluation, temperature sensor validation, and real-time error logging with timestamped event history
• Secure menu navigation with multi-level password protection (operator, technician, administrator); full audit trail for configuration changes per GLP/GMP requirements

Sample Compatibility & Compliance

The GLI analyzer is validated for use with conductive aqueous solutions—including corrosive, abrasive, viscous, or suspended-solid-laden streams—where traditional electrodes fail. Its toroidal sensor requires no direct electrical contact with the medium, making it suitable for caustic lye solutions (>50% NaOH), concentrated sulfuric acid, seawater desalination brines, and bioreactor nutrient feeds. All models meet CE electromagnetic compatibility (EMC) Directive 2014/30/EU and safety standard EN 61010-1. The PRO-E3 variant carries ATEX II 2G Ex db IIB T5 Gb and IECEx Ex db IIB T5 Gb certifications. When paired with HACH’s IQ SensorNet or SCADA-integrated data loggers, the system supports electronic record integrity per FDA 21 CFR Part 11, including digital signatures, user access controls, and immutable audit trails.

Software & Data Management

Configuration, calibration, and diagnostics are performed using the Windows-based HACH GLI Configurator software (v5.0+), which supports offline setup, firmware updates, and batch parameter export/import. The software generates calibration certificates compliant with ISO/IEC 17025 documentation standards. For enterprise integration, analog outputs interface directly with DCS/PLC systems (e.g., Siemens SIMATIC, Rockwell ControlLogix), while optional Modbus RTU/ASCII or HART 7 communication modules enable bidirectional data exchange. Historical trend logs (conductivity, TDS, temp, concentration) are stored locally on microSD card (E53/E33) or external historian (PRO-E3), with CSV export capability for LIMS or MES synchronization.

Applications

• Municipal drinking water: raw intake monitoring, coagulant dosing control, distribution system TDS verification
• Industrial wastewater: effluent compliance reporting (e.g., EPA NPDES permits), neutralization tank control, membrane fouling early warning
• Power generation: boiler feedwater purity assurance, condensate return monitoring, cooling tower cycles-of-concentration management
• Chemical processing: batch concentration verification, CIP rinse endpoint detection, acid/base titration support
• Pharmaceutical water systems: PW, WFI, and pure steam condensate conductivity surveillance per EU Annex 1 and USP

FAQ

How does inductive conductivity measurement differ from contacting electrode methods?
Inductive (toroidal) sensors use magnetic coupling to measure conductivity without electrode-solution contact—eliminating polarization errors, coating interference, and drift caused by electrode degradation.
Can the GLI analyzer measure concentration of non-standard electrolytes?
Yes. Users may define custom concentration curves using at least three reference points measured with laboratory-grade titration or gravimetric analysis.
Is temperature compensation mandatory for accurate readings?
Yes. Conductivity is inherently temperature-dependent; the GLI system applies automatic compensation using built-in Pt1000 or NTC sensors per DIN EN 60751 or IEC 751 standards.
What maintenance intervals are recommended for the toroidal sensor?
No scheduled maintenance is required. Visual inspection every 6–12 months is advised; cleaning is only necessary if mechanical debris obstructs the flow path—not the sensor surface.
Does the PRO-E3 model support redundant power or dual-channel output?
The PRO-E3 provides a single 4–20 mA output and operates exclusively on 16–30 VDC; redundancy requires external signal splitters or DCS-configured backup logic.