HACH 3700E Series Electrodeless Conductivity Probe

Overview

The HACH 3700E Series Electrodeless Conductivity Probe is a digitally enabled, toroidal (inductive) conductivity sensing platform engineered for high-reliability, maintenance-free operation in demanding industrial and municipal water quality monitoring applications. Unlike traditional two- or four-electrode contact-type sensors, the 3700E employs a non-invasive toroidal measurement principle: an excitation coil generates an alternating magnetic field that induces eddy currents in the conductive medium; a second detection coil measures the resulting current magnitude—proportional to solution conductivity—without direct electrode contact. This architecture eliminates polarization, fouling, coating, and corrosion risks inherent to electrode-based systems, delivering long-term stability and reproducibility in aggressive, high-solids, or viscous streams—including wastewater, brine, caustic cleaning solutions, and CIP rinse cycles.

Key Features

• Toroidal (electrodeless) sensing technology ensures zero drift from electrode passivation, scaling, or biofilm accumulation
• Digital HART-enabled interface for seamless plug-and-play integration with HACH SC200 or SC1000 universal controllers—no manual configuration or wiring calibration required
• Wide dynamic conductivity range (0–2,000,000 µS/cm) supports applications from ultrapure water polishing to saturated brine monitoring
• Integrated Pt1000 RTD temperature sensor with full-range compensation (−10 to +200 °C), traceable to NIST standards
• High-resolution output (0.1 µS/cm minimum resolution) and accuracy of ±0.01% of reading across all ranges—validated per ASTM D1125 and ISO 7888
• Multiple wetted-material options: PP, PVDF, PFA, and PEEK—each rated for pressure, temperature, and chemical compatibility per ANSI/ISA-71.04 G3 severity classification
• Two mechanical configurations: sanitary flanged (D3705E–D3708E) and NPT-threaded flexible-mount (D3725E–D3728E), supporting ASME BPE, 3-A, and FDA-compliant installations

Sample Compatibility & Compliance

The 3700E series is validated for continuous online measurement in heterogeneous, particulate-laden, and chemically aggressive matrices where electrode degradation compromises data integrity. It complies with EPA Method 120.1 for conductivity determination in drinking water and wastewater effluents. All models meet IP68 ingress protection, CE marking (EMC Directive 2014/30/EU and LVD Directive 2014/35/EU), and RoHS 2011/65/EU requirements. Flanged variants conform to ASME B16.5 Class 150 and 3-A Sanitary Standards #54-01. Flexible NPT versions support GMP-compliant process skids under FDA 21 CFR Part 11 when paired with SC1000 controllers featuring audit-trail-enabled firmware.

Software & Data Management

When connected to SC200 or SC1000 controllers, the 3700E probe operates within HACH’s unified Instrument Management Software (IMS), enabling remote calibration verification, sensor health diagnostics (e.g., coil impedance trending), and automated data logging at user-defined intervals (1 sec to 24 hr). Raw conductivity, TDS (calculated via NaCl equivalence), salinity (%), and temperature values are timestamped and exportable in CSV or MODBUS TCP format. Firmware updates and configuration backups are performed over Ethernet or RS-485, with change-control logs compliant with GLP and ISO/IEC 17025 documentation requirements.

Applications

• Real-time conductivity monitoring in pharmaceutical WFI and PW distribution loops
• Brine concentration control in desalination reverse osmosis pretreatment
• CIP solution strength verification in food & beverage processing lines
• Effluent salinity tracking in oilfield produced water treatment
• Electrolyte concentration feedback in electroplating bath management
• Steam condensate purity assurance in power generation HRSG systems

FAQ

Does the 3700E require periodic recalibration?
No—toroidal design eliminates electrode drift; however, annual verification against certified KCl standard solutions (e.g., 1413 µS/cm at 25 °C) is recommended per ISO/IEC 17025 clause 7.7.
Can the probe be used in pressurized pipelines?
Yes—flanged models support up to 10 bar at 200 °C; NPT versions rated to 6 bar at 120 °C (material-dependent); consult individual datasheets for pressure-temperature derating curves.
Is temperature compensation automatic?
Yes—the integrated Pt1000 RTD provides real-time linearization using either NaCl, KCl, or user-defined temperature coefficient (α) algorithms per IEC 60746-3.
What controller firmware version is required?
SC200 firmware v3.10+ or SC1000 v4.20+ is mandatory to enable full digital handshake, diagnostic reporting, and multi-parameter derivation (TDS/salinity).
How is sensor health monitored?
The controller continuously logs excitation coil impedance and signal-to-noise ratio (SNR); deviations >5% from baseline trigger configurable maintenance alerts in IMS.