HACH Digital Electrodeless Conductivity Sensor Series 3700

Overview

The HACH Digital Electrodeless Conductivity Sensor Series 3700 is an industrial-grade, maintenance-optimized solution engineered for continuous, high-stability conductivity measurement in demanding online water quality monitoring applications. Unlike conventional two- or four-electrode contact sensors, the 3700 series employs toroidal (inductive) electrodeless technology—where alternating current induces eddy currents in the conductive medium via a primary coil, and a secondary coil detects the resulting magnetic field strength. This non-contact principle eliminates electrode fouling, polarization errors, and calibration drift associated with surface-contact electrodes, delivering long-term signal stability in wastewater, ultrapure water, pharmaceutical process streams, and food & beverage rinse cycles. The sensor operates natively in digital mode and integrates seamlessly with HACH’s SC100 or SC1000 universal digital controllers without manual configuration—enabling true plug-and-play deployment in fixed-mount or portable monitoring stations.

Key Features

• Digital-native architecture with embedded sensor identification (ID) chip—automatically recognized upon insertion into SC100/SC1000 controllers, eliminating manual parameter entry or wiring mapping.
• Toroidal induction design ensures zero electrode corrosion, no electrolyte leakage, and immunity to coating, scaling, or biofilm interference—critical for low-conductivity ultrapure water (e.g., ≥0.055 µS/cm at 25 °C) and high-solids wastewater streams.
• Modular mechanical configurations: Available with either 2-inch sanitary clamp (D3705–D3708) or 2-inch NPT threaded (D3725–D3728) process connections to support hygienic, chemical-resistant, or high-pressure installations.
• Chemically inert wetted materials—including PP, PVDF, PFA, and PEEK—certified for FDA-compliant and USP Class VI applications; compatible with CIP/SIP protocols in biopharma and dairy processing.
• Factory-calibrated and pre-compensated for temperature (via integrated Pt1000 RTD), supporting automatic linearization per ISO 7888 and ASTM D1125 conductivity–temperature algorithms.

Sample Compatibility & Compliance

The 3700 series is validated for use across a broad conductivity range (0.055 µS/cm to 2 S/cm), accommodating deionized water, boiler feedwater, cooling tower blowdown, activated sludge effluent, and clean-in-place (CIP) rinse solutions. All variants comply with international water quality standards including ISO 7888 (electrical conductivity of water), ASTM D1125 (standard test methods for electrical conductivity of water), and USP (water conductivity testing for pharmaceutical use). The digital interface supports audit-ready data integrity: timestamped measurements, sensor diagnostics (e.g., coil impedance, signal-to-noise ratio), and firmware version logging—all traceable under GLP/GMP environments requiring 21 CFR Part 11–compliant electronic records when paired with SC1000 controller’s optional data logging module.

Software & Data Management

When connected to SC100 or SC1000 controllers, the 3700 sensor feeds real-time conductivity and temperature data into HACH’s Unified Configuration Software (UCS) or enterprise-level SCADA platforms via Modbus RTU/ASCII or HART 7 protocols. UCS enables remote firmware updates, diagnostic history review, and calibration verification reports—including deviation tracking against factory reference values. For regulatory environments, SC1000’s optional “Audit Trail” feature logs all user-initiated changes (e.g., range reconfiguration, zero adjustment) with operator ID, timestamp, and pre-/post-values—supporting FDA 21 CFR Part 11 and EU Annex 11 compliance. Raw sensor output is delivered as IEEE 754 32-bit floating-point values, ensuring metrological traceability without analog-to-digital conversion loss.

Applications

• Real-time conductivity monitoring in pharmaceutical water-for-injection (WFI) and purified water (PW) distribution loops.
• Concentration control of acid/base cleaning solutions in food & beverage CIP systems.
• Effluent discharge compliance monitoring per local environmental regulations (e.g., EPA NPDES permits).
• Reverse osmosis (RO) and electrodeionization (EDI) system performance validation.
• Bioreactor nutrient media conductivity trending during upstream processing.

FAQ

How does electrodeless (toroidal) conductivity measurement differ from traditional electrode-based sensors?
Toroidal sensors use electromagnetic induction rather than direct electrical contact—eliminating polarization, coating sensitivity, and electrolyte depletion issues inherent in contacting electrodes.
Can the 3700 sensor be used in ultrapure water applications below 1 µS/cm?
Yes—the D3705E2T and D3706E2T variants are specifically optimized for low-conductivity ranges down to 0.055 µS/cm with enhanced signal-to-noise ratio and temperature compensation accuracy.
Is the digital interface compatible with third-party PLCs or SCADA systems?
Yes—via Modbus RTU/ASCII over RS-485; full register map and protocol documentation are available in HACH’s Integration Guide v3.2.
Does the sensor require periodic recalibration in the field?
No routine recalibration is required; however, annual verification using NIST-traceable standard solutions (e.g., KCl 0.01 mol/L at 25 °C) is recommended for audit compliance.
What is the maximum operating pressure and temperature rating for the PFA-bodied D3708E2T model?
Rated for continuous operation up to 6 bar (87 psi) and 120 °C with 2″ sanitary clamp connection—validated per ASME BPE-2022 for single-use and reusable bioprocessing systems.