Principle of Operation
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The 3700E Series encapsulated electrodeless conductivity sensors induce a current in a closed loop of solution and then measure the magnitude of the current to determine the conductivity of the solution. The conductivity sensor drives Coil A, which induces an alternating current in the solution; Coil B detects the magnitude of the induced current, which is proportional to the conductivity of the solution. The conductivity sensor processes this signal and displays the corresponding reading.
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Problems such as polarization, oil fouling, and contamination will not affect the performance of electrodeless conductivity sensors. The 3700E Series conductivity sensors feature automatic temperature compensation and can be applied to solutions with conductivity up to 2000 mS/cm and temperatures ranging from 0 to 200°C.
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The 3700E Series electrodeless conductivity sensors are available in four different water-resistant materials, offering wide applicability;
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Suitable measuring media for conductivity sensors of different materials: see attached table
Features and Benefits
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Rugged material selection, contamination-free design
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Low maintenance
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Multiple conductivity sensor mounting options, including sanitary mounting
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Wetted parts materials available in Polypropylene, PVDF, PEEK, or PFA Teflon
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Standard 20 ft integral cable
Specifications
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Measuring range: 200~2000000μS/cm
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Wetted materials: Polypropylene, PEEK, PFA Teflon®, or PVDF
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Sample temperature: -10~200℃; limited only by sensor body material and mounting hardware
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Maximum flow rate: 3 m/s
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Pressure range: Up to 200 psig at 150℃; limited only by sensor body material and mounting hardware
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Accuracy: > 500 μS/cm: ±0.5% of reading; < 500 μS/cm: ±5 μS/cm
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Weight: 0.45 kg
Spare Parts
| Spare Part Order No. | Instrument Model | Chinese Description | English Description |
|---|---|---|---|
| 3725E2T | 3700 Electrodeless Conductivity Sensor | Poly non-contact conductivity probe | Electrodeless |
| 3727E2T | 3700 Electrodeless Conductivity Sensor | PEEK non-contact conductivity probe | Electrodeless |
Ordering Guide
Source: Public information from HACH Water Quality website
Case Studies
Municipal Wastewater Treatment · Controllers and Sensors — Application Case
Site Conditions
This is a Municipal Wastewater Treatment customer whose plant is at the inlet, biological and outlet stages of a municipal plant. The main task was online water monitoring with a controller and sensor combination.
The Problem
The difficulty lies in high solids and corrosive fractions, with large diurnal flow swings; at the same time effluent parameters drift and probes foul with sludge and biofilm. Specification therefore means matching each controller channel to its sensor type.
What We Did
We took a Hach channel approach — supplying against the Hach original part numbers. Delivery was built around matching each controller channel to its sensor type, with point-by-point checks on: stable compliance with Grade 1A discharge limits and online data reporting.
Operating Outcome
In service the system performs as intended — factory-matched combinations that make faults easier to locate, with routine maintenance falling noticeably.
Food & Beverage · Controllers and Sensors — Application Case
Application Context
dosing, pasteurising, filling and CIP stages is a typical Food & Beverage duty. The project started from Controllers and Sensors, focusing on online water monitoring with a controller and sensor combination.
Process Constraints
frequent cleaning demands instruments that withstand hot CIP/SIP caustic cycles, and syrups, dairy and beverages that scale easily, under strict hygienic requirements only amplify it. The Controllers and Sensors specification must therefore cover matching each controller channel to its sensor type.
Delivery Approach
Delivery was handled as the Hach channel — supplying against the Hach original part numbers. Execution centred on matching each controller channel to its sensor type, together with food-safety and hygienic design per 3-A / EHEDG.
Field Results
Operation shows the benefit clearly — factory-matched combinations that make faults easier to locate, with confidence in this measuring point improving markedly.
Chemical & Pharmaceutical · Controllers and Sensors — Application Case
Customer Profile
The typical setting in Chemical & Pharmaceutical is reactors, metering vessels and finished-product tanks. The measuring point is Controllers and Sensors; the focus is online water monitoring with a controller and sensor combination.
Key Difficulties
Conditions are highly corrosive media with solvents and crystallisation, partly in explosive atmospheres and, on top of that, corrosion plus Ex protection shortens instrument life and makes downtime costly, which a standard configuration cannot handle for long. The design therefore starts with matching each controller channel to its sensor type.
Implementation
The scope ran through the Hach channel: supplying against the Hach original part numbers. Technically it hinges on matching each controller channel to its sensor type, and on these requirements: Ex certification and GMP traceability of records.
Customer Benefit
In practice this means factory-matched combinations that make faults easier to locate, which cut the workload on the site maintenance team.
Power & Energy · Controllers and Sensors — Application Case
Project Background
The project covers boiler feedwater, turbine condensate and FGD/DeNOx systems. The work centres on Controllers and Sensors and the core task is online water monitoring with a controller and sensor combination.
Operating Challenges
The medium and duty are characterised by high temperature and pressure with both steam and saline water, and drift under high temperature and pressure, with very costly unplanned outages. So Controllers and Sensors cannot be specified generically — it calls for matching each controller channel to its sensor type.
Solution
The Ainstru engineering team worked through the Hach channel: supplying against the Hach original part numbers. The configuration involves matching each controller channel to its sensor type, with these requirements in view: compliance with power-industry codes and unit availability targets.
Results
Since start-up the system has run steadily; the practical result is factory-matched combinations that make faults easier to locate.
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