WL-CON-3661 Industrial Conductivity Meter

The WL-CON-3661 is an industrial conductivity meter designed for continuous online water-quality monitoring and process control. It receives signals from a compatible two-electrode conductivity sensor, calculates conductivity or resistivity, measures temperature, and transfers the results to plant monitoring and control systems.

The meter can be paired with sensors having cell constants of 0.01, 0.10, 1.00, or 10.0 cm⁻¹. This allows the same instrument platform to support applications ranging from pure and demineralized water to tap water, process water, and compatible higher-conductivity industrial solutions.

Automatic range switching, selectable measurement frequencies, software-based zero correction, configurable temperature compensation, and digital signal processing help maintain stable measurements under changing process conditions.

Two isolated 4–20 mA outputs, high and low alarm relays, and RS485 communication using the Modbus RTU protocol allow the WL-CON-3661 to be integrated into compatible PLC, SCADA, dosing, and process-control systems.

Measurement and Control Functions

Multiple Conductivity Ranges

The selected conductivity sensor determines the available measurement range. Choosing the correct cell constant helps ensure that the normal process value remains within the sensor’s effective working range.

These application directions are general selection guidance. Final sensor selection should be based on the expected normal value, maximum conductivity, process composition, temperature, pressure, and transmitter compatibility.

Automatic Range Switching

Within the configured sensor range, the meter automatically selects an appropriate display range according to the measured conductivity. This allows low and high readings to be displayed clearly without repeated manual range adjustment.

Configurable Temperature Compensation

Conductivity changes significantly with temperature. The WL-CON-3661 uses the connected temperature sensor to compensate the measured conductivity to the selected reference condition.

For pure-water applications, the instrument provides a dedicated compensation mode combining two temperature-coefficient models. For other aqueous solutions, the temperature coefficient can be configured according to the process requirements.

Temperature compensation must match the actual sample chemistry. Pure water, neutral salts, acids, alkalis, and mixed industrial water do not share one universal temperature coefficient.

Selectable Measurement Frequency

Three measurement frequencies can be selected according to the conductivity of the process solution. Selecting an appropriate frequency helps control electrode polarization and electrical-capacitance effects across different conductivity ranges.

Analog and Digital Communication

The WL-CON-3661 provides two configurable isolated 4–20 mA outputs for connection to compatible recorders, PLCs, dosing systems, and control equipment.

RS485 communication with the standard Modbus RTU protocol enables remote access to measurement data and instrument parameters.

Alarm and System Protection

Users can configure upper and lower conductivity alarm limits. Alarm conditions are shown on the display and can activate the corresponding relay contacts.

An integrated watchdog monitors program operation and helps the instrument recover from abnormal software conditions. Configuration and calibration parameters are stored in non-volatile memory and remain available after a power interruption without requiring a backup battery.

Typical Applications

The WL-CON-3661 is suitable for continuous conductivity monitoring in the following applications:

• Pure and demineralized water systems
• Reverse-osmosis permeate monitoring
• Industrial water-treatment systems
• Municipal and tap-water monitoring
• Surface-water monitoring
• Recirculating and cooling-water systems
• Electronics and semiconductor water treatment
• Pharmaceutical water-treatment processes
• Chemical manufacturing
• Food and beverage production
• Pulp and paper manufacturing
• Power-generation water systems
• OEM water-treatment and automation equipment

Suitable Operating Environments

Control Panel Installation

The WL-CON-3661 is intended for installation in an indoor control panel or instrument cabinet where:

• Ambient temperature remains between 0 and 45 °C
• Relative humidity does not exceed 90%
• Condensation is prevented
• The meter is protected from direct water spray
• Excessive dust and vibration are controlled
• Corrosive gases do not enter the instrument enclosure
• A stable 220 VAC power supply is available
• Adequate space is provided for wiring, ventilation, and maintenance

No enclosure protection rating has been provided for the panel meter. Outdoor, washdown, or exposed installations require a suitably rated protective cabinet.

Process Measurement Conditions

The connected sensor and process assembly should be selected for:

• Process-liquid temperatures from 5 to 60 °C
• Process pressures not exceeding 0.3 MPa
• The expected conductivity range
• The chemical composition of the sample
• The required pipeline, flow-through, or immersion installation
• The applicable electrode, insulator, seal, and cable materials
• The required flow rate and minimum immersion depth

The process temperature and pressure limits apply to the selected conductivity sensor and installation assembly, not only to the panel-mounted meter.

Installation and Measurement Considerations

Select the Correct Cell Constant

Do not select a sensor only according to the maximum published range. Choose a cell constant that places the normal process conductivity comfortably within the effective measurement range.

A cell constant that is too low may be unsuitable for higher-conductivity liquids. A cell constant that is too high may reduce measurement sensitivity in pure or low-conductivity water.

The sensor cell constant entered in the meter must match the actual sensor.

Match Temperature Compensation to the Sample

A single linear temperature coefficient is not suitable for every liquid. Use a compensation mode appropriate for the process:

• Pure-water compensation for compatible low-conductivity water
• Neutral-salt compensation for suitable general water samples
• Process-specific coefficients for acids, alkalis, salts, or other defined solutions

Incorrect compensation can produce a stable but inaccurate conductivity value.

Control Low-Conductivity Water Conditions

Pure and low-conductivity water is particularly sensitive to contamination and sampling conditions. For reliable measurement:

• Use a clean, closed flow-through system where practical
• Maintain stable sample flow and temperature
• Prevent air ingress and trapped bubbles
• Minimize atmospheric carbon-dioxide absorption
• Avoid stagnant sample lines
• Use clean, compatible tubing and fittings
• Prevent contamination from upstream sensors and reference electrodes

For a combined conductivity and pH sampling line, position the conductivity sensor upstream of the pH electrode where practical. Electrolyte leaking from a pH reference junction can contaminate low-conductivity water.

Avoid Air Bubbles and Incomplete Immersion

The sensor electrodes must remain correctly immersed. Air bubbles, insufficient water level, or partially exposed electrodes can change the effective cell geometry and cause low, unstable, or non-representative readings.

Install the sensor where bubbles can escape and the sample remains representative.

Prevent Electrical Interference

Route sensor cables separately from power lines, motors, frequency converters, relay wiring, and other sources of electromagnetic interference.

Avoid unnecessary cable extension. Long cables increase electrical capacitance and may affect low-conductivity measurements, even when the installation remains within the stated 100 m maximum.

Inspect and Clean the Sensor

Deposits on the conductivity sensor change its effective cell constant:

• Non-conductive scale or coatings may reduce the measured value
• Conductive particles or metal deposits may increase the measured value
• Oil, biofilm, suspended solids, and corrosion products may cause drift or slow response

Cleaning methods must be compatible with the electrode material, insulator, seals, and process chemicals.

Verify Calibration Under Representative Conditions

Confirm the correct sensor cell constant and temperature reading before adjusting the meter. Calibration should use an appropriate conductivity standard or a verified reference method.

A successful laboratory calibration does not automatically confirm accuracy under actual online flow, temperature, pressure, contamination, and electrical conditions.

Required System Components

The WL-CON-3661 is a panel-mounted meter and does not contact the process liquid directly. A complete measurement system normally requires:

• A compatible conductivity sensor
• The correct sensor cell constant
• A compatible temperature element
• Sensor cable and wiring
• A process holder or flow-through chamber
• Suitable seals and process fittings
• A representative sample flow
• Connection to the plant power and control system