HH5400i Four-Electrode Digital Conductivity Sensor| Four-Electrode Graphite Digital Conductivity Sensor

The HH5400i is a digital four-electrode conductivity sensor with its signal conditioning, temperature compensation, and communication electronics integrated into the sensor body. It connects directly to a compatible PLC, controller, data logger, or automation platform using Modbus RTU over an RS485 network.

Four-electrode technology separates the current-carrying and voltage-sensing functions. Compared with a conventional two-electrode design, this arrangement reduces sensitivity to electrode polarization and supports measurement over a broader conductivity range.

The sensor measures conductivity up to 500 mS/cm, equivalent to 500,000 μS/cm. This makes it suitable for applications ranging from general industrial water to seawater and higher-conductivity process liquids. The actual usable lower limit, resolution, and uncertainty at different points across this range must be confirmed before positioning it for low-conductivity water.

An integrated NTC 22K element provides process-temperature data. The standard configuration reports conductivity compensated to 25 °C using a fixed linear coefficient of 2%/°C. This default is commonly useful for general aqueous solutions, but it may not accurately represent seawater, concentrated salts, acids, alkalis, or process mixtures with nonlinear temperature behaviour.

The POM housing incorporates a G3/4 process connection and an integrated cable. Pipeline and immersion configurations are available, together with a low-power option for monitoring systems with restricted energy budgets.

Key benefits

• Integrated digital electronics: No separate conductivity transmitter is required when the receiving system can power and communicate with the sensor directly.
• Four-electrode measurement: Reduces polarization effects and supports a broad conductivity range.
• Direct automation integration: Modbus RTU communication allows connection to compatible PLCs, controllers, gateways, and data-acquisition systems.
• Wide power input: Operates from a 6–30 VDC supply.
• Process installation options: Available for compatible pipeline and immersion assemblies.
• Long-distance digital communication: Cable lengths up to 100 metres are available when network design and power requirements permit.
• Integrated temperature compensation: Conductivity and temperature can be processed within the sensor.

Configuration options

• Low-power version: Available for battery-powered or energy-constrained monitoring systems.
• Installation configuration: Pipeline and immersion versions are available.
• Extended cable: Cable lengths up to 100 metres, subject to power-supply voltage drop and RS485 network design.
• Communication settings: Device address, baud rate, parity, register map, and byte order should be configured for the receiving system.
• Process adapter: Confirm the thread standard, sealing method, and immersion requirements before ordering.

Communication and installation notes

An integrated transmitter removes the need for a separate conductivity signal converter, but the installation still requires a suitable DC power supply and a Modbus-compatible controller, gateway, display, or PLC.

For long RS485 networks, use suitable twisted-pair shielded cable, daisy-chain topology, correct polarity, appropriate termination and biasing, and unique device addresses. Confirm whether the sensor interface is galvanically isolated before connecting it to a grounded process-control network.

The fixed 2%/°C compensation coefficient should only be used when appropriate for the sample. For concentrated salts, seawater, acids, alkalis, or mixtures, use raw conductivity and temperature data with a validated process-specific compensation model if the sensor protocol supports it.

POM, the electrode material, seals, cable jacket, and process connection must all be compatible with the complete chemical composition. General statements such as “acid- and alkali-resistant” should not be interpreted as universal compatibility with every concentration and temperature.

At high conductivity, verify measurement linearity and temperature behaviour. At low conductivity, verify the minimum measuring value and resolution because a maximum range of 500 mS/cm does not establish high-purity-water performance.

Classification

Product Type

• Industrial Sensors

Parameter

• Conductivity
• Temperature

Connectivity

• Digital
• RS485
• Modbus RTU

Application

• Industrial Wastewater Treatment
• Seawater & Brackish Water
• Industrial Process Water
• Concentrated Salt Solutions
• Compatible Acid & Alkali Processes
• Chemical Processing
• OEM Monitoring & Automation Systems
• Remote Water-Quality Monitoring