NEX255 - Dual Universal Input Level (and Process) Controller with Volume Strapping, Alarms & Modbus RTU

The Radix NEX255 is a versatile Dual Universal Input Level & Process Controller designed for industrial level measurement, tank volume calculation, process monitoring and control applications. It provides two universal inputs for commonly used industrial signals including 4-20 mA, 0-20 mA and 0-10 V, allowing the controller to interface with a wide range of level transmitters and process sensors.

The NEX255 provides up to 256 volume-strap points for each level input, enabling accurate volume calculation for tanks and vessels with non-linear shapes. The level-to-volume relationship can be configured through the controller keys or conveniently using Radix PC Configuration Software. The software supports Excel-based volume-strapping configuration, allowing users to prepare and enter the complete set of level-to-volume points through an Excel sheet.

With its two universal inputs, the NEX255 can also be used as a general-purpose Process Controller for applications involving flow, temperature, pressure, differential pressure and level. Two independent process variables can be monitored using a single controller, making it suitable for OEM equipment, process skids and industrial automation applications.

The NEX255 provides up to four programmable relay outputs, two isolated analog outputs and isolated RS485 Modbus RTU communication. The relay outputs can be used for alarms and ON/OFF control, while analog outputs can be used for signal retransmission or control. The Modbus RTU interface enables integration with PLCs, SCADA systems, BMS, HMIs and other industrial automation systems.

Working Principle of NEX255 Level Controller

For level control applications, the NEX255 receives level signals from one or two field transmitters through its universal inputs. Supported signals include 4-20 mA, 0-20 mA and 0-10 V, allowing the controller to measure the level of the connected tanks.

The measured level is converted into the corresponding tank volume using a configured 256-point volume-strapping table. This allows the NEX255 to provide accurate volume indication even when the relationship between tank level and volume is non-linear.

The volume-strapping data can be configured directly through the controller keys or through Radix PC Configuration Software. The software provides an Excel-based method for entering level-to-volume data, making it convenient to configure multiple strap points during commissioning.

The calculated volume can be displayed by the controller, while programmable relay outputs can be used for high/low level alarms and other configured alarm functions. Analog outputs can be used for isolated signal retransmission, and the RS485 Modbus RTU interface allows level and volume data to be integrated with PLCs, HMIs, SCADA systems and other automation systems.

Working Principle of NEX255 Process Controller

For process control applications, the NEX255 uses its two universal inputs to measure different process variables. The inputs can be configured for signals such as Thermocouples, RTD, mV, 4-20 mA, 0-20 mA and 0-10 V, allowing the controller to be used for applications involving flow, temperature, pressure, differential pressure and other process parameters.

The measured process values can be monitored through the controller display and used for alarm and control functions. Depending on the application, programmable relay outputs can be used for process alarms and ON/OFF control, while analog outputs can be used for isolated process signal retransmission or control.

The NEX255 also supports RS485 Modbus RTU communication, allowing process values and other relevant parameters to be integrated with PLCs, HMIs, SCADA systems and industrial automation networks.

Why Choose NEX255?

NEX255 works as a Dual Channel Level Controller, with Volume Strapping function for each channel. Additionally, the same product can be used as a Dual Channel Process Controller for temperature, pressure, flow and other applications. This reduces the inventory to be maintained in process plants significantly.

As a level controller, NEX255 combines level measurement, volume calculation, process monitoring, alarms, control, analog retransmission and Modbus communication in one flexible controller.

As a Process Controller, NEX255 shares its lineage with the industry standard PID Process Controller NEX205, and has all the functions of NEX205, in addition to the increased 5-digit resolution.

Key advantages include:

Dual universal process inputs
Suitable for level and general process measurement (temperature, pressure, flow, humidity, etc)
Supports 4-20 mA, 0-20 mA and 0-10 V inputs
Up to 256 volume-strapping points for each level input
Accurate volume calculation for non-linear tanks
Volume-strapping configuration through front-panel keys
Radix PC Configuration Software
Excel-based volume-strapping configuration
Excel-based level-to-volume data entry
Up to four programmable relay outputs
Up to two isolated analog outputs
Programmable process alarms
High and low level alarms
ON/OFF control
RS485 Modbus RTU communication
PLC and SCADA integration
BMS integration
Suitable for flow measurement and monitoring
Suitable for temperature measurement and control
Suitable for pressure monitoring and control
Suitable for differential pressure monitoring
Two-parameter process monitoring
Programmable alarm delay
Alarm acknowledgement through user key or digital input
Programmable digital filtering
Programmable sampling time
Transmitter excitation supply
Electrical isolation between input, supply, relays, analog output, digital input and RS485
Compact panel-mounted industrial design
Suitable for OEM and industrial automation applications

Flexible Volume-Strapping Configuration

The NEX255 provides 256 volume-strapping points for each level input, making it suitable for tanks and vessels with irregular or non-linear geometry.

Each strap point defines the relationship between the measured level and the corresponding tank volume. This allows the controller to provide a more accurate volume indication than a simple linear level-to-volume conversion.

For convenient commissioning, the volume-strapping data can be configured using Radix PC Configuration Software. Users can prepare the level and corresponding volume values in an Excel sheet and enter the complete volume-strapping table into the controller through the software

This provides a convenient solution for applications involving:

Large storage tanks
Non-linear tanks
Irregular-shaped vessels
Process tanks
Chemical storage tanks
Water storage tanks
Fuel and oil storage tanks
OEM tank systems

One Controller – Multiple Process Applications

The NEX255 is not limited to level measurement. Its two universal inputs allow it to be configured for a wide range of process measurement and control applications.

Depending on the input and output configuration, the NEX255 can be used as a:

Level Controller
Tank Volume Controller
Flow Controller
Temperature Controller
Pressure Controller
Differential Pressure Controller
General-Purpose Process Controller

The two inputs can also be used for simultaneous monitoring of two independent process variables, such as:

Temperature + Flow
Temperature + Pressure
Level + Temperature
Level + Flow
Pressure + Flow
Differential Pressure + Temperature

Applications

The NEX255 is suitable for a wide range of level and industrial process measurement and control applications.

Typical applications include:

Tank Level Measurement
Tank Level Monitoring
Tank Volume Measurement
Liquid Level Control
Water Level Monitoring
High-Level / Low-Level Alarm
Tank Overfill Monitoring
Pump ON/OFF Control
Flow Measurement & Monitoring
Flow Control
Temperature Measurement & Control
Pressure Monitoring & Control
Differential Pressure Monitoring
Process Tank Monitoring
Storage Tank Monitoring
Water & Wastewater Treatment
HVAC Process Monitoring
Process Skid Monitoring
Industrial Process Automation
PLC & SCADA Integration
Remote Tank Monitoring
Industrial Data Acquisition

Industries

The NEX255 can be used across industries where level, volume or process parameters need to be measured, monitored and controlled.

Typical industries include:

Water & Wastewater Treatment
Chemical Industry
Pharmaceutical Industry
Food & Beverage Industry
Oil & Gas
Petrochemical Industry
Power Plants
Manufacturing
Process Industries
HVAC
Industrial Utilities
ETP / STP Plants
OEM Equipment
Process Skids
Tank Farms
Storage Facilities

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