NEX252, NEX255 - Universal Process Controller with Dual Inputs, Analog Outputs, Alarms & Modbus RTU

The Radix NEX252 and NEX255 process controllers are high-performance Universal Process Controllers designed for industrial process automation and control applications. They support up to two universal inputs for Thermocouples, RTDs, mA, mV, and Voltage signals, along with up to two isolated analog outputs, four relay outputs for alarm or ON/OFF control, and RS485 Modbus RTU communication.

The NEX252 and NEX255 combine process measurement, control, alarm monitoring, analog signal output, and digital communication in a compact panel-mounted controller. The controllers feature two 5-digit, 7-segment LED displays for clear process value and setpoint indication, while programmable parameters provide flexibility for different process control requirements.

These industrial process controllers are suitable for interfacing field sensors with PLCs, SCADA systems, DCS systems, data acquisition systems, and other industrial control equipment. With programmable alarm functions, isolated analog outputs, RS485 Modbus RTU communication, and mutual electrical isolation between input, supply, relays, analog output, digital input, and RS485, the NEX252 and NEX255 provide a flexible solution for industrial process measurement and control.

The controllers support ON/OFF control and programmable alarm functions for a range of process control applications. For level measurement applications, a 256-point volume strap function is also available in the level controller to enable volume display in non-linear tanks.

Working Principle of NEX252, NEX255 Process Controller

The NEX252/NEX255 receives process signals from industrial sensors such as Thermocouples, RTDs, Current, voltage, and mV sources through its universal inputs. The controller measures and processes the incoming signal according to the configured input type, range, resolution, and control parameters.

The controllers support two inputs, Input 1 and Input 2. Depending on the selected input group and configuration, the supported inputs include multiple Thermocouple types, RTDs, current, voltage, mV and RS485 input received from an RS485 Modbus RTU master.

The measured process values are displayed on the 5-digit LED displays, while the controller can operate relay outputs for alarm or ON/OFF control and provide isolated analog outputs for retransmission of process signals.

The controller also supports RS485 Modbus RTU communication, allowing process values and controller parameters to be communicated with compatible PLCs, SCADA systems, DCS systems and other industrial automation equipment.

Programmable functions include alarm logic, alarm delay, alarm acknowledgement, relay action, digital input functions, power-on delay, soft start, digital filtering and ramp/soak control, providing flexibility for different process applications.

Why Choose NEX252, NEX255?

Unlike basic process indicators that only display a measured process value, the NEX252 and NEX255 combine process measurement, alarm/control outputs, analog retransmission and digital communication in one industrial controller.

The NEX252 and NEX255 provide flexible input, output, and communication options for industrial process measurement and control applications.

Key advantages include:

Up to two universal process inputs
Supports Thermocouple inputs
Supports Pt100, Cu53 and JPT100 RTD inputs
Supports 4-20 mA and 0-20 mA current inputs
Supports voltage and mV inputs
Supports 4-20 mA input with square-root function
Up to four relay outputs for alarm / ON-OFF control
Up to two isolated analog outputs
4-20 mA, 0-20 mA, 20-4 mA and 20-0 mA analog output options
0-10 V or user-specified voltage output
RS485 Modbus RTU communication
User-programmable Modbus slave ID from 1-247
Two 5-digit, 7-segment LED displays
Programmable alarm types
Programmable alarm delay
Programmable alarm acknowledgement
User-selectable input resolution
Automatic or programmable cold junction compensation
Programmable sensor break protection
Digital filter function
Programmable sampling time of 50 ms / 200 ms
Transmitter supply of 22 V nominal, 30 mA maximum
Ramp/soak function
Soft start function
Power-on delay
Standard 35 mm DIN Rail is not applicable; panel mounting is provided
Panel-mounted compact design
Front IP66 / approximately NEMA 4X protection
Available in NEX252 and NEX255 panel-mount formats
NEX255 also available in flameproof configuration

Applications

The NEX252 and NEX255 are widely used wherever process variables must be measured, displayed, controlled, alarmed, or communicated to other automation systems.

Typical applications include:

Process Automation
Temperature Control
Pressure Monitoring
Flow Monitoring
Level Monitoring
Boiler Control
Furnace Automation
Industrial Process Control
Chemical Plants
Pharmaceutical Manufacturing
Food & Beverage Industry
Water & Wastewater Treatment
HVAC Systems
Power Plants
Cement Plants
Steel Industry
Oil & Gas
OEM Control Panels
Industrial Data Acquisition
PLC & SCADA Integration
DCS Integration
Machine Automation
Utility Monitoring

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