Overview
The Eurotherm 818S RTD temperature controller is a 1/4 DIN, single-loop temperature/process controller designed for precise industrial temperature measurement and control. This used unit features RTD (Resistance Thermometer Device) input capability, 4-20mA analog output, and RS485 digital communications, making it a reliable solution for retrofits, OEM upgrades, or production line expansions. The modular design allows configuration of input types, output functions, and communication protocols to match specific application requirements.
Key Features
- Single-loop PID control with tuning parameters for stable temperature regulation
- RTD input with programmable temperature range (0–400°C in this configuration)
- Isolated 4-20mA analog output for integration with DACs, relays, or proportional valves
- RS485 digital communications at 9600 baud for remote monitoring and setpoint adjustment
- 1/4 DIN panel-mount form factor; compact footprint for tight cabinet spaces
- Screw terminal connections for fast field installation
- Internal cold-junction compensation and manual key enable functionality
Technical Specifications
| Parameter | Value |
| Model | Eurotherm 818S/RTD/R4MA20/CTRI/DHD/DLD/485/96/FN/>70/0/400/C/AM/S2/E/N/S/N/ |
| Product Type | Temperature/Process Controller |
| Input Type | RTD (Resistance Thermometer Device) |
| Input Range | 0–400°C |
| Output 1 | Isolated 4-20mA, Reverse Acting (proportional control) |
| Output 2 | Deviation Band (High/Low alarm output) |
| Communications | RS485 digital at 9600 baud |
| Supply Voltage | 100–240VAC ±10%, 48–62 Hz |
| Power Consumption | Approx. 8.5–10W |
| Control Mode | PID with Integral & Derivative in Seconds |
| Display | 6-button interface with digital readout |
| Mounting | 1/4 DIN panel mount |
| Connections | Screw terminals |
| Weight | Approx. 1.0–1.4 kg |
| Condition | Used, tested, fully functional |
Typical Applications
- Process heating, cooling, and ovens in pharmaceutical, food, and laboratory environments
- Reactor temperature monitoring and control in chemical processing
- Mold temperature regulation in injection molding and extrusion
- Industrial heat-treat furnaces and thermal processing equipment
- HVAC and building automation systems requiring remote temperature setpoint adjustment
- Retrofit installations where analog and digital control integration is required
Compatibility & Replacements
Compatible With
- RTD sensors (Pt100, Pt1000) and resistance thermometer probes
- Proportional solenoid valves, heating elements, and cooling fans (4-20mA actuation)
- SCADA systems and PLCs supporting RS485 Modbus protocol
- Industrial process control software and remote monitoring dashboards
- Eurotherm ToolBox and EasyBuild software for programming and diagnostics
Replaces / Drop-In Replacement For
- Older Eurotherm 818 series controllers with similar module configurations
- Generic 1/4 DIN temperature controllers requiring RTD + 4-20mA output
- Verify exact compatibility with original equipment documentation before replacement
Works With
- RS485 / Modbus digital communications protocol
- 9600 baud serial communication standard
- Eurotherm ToolBox programming software
- Standard industrial SCADA platforms (Ignition, FactoryTalk, Wonderware)
- Any controller or gateway with Modbus RTU slave capability
