Overview
The Eurotherm 818S RTD is a 1/4 DIN format temperature controller combining RTD input compatibility, analog 4-20mA output, and digital RS485 Modbus communication for flexible process control applications. This surplus unit is fully functional and ideal for retrofit, replacement, or OEM integration in industrial heating, cooling, and process automation systems requiring precise temperature regulation from 0–400°C.
Key Features
- RTD Input Module — R4MA20 module supports resistance temperature detector measurement with high accuracy and repeatability
- Single-Loop PID Control — Delivers stable, responsive closed-loop temperature management without programmable profiles
- RS485 Modbus Serial Communication — 9600 baud digital interface for remote monitoring, setpoint adjustment, and system integration
- Isolated 4-20mA Output — Proportional analog output for valve positioning, variable frequency drives, or process recorder integration
- 96×96 Display — Clear 7-segment readout for process value, setpoint, and status indication
- Compact 1/4 DIN Footprint — Mounts directly in standard panel cutouts; screw terminal connections
Technical Specifications
| Display Format | 96×96 mm (1/4 DIN) |
| Input Type | RTD (Pt100/Pt1000 compatible) |
| Input Module | R4MA20 |
| Temperature Range | 0–400°C (factory configured) |
| Display Range | 0–400°C |
| Output 1 | 4-20mA, Isolated, 24 VDC excitation |
| Output 2 | None |
| Communication | RS485 Modbus (9600 baud) |
| Alarm Functions | None (this configuration) |
| Digital Inputs | None |
| Connectors | Screw terminals |
| Control Logic | Standard (non-programmable single-loop) |
| Accuracy | ±50 ppm/°C of instrument input span (typical) |
Typical Applications
- Plastic & Injection Molding — Temperature control of barrel heaters, nozzles, and molds
- Thermal Processing — Ovens, furnaces, and curing chambers
- Semiconductor & Laboratory — Precision heating and cooling of test chambers and process equipment
- Food & Beverage — Pasteurization, sterilization, and process heat control
- Fluid Heat Exchange — Water heater control, thermal loop regulation, and heat recovery systems
Compatibility & Replacements
Compatible With
- Standard RTD sensors (Pt100, Pt1000 types)
- RS485 / Modbus industrial networks and SCADA systems
- Analog control loops requiring 4-20mA feedback or demand signal
- 24 VDC auxiliary power supplies
- Standard 1/4 DIN panel cutouts (96×96 mm)
Replaces / Drop-In Replacement For
- Eurotherm 818S RTD configurations with identical I/O and communication specifications
- Other 1/4 DIN single-loop RTD controllers requiring RS485 Modbus and 4-20mA output
Works With
- Modbus RTU protocol (slave mode)
- Scada systems with RS485 serial support
- Proportional valve actuators and VFD control loops
- Process recorders accepting 4-20mA input
- Industrial automation platforms supporting Modbus serial
