Spirax Sarco Spirax Sarco SX25 Process Controller

The Spirax Sarco SX25 process controller is a highly accurate 1/16 DIN panel mounted controller from leading UK steam systems brand Spirax Sarco, designed for constant set point applications and for seamless use with pneumatic (PN) and electric (EL) control valves and sensors. Suitable for temperature and pressure process control of steam, water, or other industrial fluids, the controllers offer advanced PID algorithms, adaptive tuning, and auto-tuning to ensure stable system operation and precise control.The SX25 series, including the SX25 mA (a linear mA output model) and the SX25 VMD (a valve motor-driven model), provides highly efficient process optimization without the need for complex external configurations. They are widely used in industrial heating, cooling and steam management systems. With its IP65 protection and EMC design, it excels in harsh environments, helping users to reduce energy consumption and increase productivity.

Product Features

• Advanced control algorithmsPID control is supported with proportional band 0.5-999.9%, integral time 0.1-100.0 minutes (or off), differential time 0.01-10.00 minutes (or off), and error band 0.1-10%. The On-Off control band has a hysteresis of 0.1-10% and is equipped with a minimum overshoot function that protects critical processes from fluctuating effects.
• Automatic and adaptive tuning: Single tuning or natural frequency tuning, the controller intelligently selects the best method based on process conditions; adaptive tuning continuously optimizes PID parameters through non-intrusive analysis to improve control accuracy.
• Universal Input SupportCompatible with resistance thermometers (Pt100, 2/3 wire), thermocouples (L, J, T, K, S, or custom), linear mA (4-20mA, 0-20mA), and voltage signals (0/10-50mV), with a sampling time of only 500ms to ensure a real-time response. the SX25 mA models are additionally available with an auxiliary power supply (+18V ±20%, 30mA max) for loop powered sensors. The SX25 mA model is available with an additional auxiliary power supply (+18V ±20%, 30mA max.) for loop powered sensors.
• Flexible Output ConfigurationSX25 mA: Linear mA output (0/4-20mA with 0.1% accuracy) plus multiple relay/SSR outputs (2A/250Vac). SX25 VMD: Dual relay valve drive supporting 15-600 second travel times and 0.1-5.0% minimum steps. Two programmable relays for deviation, bandwidth and process alarms with latching and blocking.
• Operational ConvenienceKeypad switching in auto/manual mode, displaying percentage of power output; supports two independent ramps (rising/falling) for smoothing setpoint changes.IP65 front panel protection, operating temperature 0-50°C, relative humidity 5-90%, suitable for industrial sites.
• Safety and CompatibilityComplies with EN 61010-1 safety standard and EMC directive 89/336/EEC, including RF emission and immunity requirements. ce certification ensures reliability and compliance.

technical specification

• Power Requirements: 100-240Vac, 50/60Hz, maximum power consumption 1.6VA.
• Input Accuracy: RTD/Thermocouple: 0.25% ±1 bit; Linear mA: 1.25% ±1 bit; Voltage: 0.10% ±1 bit (25°C ambient).
• Output details::
  • SX25 mA: mA output resolution 12-bit (0.025%), maximum load 750Ω; relay output SPST normally open 2A/250Vac.
  • SX25 VMD: Valve Driver Relay 2x SPST normally open 2A/250Vac.
• Size and Installation: Panel cutout 45x45mm (+0.6mm), overall 48x48x120mm, weight approx. 130g. screw terminal connection, depth at least 65mm.
• Environmental adaptation: 0-50°C operating temperature for non-explosive environments.

Installation and Maintenance Guide

Ensure panel cutouts are accurate during installation and verify power compatibility before connecting. Electrical wiring is subject to safety regulations to avoid electromagnetic interference. Commissioning is simplified by auto-tuning and no routine maintenance is required, but it is recommended that input signals be checked and PID parameters calibrated periodically. Manual mode allows direct output tuning to test system response. Please refer to the official manual for detailed installation procedures.

Links to related documents

• SX25 Process Controller Technical Information Sheet (PDF) - Includes full specifications and configuration guide.
• SX25 Series Installation and Maintenance Manual - Download the PDF for safety and operational details.