OMRON SRT2 Series Modules

Technical Dossier

Product Details And Specifications

OMRON SRT2 Series: Comprehensive Module Range and Technical Overview

The OMRON SRT2 series, operating under the CompoBus/S (also known as DeviceNet-compatible remote I/O) protocol, represents one of OMRON's most widely deployed distributed I/O platforms in global heavy industry. Installed across petrochemical refineries, nuclear auxiliary systems, chemical processing plants, and continuous manufacturing lines, the SRT2 series functions as a remote slave unit within OMRON's CS/CJ/CV-series PLC architectures. Its compact DIN-rail form factor, deterministic scan cycle, and robust noise immunity made it a standard specification in plant automation projects throughout the 1990s and 2000s. Today, the SRT2 series is in the mature-to-end-of-life phase, with many models discontinued by OMRON. Long-term maintenance support for installed base systems is the primary sourcing driver.

The Evolution of SRT2 Architecture

The SRT2 series was introduced as a successor to the SRT1 platform, addressing limitations in I/O point density and communication reliability. Early SRT1 units supported only 8-point I/O blocks with limited noise rejection on long cable runs. The SRT2 generation introduced 16-point and mixed I/O configurations, improved terminal block designs, and enhanced CompoBus/S compliance at baud rates up to 750 kbps over distances up to 200 meters (in high-speed mode) or 500 meters (in long-distance mode).

Architecturally, SRT2 units are passive slaves — they carry no onboard CPU and rely entirely on the master unit (typically a CS1W-SRM21 or CJ1W-SRM21 CompoBus/S master) for scan cycle management. This design simplifies replacement logistics: any SRT2 slave can be swapped without software reconfiguration, provided the node address DIP switch settings are preserved. Compatibility with OMRON's CX-Programmer and CX-Integrator toolchains remains intact for diagnostic purposes, though firmware updates are not applicable to these passive units.

As OMRON transitioned its remote I/O strategy toward EtherNet/IP and EtherCAT platforms (GRT1, NX-series), the SRT2 series entered a formal end-of-life trajectory. Replacement migration paths include the OMRON GRT1 series (CompoNet) and NX-ECC series (EtherCAT coupler), though these require master unit replacement and network reconfiguration — making in-kind SRT2 spare parts the preferred solution for brownfield maintenance.

SRT2 Full Catalog & Functionalities (SKU List)

The following SKUs represent the verified SRT2 series module range, classified by function. Each model is a discrete remote I/O slave unit for CompoBus/S networks.

Output Modules (Transistor)

• SRT2-MD16T-1: 16-point NPN transistor output slave, 24 VDC, 0.5 A/point, screw terminal
• SRT2-MD16T: 16-point NPN transistor output slave, 24 VDC, standard screw terminal variant
• SRT2-MD08T: 8-point NPN transistor output slave, 24 VDC, compact form factor
• SRT2-MD16TP: 16-point PNP transistor output slave, 24 VDC, positive-common wiring

Input Modules (DC)

• SRT2-ID16: 16-point DC input slave, 24 VDC, NPN/PNP compatible, screw terminal
• SRT2-ID08: 8-point DC input slave, 24 VDC, compact DIN-rail mount
• SRT2-ID16-1: 16-point DC input slave, revised terminal layout, 24 VDC
• SRT2-ID08-1: 8-point DC input slave, revised terminal layout variant

Mixed I/O Modules

• SRT2-MD16D: 8-point input / 8-point output mixed slave, 24 VDC DC I/O
• SRT2-MD08D: 4-point input / 4-point output mixed slave, compact mixed I/O

Relay Output Modules

• SRT2-ROC08: 8-point relay output slave, 250 VAC / 24 VDC, 2 A/point, screw terminal
• SRT2-ROC16: 16-point relay output slave, 250 VAC / 24 VDC contact output

Analog Modules

• SRT2-AD04: 4-channel analog input slave, 0–10 V / 4–20 mA selectable, 12-bit resolution
• SRT2-DA02: 2-channel analog output slave, 0–10 V / 4–20 mA, 12-bit resolution

Special Function / Communication

• SRT2-ID16S: 16-point DC input slave with short-circuit protection per point
• SRT2-MD16T-1S: 16-point NPN transistor output with per-point overcurrent detection

Sourcing Hard-to-Find & Obsolete SRT2 Parts

The SRT2 series has been formally discontinued by OMRON across most regional markets. Standard distribution channels no longer carry new stock for the majority of SRT2 models, including the SRT2-MD16T-1. DriveKNMS maintains a dedicated inventory of SRT2 series units sourced through verified industrial surplus channels, decommissioned plant equipment, and authorized secondary market suppliers.

For end-users operating legacy CompoBus/S networks, DriveKNMS provides: direct replacement units (tested, with traceability documentation), exchange programs for core return, and long-lead procurement for low-volume models. All units are supplied with a functional test report. Minimum order quantities are not imposed for SRT2 spare parts — single-unit orders are accepted to support emergency maintenance scenarios.

Quality Control for the SRT2 Range

SRT2 modules present specific test challenges due to their passive slave architecture and CompoBus/S bus dependency. DriveKNMS applies the following test protocol to all SRT2 units prior to dispatch:

• Node address verification: DIP switch positions are confirmed and documented against the unit's labeled configuration.
• CompoBus/S live network test: Each unit is connected to a CS1W-SRM21 master in a controlled test bench environment. Cyclic I/O data exchange is verified at both 750 kbps (high-speed) and 93.75 kbps (long-distance) baud rates.
• Point-by-point I/O functional test: For output modules (including SRT2-MD16T-1), all 16 transistor outputs are individually energized and load-tested at rated current (0.5 A). For input modules, all input points are stimulated and confirmed in the master's I/O table.
• Terminal block inspection: Screw torque, contact integrity, and corrosion status are assessed. Damaged terminals are replaced before dispatch.
• Insulation resistance check: Applied between I/O terminals and chassis ground per IEC 61131-2 requirements.
• Visual and mechanical inspection: PCB condition, connector integrity, DIN-rail clip function, and label legibility are documented.