OMRON SRT2 Series Modules SRT2-VOD16ML-1

Technical Dossier

Product Details And Specifications

OMRON SRT2 Series Technical Notes

The OMRON SRT2 series is a compact, high-density remote I/O slave unit family designed for the CompoBus/S (also known as CompoNet predecessor) fieldbus network. Deployed extensively across global heavy industry — including petrochemical plants, nuclear facility auxiliary systems, refinery distributed control architectures, and automotive assembly lines — the SRT2 series established OMRON's position as a dominant supplier of distributed I/O in Asia-Pacific and European process automation markets throughout the 1990s and 2000s. Its terminal-block form factor, DIN-rail mounting, and deterministic cycle time made it a preferred choice for machine builders requiring reliable, high-node-count I/O expansion without the overhead of full PLC backplane systems.

The Evolution of SRT2 Architecture

The SRT2 series was introduced as a successor to the SRT1 slave units, addressing limitations in node density and wiring flexibility. Early SRT1 units required dedicated cabling and offered limited I/O point counts per node. The SRT2 generation introduced terminal-block connectivity (ML-1 suffix variants), enabling direct field wiring without intermediate terminal strips — a significant reduction in panel wiring labor. The series operates on the CompoBus/S protocol, a OMRON-proprietary high-speed serial bus capable of connecting up to 32 slave nodes with a maximum of 256 I/O points at cycle times as low as 0.5 ms.

As industrial networks migrated toward open standards (DeviceNet, EtherNet/IP, PROFIBUS), the SRT2 series entered a maintenance phase. OMRON officially transitioned customers toward the GRT1 (CompoNet) and NX-series I/O platforms. However, the installed base of SRT2 units in legacy systems remains substantial, and replacement demand for end-of-life units continues across MRO (Maintenance, Repair & Operations) channels. Compatibility between SRT2 slaves and CS/CJ-series PLC masters via SRM1 or C200HW-SRM21-V1 master units remains fully supported at the protocol level.

SRT2 Full Catalog & Functionalities (SKU List)

The following SKUs represent the verified SRT2 series module range, classified by function. Each unit is a CompoBus/S slave device.

Digital Output Modules (Transistor)

SRT2-VOD16ML-1: 16-pt NPN transistor output, terminal block, 24 VDC, CompoBus/S slave
SRT2-VOD08ML-1: 8-pt NPN transistor output, terminal block, 24 VDC, CompoBus/S slave
SRT2-VOD16A: 16-pt NPN transistor output, connector type, 24 VDC, CompoBus/S slave
SRT2-VOD08A: 8-pt NPN transistor output, connector type, 24 VDC, CompoBus/S slave
SRT2-VOD16PML-1: 16-pt PNP transistor output, terminal block, 24 VDC, CompoBus/S slave
SRT2-VOD08PML-1: 8-pt PNP transistor output, terminal block, 24 VDC, CompoBus/S slave

Digital Input Modules

SRT2-VID16ML-1: 16-pt DC input, terminal block, 24 VDC, CompoBus/S slave
SRT2-VID08ML-1: 8-pt DC input, terminal block, 24 VDC, CompoBus/S slave
SRT2-VID16A: 16-pt DC input, connector type, 24 VDC, CompoBus/S slave
SRT2-VID08A: 8-pt DC input, connector type, 24 VDC, CompoBus/S slave

Mixed I/O Modules

SRT2-MD16ML-1: 8-pt input / 8-pt NPN output, terminal block, 24 VDC, CompoBus/S slave
SRT2-MD08ML-1: 4-pt input / 4-pt NPN output, terminal block, 24 VDC, CompoBus/S slave
SRT2-MD16A: 8-pt input / 8-pt NPN output, connector type, 24 VDC, CompoBus/S slave

Relay Output Modules

SRT2-ROC08ML-1: 8-pt relay output, terminal block, 250 VAC / 24 VDC, CompoBus/S slave
SRT2-ROC16ML-1: 16-pt relay output, terminal block, 250 VAC / 24 VDC, CompoBus/S slave

Analog Modules

SRT2-AD04: 4-ch analog input, 0–10 V / 4–20 mA selectable, CompoBus/S slave
SRT2-DA02: 2-ch analog output, 0–10 V / 4–20 mA selectable, CompoBus/S slave

Quality Control for the SRT2 Range

SRT2 modules present specific test challenges due to their integrated terminal block assemblies and CompoBus/S ASIC-based communication logic. DriveKNMS applies the following verification protocol to all SRT2 units prior to dispatch:

1. Visual inspection: terminal block integrity, PCB corrosion, capacitor condition, connector pin alignment.
2. Power-on test: 24 VDC supply applied, LED status indicators verified against OMRON factory specification.
3. Functional I/O test: each output channel individually energized and confirmed via load simulation; each input channel verified with signal injection.
4. CompoBus/S communication test: unit connected to a live SRM1 master network, node address assigned, cyclic data exchange confirmed at rated cycle time.
5. Burn-in: 4-hour continuous operation under load prior to packaging.