OMRON SRT2 Series Modules: SRT2-VOD16ML-1

Technical Dossier

Product Details And Specifications

OMRON SRT2 Series: Comprehensive Module Range and Technical Overview

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

Sourcing Hard-to-Find & Obsolete SRT2 Parts

The SRT2 series has been officially discontinued by OMRON. Standard distribution channels no longer carry new stock for the majority of SRT2 variants, including the SRT2-VOD16ML-1. DriveKNMS maintains a dedicated inventory of tested surplus and refurbished SRT2 modules sourced from decommissioned plant equipment, controlled warehouse stock, and verified secondary market channels.

For facilities operating legacy CompoBus/S networks where a full migration to CompoNet or EtherNet/IP is not economically viable in the short term, DriveKNMS provides lifecycle extension support: single-unit replacement, multi-unit lot procurement, and cross-reference identification for units where the original label is damaged or illegible. Lead times for common SRT2 variants are typically 3–10 business days from confirmed order.

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.

Units that fail any stage are quarantined and not offered for sale. Test records are retained and available upon request for critical infrastructure procurement.