OPTO 22 SNAP Series Modules

Technical Dossier

Product Details And Specifications

OPTO 22 SNAP Series: Comprehensive Module Range and Technical Overview

The OPTO 22 SNAP (Simple Networking and Automation Platform) series represents one of the most widely deployed modular I/O architectures in global heavy industry. Installed across petrochemical refineries, nuclear power facilities, chemical processing plants, and offshore platforms, SNAP hardware is recognized for its deterministic signal conditioning, galvanic isolation per channel, and compatibility with both legacy PAMUX and modern Ethernet-based control backbones. The series operates on a rack-and-module architecture where brain boards (processors/communication controllers) mount to a SNAP rack and interface with discrete, analog, and serial I/O modules. This design has made SNAP a standard reference platform for distributed control system (DCS) integrators and plant maintenance engineers requiring long-term parts availability.

The Evolution of SNAP Architecture

The SNAP platform was introduced by OPTO 22 in the mid-1990s as a successor to its G4 and Pamux module families. The first-generation SNAP racks used serial RS-485 brain boards (SNAP-B series) communicating via OPTO 22's proprietary OptoMMP protocol. By the early 2000s, OPTO 22 introduced Ethernet-based brain boards (SNAP-ENET series), enabling direct TCP/IP integration without a dedicated controller. The SNAP-PAC architecture followed, adding onboard IEC 61131-3 logic execution, peer-to-peer communication, and integration with OPTO 22's PAC Control and PAC Display software suites.

Compatibility across generations is a critical maintenance consideration: older SNAP-B brain boards are not pin-compatible with SNAP-ENET or SNAP-PAC brains, though the I/O modules themselves (analog, digital, serial) are physically interchangeable across all rack generations. Plants running first-generation SNAP racks must source original SNAP-B or SNAP-ENET-S brain boards, which are now discontinued. DriveKNMS maintains inventory of these legacy components to support lifecycle extension programs.

SNAP Full Catalog & Functionalities (SKU List)

Analog Input Modules

• SNAP-AIV-8: 8-channel ±10 VDC analog voltage input module, 12-bit resolution, 200 kHz aggregate throughput
• SNAP-AIV: Single-channel ±10 VDC analog voltage input, legacy single-channel format for high-density racks
• SNAP-AIMA: 4–20 mA current loop input, single channel, loop-powered, HART-transparent
• SNAP-AIMA-8: 8-channel 4–20 mA current input module, simultaneous sampling, 16-bit resolution
• SNAP-AITM: Thermocouple input module, supports J, K, T, E, R, S, B types, cold-junction compensated
• SNAP-AITM-8: 8-channel thermocouple input, multi-type configurable per channel, 24-bit ADC
• SNAP-AIRTD: RTD input module, supports PT100/PT1000, 3-wire and 4-wire configurations
• SNAP-AIRTD-8: 8-channel RTD input, 24-bit resolution, supports PT100, PT500, PT1000

Analog Output Modules

• SNAP-AOV-25: ±10 VDC analog voltage output, 16-bit resolution, 25 mA drive capability
• SNAP-AOMA: 4–20 mA current output, single channel, 600Ω max load, short-circuit protected
• SNAP-AOMA-8: 8-channel 4–20 mA current output, independent channel control, 16-bit DAC

Digital Input Modules

• SNAP-IDC5: 5 VDC digital input, TTL-compatible, 10 ms filter, optically isolated
• SNAP-IDC32: 32-channel 5–24 VDC digital input module, high-density format, 4 ms response
• SNAP-IAC5A: 85–140 VAC digital input, zero-crossing detection, 8.3 ms response time
• SNAP-IAC5: 12–32 VAC digital input, optically isolated, suitable for low-voltage AC field devices

Digital Output Modules

• SNAP-ODC5SRC: 5–60 VDC sourcing digital output, 1A per channel, solid-state relay
• SNAP-OAC5A: 85–140 VAC digital output, 3A, zero-crossing switching, optically isolated
• SNAP-ODC32SRC: 32-channel 5–60 VDC sourcing output, high-density, 0.5A per channel

Brain Boards / Communication Controllers

• SNAP-ENET-S64: Ethernet brain board, 100 Mbps, supports 64 I/O points, Modbus TCP & OptoMMP
• SNAP-PAC-EB1: PAC-series Ethernet brain, onboard IEC 61131-3 logic, 256 MB flash, dual Ethernet
• SNAP-PAC-EB2: Enhanced PAC Ethernet brain, 512 MB flash, USB programming port, expanded memory map

Serial & Communication Modules

• SNAP-SCM-232: RS-232 serial communication module, 300–115200 baud, full-duplex
• SNAP-SCM-485-422: RS-485/RS-422 serial module, multi-drop network support, up to 32 nodes

Sourcing Hard-to-Find & Obsolete SNAP Parts

The OPTO 22 SNAP series entered its mature/maintenance phase in the 2010s, with several first- and second-generation brain boards and single-channel I/O modules formally discontinued. OPTO 22 no longer manufactures SNAP-B serial brain boards, SNAP-ENET (non-S) variants, or many legacy single-channel analog modules. For plants operating on 10–25 year maintenance cycles — common in nuclear, refining, and chemical sectors — replacement sourcing is a critical operational risk.

DriveKNMS specializes in lifecycle extension support for the SNAP platform. Our inventory includes tested surplus, refurbished, and new-old-stock (NOS) units for discontinued SNAP modules. All sourced units are cross-referenced against OPTO 22's published part number history to prevent counterfeit substitution. We maintain traceability documentation for regulated industries including nuclear (10 CFR 50 Appendix B) and pharmaceutical (21 CFR Part 11) environments.

Quality Control for the SNAP Range

SNAP modules present specific test challenges due to their backplane bus architecture and optically isolated channel design. DriveKNMS applies a dedicated test protocol for all SNAP inventory:

• Backplane continuity verification: Each module is seated in a reference SNAP rack and bus communication is confirmed at the OptoMMP register level before shipment.
• Channel-level functional test: Analog input modules (including SNAP-AIV-8) are tested across the full input range (±10 VDC or 4–20 mA) using calibrated signal sources. Output accuracy is verified against published ±0.1% full-scale specifications.
• Isolation integrity check: Optical isolation barriers are tested at 1500 VAC per OPTO 22's factory acceptance criteria to confirm no degradation from prior field use.
• Firmware version audit: Brain boards are connected via Ethernet or serial and firmware revision is logged. Units with outdated firmware are updated to the last stable release prior to shipment where applicable.
• Burn-in cycle: All refurbished units undergo a 48-hour powered burn-in at ambient temperature to screen for early-life failures before dispatch.