Sensonics Sentry G3 Machinery Protection System vs Istec SpeedSys® 300
In turbomachinery, overspeed protection is critical to preventing failure and ensuring compliance. To help you come to the best decision in choosing the right system, we’ve put out a comparison. In this comparison, we’ll be looking at the The Sensonics Sentry G3 Machinery Protection System and Istec SpeedSys® 300.
The Sensonics Sentry G3 Machinery Protection System provides overspeed protection through its Sentry G3 OSP functionality as part of a rack‑based machinery protection platform.
Why forward-thinking OEMs, integrators, and end users choose SpeedSys® 300
Established brands often continue to build on existing architectures for many years, leaving limited room to incorporate user feedback or modern application requirements. Istec, however, has developed its latest systems from the ground up, with a clear focus on today’s needs in machine protection and monitoring.
As a result, SpeedSys® 300 not only covers the core overspeed protection functions traditionally expected from established solutions, but also extends them with a compact modular design, support for multiple sensor types, configurable outputs, modern communication options, and clearly specified response characteristics. This allows users to implement proven protection concepts while benefiting from additional flexibility and transparency that are increasingly important in both new installations and retrofit projects.
Sensonics Sentry G3 Machinery Protection System
Istec SpeedSys 300
Proven-in-use
Certified by design
SpeedSys® 300 is designed with functional safety embedded directly into the system architecture. SIL 2 and SIL 3 capability are integral to the product design and depend on the applied redundancy configuration, rather than being added as an external system layer.
(Background on this approach: Het verschil tussen SIL-certificering door ontwerp en proven in use)
System‑integrated protection concept
Sentry G3 is a rack‑mounted machinery protection system that integrates sensor conditioning, monitoring, alarming and protection functions within a single platform. Multiple measurement types (vibration, speed, expansion, temperature and others) are handled within one system architecture.
Standalone protection concept
Each SpeedSys® 300 module performs a complete overspeed protection function independently, clearly separating protection functionality from control and monitoring systems.
Integrated redundancy approach
Redundancy is implemented at system level through rack‑based architecture, dual‑redundant power supplies and configurable cross‑channel voting. Overspeed protection can be implemented using high‑integrity 2oo3 voting configurations within the system.
Modular redundancy approach
Redundancy is achieved by combining multiple SpeedSys® 300 modules, supporting flexible 1oo1, 1oo2, or 2oo3 voting architectures at system level.
Integrated safety outputs
Each channel provides alarm relays and configurable analog outputs. Additional alarm I/O and voting logic are available through rear terminal connections, enabling flexible integration with trip and control systems.
Integrated safety I/O
Safety relays and a safety‑related analog output are available directly on the device, reducing external safety hardware.
Backplane‑based system design
Sentry G3 is designed as a 19‑inch rack‑mounted system with a shared backplane. Plug‑in modules support hot‑swapping and centralized system infrastructure, including power supplies and communications.
Compact and practical design
SpeedSys® 300 is installed as an individual DIN‑rail mounted device. Multiple units can be mounted side‑by‑side to implement redundancy concepts without requiring a shared rack, backplane, or central baseplate.
Communication for diagnostics
The system supports Modbus RS‑485 communications and USB connectivity for configuration, diagnostics, data retrieval and integration with higher‑level plant systems.
Communication for diagnostics
Modbus RTU over RS‑485 is provided for monitoring and diagnostics only and is not part of the safety function.
Centralized installation concept
Sentry G3 operates as a centralized machinery protection and monitoring system. Protection, alarming and voting logic are implemented at system level rather than as independent standalone protection devices.
Standalone and distributed installation
The compact footprint supports space‑constrained installations and retrofit projects, while maintaining full overspeed protection functionality within a single module.
Lifetime Support
SpeedSys 300 delivers a clean architectural separation between control and trip logic ensuring uncompromised protection compared to integrated systems.
SIL3 by Design
Adapt as needed: from single-channel setups to fully redundant 2oo3 architectures, SpeedSys 300 supports stepwise scalability at every stage.
Compact Footprint and Seamless Integration
Engineered for space-limited panels and demanding environments, it’s ideal for both retrofits and new installations.
FAQ
Yes, it’s an independent overspeed protection system, aligned with the requirement that overspeed protection be separate from the control system.
Yes, both systems support redundant architectures such as 2oo3, but they implement redundancy in different ways. Istec SpeedSys® 300 supports redundant architectures up to 2oo3 by using multiple independent SpeedSys units that are hard‑wired together, allowing redundancy to be implemented externally while each unit remains a standalone overspeed protection device. Sensonics Sentry G3 also supports voted architectures including 2oo3, but this functionality is implemented within the rack‑based Sentry G3 Machinery Protection System, where overspeed protection is provided via the Sentry G3 OSP functionality as part of the overall platform, using multiple channels and system‑level voting logic.
Neither system supports Profibus‑based DCS integration.
Istec SpeedSys® 300 provides Modbus RTU over RS‑485 for monitoring and diagnostics, and does not list Profibus as a supported interface. Sensonics Sentry G3 (including the OSP overspeed functionality as part of the Sentry G3 Machinery Protection System) provides Modbus RS‑485 and Ethernet interfaces for system integration, but Profibus support is not specified.
Istec ensures the availability and safety of your rotating machinery by providing the most convenient and accessible hardware solutions, delivered by the world’s leading vibration and speed sensing experts.
Accuracy disclaimer
All of our comparison pages have been filled in to the best of our knowledge, using publicly available sources. However, we cannot guarantee that they are fully up-to-date or completely correct.
| Sensonics Sentry G3 Machinery Protection System | Istec SpeedSys® 300 | |
|---|---|---|
| Key features | Multi‑channel machinery protection system; vibration, speed, expansion and temperature monitoring; rack‑based architecture; integrated displays; API 670 compliant | Overspeed, underspeed and acceleration detection; modular redundancy; compact standalone design; Modbus diagnostics |
| Hardware response time | Reaction time < 10 ms (OSP overspeed functionality) | ≤ 8 ms (relay hardware response time) |
| Frequency range | 0.02 Hz to 20 kHz (speed measurement) | 0.025 Hz to 35 kHz |
| Number of relays | Up to 4 measurement channels per module; channels independently configurable | 1 input per module (only one sensor input active at a time) |
| Number of relays / outputs | 1 alarm relay per channel; expandable alarm I/O at rear terminals | 2 safety relays per module plus additional signal outputs |
| Voting system | Supports cross‑channel voting; high‑integrity 2oo3 overspeed configuration available in system architecture | 1oo1 (single module); 1oo2 or 2oo3 using multiple modules (external voting) |
| Outputs | • 2 × analog outputs per channel (4–20 mA or 0–10 V) • Buffered transducer outputs (front & rear) • RS‑485 Modbus communications | • 1 × safety‑rated 4–20 mA analog output • 1 × binary output • 1 × frequency output • Modbus RTU (RS‑485, diagnostics only) |
| Input voltage | Module supply: +24 VDC ± 5%; rack supply: 90–264 VAC or 24 VDC (redundant PSU option) | 24 VDC (18 – 36 VDC), dual-redundant power supply |
| Functional safety | IEC 61508 SIL 3 overspeed protection (system configuration) | SIL 2 / SIL 3 capable; functional safety embedded in system design |
| Stand‑alone protection | Not specified as a standalone overspeed device; operates as a rack‑based system [Sentry G3...on System) | PDF] | Yes – each module performs a complete overspeed protection function independently |
| Relay information | SPDT alarm relay per channel; switching capacity not specified for safety use | 2 × safety relays (DPST); max. 30 VDC / 2 A (resistive) |
| Rack / backplane mounting | Yes – 19‑inch rack‑mounted system with shared backplane | Optional 19‑inch rack for mechanical mounting only; no shared backplane or internal bus |
| Reserve scalability | Scalable rack‑based system with up to 24 channels per 3U rack | Scalable from single module (SIL 2) to redundant multi‑module SIL 3 configurations |