Description
The Omron SR125SMS4503 is a stop motion sensing unit designed to monitor motor deceleration by detecting residual back electromotive force (back-EMF). It confirms when rotating machinery has reached a safe stop before enabling guard unlocking or machine access. The Omron SR125SMS4503 is widely used in industrial safety systems to improve personnel protection and machine control.
Technical Specifications
| Condition |
New/Never Used Surplus |
| Brand |
Omron |
| Category |
Safety Equipment |
| Part Number |
SR125SMS4503 |
| Subcategory |
Stop Motion Sensing Unit |
| Device Type |
Safety Monitoring Relay |
| Supply Voltage |
24 VDC |
| Power Consumption |
≤ 3.0 W |
| Detection Method |
Back-EMF sensing |
| Detection Threshold |
Adjustable from 0.01 V to 0.10 V |
| Safety Outputs |
1 N/O and 1 N/C relay contacts |
| Auxiliary Outputs |
2 solid-state signaling outputs |
| Mounting |
35 mm DIN Rail |
| Protection Rating |
IP40 housing, IP20 terminals |
| Operating Temperature |
-10°C to +55°C (14°F to 131°F) |
| Approvals |
UL, CSA, TÜV, CE, EN ISO 13849-1, EN62061 |
| Weight |
0.45 kg (0.99 lb) |
Information About SR125SMS4503
The Omron SR125SMS4503 is a compact stop motion sensing unit designed to detect when motors have completely stopped by monitoring residual voltage (back-EMF). As part of Omron’s safety relay lineup, this unit provides secure monitoring of motor deceleration for safe interlocking of guards and brakes. Featuring adjustable sensitivity and solid-state auxiliary outputs, the SR125SMS4503 ensures precise and reliable zero-speed detection. Although now discontinued, it remains widely used in legacy motor control safety applications.
Key Features:
- Back-EMF Detection: Monitors motor winding voltage to confirm stop condition before releasing safety interlocks.
- Relay and Solid-State Outputs: Provides one N/O and one N/C relay output plus two auxiliary semiconductor outputs for signaling zero-speed status.
- Adjustable Threshold: Detection voltage threshold adjustable from 0.01 V to 0.10 V for tuning to various motor types.
- DIN-Rail Mountable: Compact design for easy integration into industrial control cabinets.
- 24 VDC Supply Voltage: Low power consumption (150 mA) simplifies integration into safety circuits.
- IP40 Housing / IP20 Terminals: Designed for installation within protected electrical enclosures.
- High Reliability and Safety Compliance: Certified to EN ISO 13849-1, UL, and TÜV standards for safety relay applications.
- Diagnostic LEDs: Visual indication of operating status and error conditions.
- Discontinued Model: Available through surplus and aftermarket channels for supporting legacy equipment.
The Omron SR125SMS4503 provides dependable, zero-speed detection for machine safety systems, helping prevent access to hazardous areas until motor motion ceases. Its reliable back-EMF monitoring, flexible outputs, and safety certifications make it a trusted solution for ensuring operator protection in legacy motor-driven applications.
