Safety relays and ordinary relays serve different purposes and are designed with distinct features to meet specific requirements, particularly in terms of safety and reliability. Here are the key differences between a safety relay and an ordinary relay:

1. Purpose:

   • Safety Relay: Safety relays are specifically designed to ensure the safety of machinery, equipment, and processes by monitoring safety-related functions, such as emergency stop buttons, safety gates, light curtains, and interlocks. They are used to implement safety functions that comply with industry safety standards and regulations, such as EN ISO 13849 and IEC 61508.
   • Ordinary Relay: Ordinary relays, also known as general-purpose relays, are used for various control and switching applications in industrial, automotive, and consumer electronics. They are typically used to control power circuits, signal circuits, and automation systems, such as controlling motors, heaters, lights, and solenoid valves.

2. Safety Functions:

   • Safety Relay: Safety relays incorporate features such as redundant channels, self-monitoring, and forced-guided contacts to ensure reliable operation and prevent dangerous failures. They are used to implement safety functions such as emergency stop, safety gate monitoring, two-hand control, and safety mat monitoring.
   • Ordinary Relay: Ordinary relays do not include specific safety features and are not intended for safety-critical applications. They are primarily used for non-safety-related functions such as switching power or signals on/off in control systems.

3. Safety Standards and Certification:

   • Safety Relay: Safety relays are designed, tested, and certified to comply with specific safety standards and regulations, such as EN ISO 13849 and IEC 61508. These standards define requirements for functional safety, reliability, diagnostic coverage, and fault tolerance of safety-related systems and components.
   • Ordinary Relay: Ordinary relays may not be certified for safety-critical applications and may not comply with safety standards. They are generally designed for general-purpose switching and control tasks and may not provide the level of reliability and safety required for safety-related functions.

4. Diagnostic Features:

   • Safety Relay: Safety relays often include diagnostic features such as self-checking, fault detection, and feedback monitoring to ensure proper operation and detect any faults or failures that could compromise safety.
   • Ordinary Relay: Ordinary relays may not include advanced diagnostic features and may rely on external monitoring or testing to detect faults or failures.

5. Reliability and Failure Mode:

   • Safety Relay: Safety relays are designed for high reliability and are typically built with redundant circuits, self-checking functions, and forced-guided contacts to minimize the risk of failure and ensure safe operation.
   • Ordinary Relay: Ordinary relays may have a lower level of reliability compared to safety relays and may not be suitable for critical applications where safety is a primary concern.

In summary, while both safety relays and ordinary relays are used for switching and control applications, safety relays are specifically designed and certified to ensure the safety of machinery and equipment by implementing safety functions and complying with safety standards and regulations. Ordinary relays, on the other hand, are intended for general-purpose switching tasks and may not provide the level of reliability and safety required for safety-critical applications.