Ensuring Industrial Safety: The Vital Functions of Pilz Relays

What is a Pilz relay?

  • A Pilz relay, commonly referred to as a Pilz safety relay, is an essential part of systems for industrial automation and machinery safety.
  • These relays are created by Pilz, a reputable producer of safety automation devices, to guarantee the safe operation of machinery and safeguard both employees and equipment from injury.
  • In the framework of safety automation, Pilz relays perform a number of crucial tasks.

What is the purpose of a safety relay?

Safety Monitoring:

  • The main function of Pilz relays is safety monitoring.
  • They continuously evaluate the state of several safety-related conditions and inputs in a manufacturing environment.
  • These inputs can include safety sensors, safety gates, emergency stop buttons, and more.
  • Pilz relays are critical in maintaining a safe working atmosphere by monitoring these inputs.

Emergency Stop Function:

  • The emergency stop (E-stop) function is one of the Pilz relay’s most important roles.
  • The relay quickly cuts off the electricity to the machinery in the event of an emergency, such as a worker in distress or a dangerous condition discovered by a safety sensor.
  • This immediate shutdown can save accidents from happening and safeguard people from damage.

Safety Interlocking:

  • For machinery or production processes, Pilz relays are employed to regulate access to dangerous areas.
  • For instance, before allowing the machine to work, they can make sure that a safety gate is tightly closed.
  • This interlocking system aids in preventing unsafe or unauthorized access to risky areas.

Monitoring Safety Sensors:

  • Industrial environments frequently use safety sensors including light curtains, safety mats, and safety switches.
  • Pilz relays are made to continuously check the status of these sensors.
  • The relay can start a safety response, such as stopping the machine or raising an alarm, if a sensor detects a safety breach, such as an object or person entering a restricted area.

Guarding and Perimeter Protection:

  • Pilz relays are essential for perimeter safety and protection. They can keep an eye on barriers, fencing, or safety measures.
  • The relay can immediately respond to stop the machinery in the event that a guard is removed, tampered with, or if an unauthorized entrance attempt is made. This prevents accidents and injuries.

Handling Multiple Inputs:

  • These relays may simultaneously process several inputs from different safety devices.
  • They assess the inputs and determine whether it is safe to let the machine run normally or whether an emergency stop is necessary.
  • Due to their adaptability, they can be used in manufacturing environments with a variety of sophisticated safety needs.

Fault Tolerance:

  • Redundancy and self-monitoring characteristics are included into Pilz relays.
  • The relay can make adjustments to preserve safety if a part inside it malfunctions or a fault is found.
  • This guarantees that the level of safety will not be compromised even in the event that there is a malfunction.

Reset and Restart Functions:

  • Pilz relays can perform reset and restart operations following the resolution of an emergency stop condition.
  • These features allow for the safe restart of machine operations, avoiding unanticipated restarts that may harm employees.

Safe Control of Robots:

  • Pilz relays can be used in robotics applications to regulate the robots’ safe operation.
  • This guarantees that robots operate within established safety limitations and do not endanger adjacent workers.


  • Pilz relays are integral components of industrial safety systems, helping industries comply with safety standards and regulations while safeguarding workers and equipment.
  • Their multifaceted functions, including emergency stop capabilities, safety interlocking, sensor monitoring, guarding, fault tolerance, and more, contribute to the prevention of accidents and the promotion of workplace safety.
  • Implementing Pilz relays in industrial settings not only protects personnel but also helps maintain the integrity and reliability of industrial processes.
  • Adherence to relevant safety standards and guidelines is essential when integrating Pilz relays to ensure the highest level of safety in industrial automation.

What diagnostic features are available on Pilz safety relays, and how can they be utilized to troubleshoot system issues?

Pilz safety relays are critical components used to ensure the safety and proper functioning of industrial automation systems. They come with various diagnostic features that help in troubleshooting and maintaining the system. Here are the key diagnostic features available on Pilz safety relays and how they can be utilized to troubleshoot system issues:

1. Status LEDs

Pilz safety relays are equipped with status LEDs that provide immediate visual feedback about the relay’s status. These LEDs typically indicate:

  • Power supply status (often labeled as “PWR” or “24V”)
  • Input status (indicating the state of safety inputs)
  • Output status (indicating the state of the safety outputs)
  • Error or fault status (indicating specific faults or errors)


  • Power LED: Ensure the relay is receiving the correct supply voltage. If the power LED is off, check the power connections.
  • Input LEDs: Verify that the safety devices (e.g., emergency stop, light curtains) are correctly wired and functioning. The input LED should change state when the corresponding safety device is activated.
  • Output LEDs: Check the status of the safety outputs. If an output LED is off when it should be on (or vice versa), it may indicate an issue with the safety logic or external devices connected to the relay.
  • Error/Fault LED: Refer to the relay’s manual for specific fault codes indicated by blinking patterns or colors of the error LED. This can point to issues like wiring faults, configuration errors, or hardware failures.

2. Diagnostic Interfaces

Some advanced Pilz safety relays come with diagnostic interfaces such as serial ports or network interfaces (e.g., PROFIBUS, PROFINET, Ethernet/IP). These interfaces allow for more detailed diagnostic information to be accessed via software tools or PLCs.


  • Connect to Software Tools: Use Pilz diagnostic software (e.g., PNOZmulti Configurator) to connect to the relay via the diagnostic interface. This software can provide detailed information about the relay’s status, error logs, and system configuration.
  • PLC Integration: Integrate the safety relay’s diagnostics into a PLC system. Diagnostic data can be read by the PLC and displayed on an HMI (Human-Machine Interface), allowing operators to monitor the safety system in real time.

3. Error Memory

Pilz safety relays often have built-in error memory that logs fault conditions and operational events. This memory can retain information even after a power cycle.


  • Access Error Logs: Use the diagnostic software or interface to read the error memory. Analyze the logs to identify recurring issues or the sequence of events leading to a fault.
  • Historical Analysis: Error logs can help in understanding the history of faults and aid in identifying patterns that may indicate underlying issues in the system.

4. Test and Reset Functions

Many safety relays feature test and reset buttons or terminals that can be used to verify the relay’s operation and reset fault conditions.


  • Perform Tests: Use the test function to simulate input conditions and verify that the relay responds correctly. This can help in ensuring that the safety functions are operational.
  • Reset Faults: Use the reset function to clear fault conditions after troubleshooting. If a fault persists after reset, it may indicate a persistent issue that needs further investigation.

5. Communication Protocols

Advanced relays support communication protocols that allow for remote monitoring and diagnostics.


  • Network Monitoring: Use industrial network monitoring tools to track the status of the safety relay over the network. This can provide real-time alerts and detailed diagnostic data remotely.
  • Integration with SCADA: Integrate the relay’s diagnostics into a SCADA (Supervisory Control and Data Acquisition) system to centralize monitoring and control of the safety systems.

Practical Steps for Troubleshooting

  1. Visual Inspection: Start with a visual check of the LEDs to identify any obvious issues.
  2. Check Wiring: Verify all connections and ensure there are no loose or damaged wires.
  3. Consult the Manual: Refer to the relay’s manual for specific diagnostic codes and troubleshooting steps.
  4. Use Diagnostic Tools: Connect diagnostic software to get detailed insights into the relay’s status and error logs.
  5. Test Functions: Utilize the test and reset functions to ensure the relay operates correctly and to reset any faults.
  6. Analyze Error Logs: Review error logs to identify patterns or recurring issues.

By these diagnostic features, you can effectively troubleshoot and maintain the safety and reliability of your industrial automation system.