4/27/2019 9:45 PM | |
Joined: 9/27/2006 Last visit: 12/26/2024 Posts: 12315 Rating: (2695) |
Hello newbiplc; First point: the "dark" test is not a Siemens development or Safety applications. As you can see from the various links below, especially the last, it is a requirement from IEC 60204-1 Safety of machinery standard on the availability of F-DOs during process control: VersaSafe - Test Pulses of Safe Output Modules - GE Customer Center Safety Programmable Controller/Safety Controller ... - Mitsubishi Electric Integrated Safety - Rockwell Automation Standard EN 60204-1 - Safety of machinery - User Interface Basically, and as the document you point to explains quite well, the dark (or light) tests consist of regular, (Siemens uses a period of 15 minutes initially) very short pulses sent to the F-DOs during operation. The response of the F_DO is monitored and evaluated; if the "0" signal (for dark test) is detected, then the F-DO is considered functional, and no further step is taken. If it is not detected within a specified interval, then the test is repeated at 1 minute intervals, and then the module may be passivated, or the output relay de-activated to preserve the Safety function. Now understand that you want these test pulses to affect the monitoring circuit only, not the actual output of the F-DO. If your actuator is too sensitive and is affected by the test pulse, then your program might not function as you wish, and therefore put the personnel at risk.. In our Safety applications, I do not remember having that sort of problem affect our actuators, their response time was generally very tolerant of the short test pulses sent to the F-DO. Actually you will find that the Sirius 3SK2 relays (for one) are designed to handle the F-DO dark test, and the 3RT2 relay must connect through a resistor to a 3ST2 to preserve the dark test function;: - Manual - SIRIUS 3SK2 Safety Relays https://support.industry.siemens.com/cs/ww/en/view/109444336 - Confirmation regarding connection of 3RT2 contactors and contactor assemblies to 3RK3 MSS, 3SK1 and 3SK2 safety relays. https://support.industry.siemens.com/cs/ww/en/view/109481229 When connecting a 3RT203.-. NB3.-.... and 3RT203.-.KB4.-.... to a 3SK1 Advanced 3SK1122-.CB4. relay with adjustable OFF-delay time, an additional 1.2 kΩresistor must be connected in parallel to A1-A2 on the 3RT20. Hope this helps, Daniel Chartier |
Last edited by: dchartier at: 04/27/2019 21:51:24 |
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