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| Part Number: | RET670 1MRK004816-AC | Family/Series: | AC800M |
| Product Type: | PLC Communication Module | Category: | Home/DCS/DCS Systems/Profibus Module |
| Plance of Origin: | Made in USA | Product Status: | Popular Product |
Title: Understanding PROFIBUS PA Connectivity and Signal Polarity
Introduction: PROFIBUS PA devices primarily utilize multibarriers or T-junctions for network connectivity. This article delves into the organization of these devices, their connectivity options, and the importance of signal polarity.
RET670 1MRK004816-AC Redundant Structure ▏ ABB Automation
- Device Connectivity:
- Most PROFIBUS PA devices connect to the network using multibarriers or T-junctions.
- Spur connections are made directly to the connector block inside the device.
- M12 plugs are sometimes employed for network connections (refer to Bus connector on page 67).
- MBP Technology and Polarity:
- MBP technology ensures correct functionality even with incorrect field device connections (e.g., polarity reversal) due to automatic polarity detection.
- The Manchester signal in fieldbuses is an alternating voltage; incorrect device connections may result in inverted signals, hindering communication.
- Polarization of Fieldbus Signals:
- Fieldbus signals are polarized, and devices must be connected to see the signal in the correct polarity.
- Non-polarized field devices are available, typically network-powered, allowing connection in either polarity.
- Proper network construction involves connecting all (+) terminals and (-) terminals to each other for devices with polarization.
- Considerations for Ex Applications:
- For Ex applications, insulation voltage and single conductor insulation must adhere to EN 60079-14, and characteristic values in line with the FISCO model should be maintained.
- Device Power Polarity:
- Bus-powered field devices may be polarized with respect to device power.
- Polarity alignment ensures that signal and power polarity are consistent, simplifying connectivity.
- MBP Cycle Time Calculation:
- PROFIBUS-PA data telegrams in MBP transmission resemble asynchronous RS-485 transmission.
- MBP segments feature bit-synchronous transmission with preambles and start and end delimiters.
RET670 1MRK004816-AC Redundant Structure ▏ ABB Automation
Conclusion: Understanding PROFIBUS PA connectivity, signal polarity, and device considerations is crucial for building robust and efficient networks. Proper planning ensures seamless communication and allows for future expansion with polarized devices if needed.
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