Troubleshooting Tag Value Sync Issue Between HMI and SCADA Systems in Simatic WinCC 7.5

Question:

I am implementing both Human-Machine Interface (HMI) and Supervisory Control and Data Acquisition (SCADA) systems for my project. The HMI and SCADA both share the same tags. Adjusting the tag value on the HMI reflects the change in the SCADA system. However, when modifying the value using the SCADA system, the HMI values remain unchanged. I am intrigued by this behavior and would appreciate any insights or explanations from anyone familiar with this issue. Thank you in advance for your assistance.

Top Replies

It seems unusual. Does the PLC's value update when changed on the SCADA system? Could it be that the SCADA IO fields, tags, or connections are set as read-only?

However, every time the SCADA screen is refreshed, it resets to the HMI value. This can be a frustrating issue for users who rely on accurate data visualization in their supervisory control and data acquisition system.

This issue might likely be related to the communication hierarchy within your system. Usually, the SCADA system takes on the role of a 'master,' making it capable of pushing data to a 'slave' such as the HMI, but a 'slave' may not necessarily be able to push data back to the 'master.' You might want to consider checking your system configuration—specifically, the rights and permissions related to data writing from both ends. Also, testing how the HMI handles output data updates from the SCADA system could shed more light on the issue. Ensure your tags are set up for bidirectional communication if you want changes reflected at both ends.

It sounds like a synchronization issue between the HMI and SCADA system. Make sure that the communications protocol between both systems is set up correctly and check for polling intervals. Sometimes, the SCADA system updates faster than the HMI can accommodate, hence leaving the HMI data unchanged. You may also need to confirm the write privileges on your HMI. Adjust the settings as required and see if the values sync up accurately. Above all, rigorous testing will help you iron out the timing issue and ensure consistent functionality across both platforms.

This sounds like a synchronization issue between the HMI and SCADA systems. You need to remember that SCADA systems are typically the "top dogs" in these environments and hold superior control. Ensuring real-time data consistency in both systems is crucial. When you modify tags in your SCADA system, it isn't necessarily impacting your HMI because it might not be set up to 'listen' for changes from the SCADA system. One way to address this could be to ensure that your HMI is refreshing or polling the tag database at regular intervals to capture any changes made via the SCADA system. It would certainly take some fine-tuning, but it may be a good starting point to resolve your issue.

It sounds like you're experiencing a common issue with data binding between HMI and SCADA systems. Typically, the HMI should be designed to listen for updates from the SCADA system, so any change there should trigger an update on the HMI side. It might be worth checking the configuration or settings related to data refresh rates or event triggers in your HMI software. Sometimes, certain protocols or tags might not have the correct synchronization setup, leading to this kind of lopsided behavior. If you haven’t already, reviewing the communication settings or looking into whether the SCADA changes are being published as events could shed some light on the root cause. Hope that helps!

It sounds like you're encountering a classic issue with tag synchronization between your HMI and SCADA systems. Typically, the HMI should have a mechanism for refreshing or polling data from the SCADA, so when a value is changed in the SCADA, ideally, the HMI gets updated automatically. Check if the HMI's refresh rate is set correctly or if it's possibly caching the values instead of querying them in real-time. Additionally, ensure that the communication protocols between the systems are properly configured so they can interchange updates seamlessly. If all else fails, exploring the documentation for both systems might reveal specific settings that could resolve this inconsistency.

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Frequently Asked Questions (FAQ)

FAQ: 1. Why does changing the tag value in the HMI reflect in the SCADA system, but not the other way around in Simatic WinCC 7.5?

Answer: Answer: This behavior could be due to a configuration or synchronization issue between the HMI and SCADA systems. It is essential to ensure that the tag values are properly mapped and synchronized bidirectionally for consistent updates.

FAQ: 2. How can I troubleshoot tag value sync issues between the HMI and SCADA systems in Simatic WinCC 7.5?

Answer: Answer: To troubleshoot such issues, you can start by checking the tag mapping configurations in both systems, verifying communication settings, and ensuring data consistency between the HMI and SCADA. Additionally, reviewing system logs and monitoring data flow can help identify potential issues.

FAQ: 3. What are some common reasons for tag value discrepancies between HMI and SCADA systems in Simatic WinCC 7.5?

Answer: Answer: Tag value sync issues can occur due to misconfigured tag mappings, communication errors, network issues, or synchronization delays between the HMI and SCADA systems. It is essential to review the system configurations and data exchange mechanisms to address such discrepancies.

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