How to measure the performance of a daisy chain?
Issue:
Poor performance is observed on serial devices connected through an Ethernet gateway.
Product Line:
Power Monitoring Expert 9.0
Power Monitoring Expert 2020
Power Monitoring Expert 2021
Power Monitoring Expert 2022
Power Monitoring Expert 2023
Power Monitoring Expert 2024
Environment:
Diagnostics Viewer
Cause:
Too many devices are configured on the RS‑485 daisy chain, or one or more devices on the chain are experiencing intermittent communication. As a result, the daisy chain becomes saturated, leading to degraded performance.
Resolution:
- In Management Console, verify that all devices on the daisy chain being tested are enabled.
- Apply the desired system load to the devices on the daisy chain (for example: Vista, VIP, OPC, Diagrams, Tables, or Log Inserter).
- Open Diagnostics Viewer, drill down into Communications Diagnostics, and select the site associated with the daisy chain.
- Select the Communication Status tab.
- Note the current time, then right‑click in the Communication Status panel and select Reset.
- Allow the system to gather metrics:
- For real‑time data loads, a few minutes is typically sufficient.
- For logging activity, allow the test to run for approximately one hour, depending on logging intervals.
- Review the Util (%) column:
- A value at or near 100% indicates the daisy chain is saturated and is likely the cause of the poor performance.
Recommendation:
If you are using an older version of PME, consider upgrading to the latest version for improved protocol support and security. For assistance with integration or upgrades, contact Schneider Electric Technical Support at: pmo.support@se.com