Find where the value stops changing

1. Check that the external client is still sending reads and receiving successful responses. A displayed last value can remain after communication fails.
2. Confirm the field device's own measurement update rate. A fast poll cannot create newer data than the device measures.
3. Check whether SB1000's register cache is enabled. In firmware with this feature it defaults to off; its configurable lifetime is 1–60 seconds, with 5 seconds as the default when used.
4. Inspect cache ages/hits where available. A cache hit can answer a request without a new RS485 transmission.
5. Use a Diagnostics one-shot read of the documented point to obtain a bus request that bypasses this cache on firmware with this feature. Compare its raw reply with the client's raw result during a known field change.
6. If both are slow, reduce competing polling and investigate absent devices, retries, serial timeouts, or another master. If the raw data changes but the display does not, examine the client point's update/deadband/display settings.

Choose polling and maximum acceptable data age for the point's purpose. A successful cached response and a fresh field measurement are different events.

Expected result

The measured delay is understood and acceptable, and communication failures are represented with appropriate quality/age in the receiving system. Include timestamps, cache settings, and raw comparisons if it is not.