Sensor Message Age: Separate Clocks From Transport Delay
Review message-age measurements against timestamp origin, clock alignment and queueing before interpreting robot sensor transport performance. This guide concerns robot integration and delivery review. The proposed observations are editorial assessment guidance, grounded in the linked original documentation and subject to the deployed version. They do not describe an on-site test of a particular machine or establish whole-system acceptance from a single interface response.
Locate timestamp creation
Identify whether the timestamp represents acquisition, driver reception or message assembly. Processing can already have occurred between those points. Draw the path from acquisition to subscription and mark the two instants used by the statistic. The same reported age can therefore describe different boundaries on two otherwise comparable devices.
For this review, identify the delivered device, software and configuration revisions first. Record unsupported, disabled and untested capabilities separately. Evidence from another model is useful context, but cannot establish what the delivered combination actually provides. Keep the original input beside the settings used to interpret it.
Check clocks before differences
Record the clock supplying the header and the clock used at reception, together with alignment evidence. A stable number can contain a stable clock offset. Retain negative values and investigate clock provenance or timestamp creation rather than clamping them to zero and presenting the modified series as the original measurement.
Retain the original input and the reason for the decision, rather than a successful screenshot alone. Change only the variables agreed for the comparison, and keep the before-and-after configuration. List conditions that were not exercised explicitly; they should not silently become part of the accepted operating range.
Separate candidate stages
A large age can include acquisition processing, publishing queues, transport and receiver scheduling. A subscription-side aggregate cannot identify which contribution dominates. Add observations at appropriate boundaries when localisation is required. Use the evidence matrix to choose the next recording point rather than assigning a component failure from one aggregate.
Use the three illustrated observations as starting questions, rather than as diagnoses of an installation that has not been inspected. Check record completeness, units and identity before selecting the next observation. An unresolved result is more informative than a confident explanation assembled from missing fields or unrelated test runs.
Retain interpretable samples
Keep representative original headers, reception records and their collection window. Confirm that records belong to the same subscription and run, and identify the aggregation method. Compare devices using consistent workload and observation boundaries. Ranking age values derived from different timestamp definitions would mix interface conventions with the behaviour being assessed.
Let the site owner choose an approved isolated way to exercise relevant exceptions. Record normal operation, the exceptional condition and recovery separately. The purpose is to establish how the application recognises and explains untrustworthy input, without requiring production equipment to act on deliberately invalid results.
Report the measured boundary
Deliver timestamp meaning, receiving clock, alignment evidence, window and unobserved stages with the result. Describe an age measurement as an age measurement. A network-only one-way delay claim requires observations that establish that network boundary; removing unknown contributions by assumption cannot turn the existing aggregate into that separate measurement.
Deliver the configuration, representative samples, result table and unresolved questions together. Agree who reviews subsequent changes. The receiving team should be able to select one conclusion and trace it back to its input and decision path without relying on the original author to reconstruct the missing steps.
Original documentation and further reading
Continue with related articles in this section, or use selection guides to prepare the next review. Apply the device-specific documentation and agreed operating conditions when implementing a test.