Which instrument setting does the source describe?
NI defines sample rate as the rate at which an analog-to-digital converter turns the input waveform into digital data. Its tutorial separately discusses input bandwidth and aliasing. These properties concern acquisition; a row timestamp in a trend export does not document all of them.
Commissioning Docs is independent and is not affiliated with NI. Use the actual instrument and historian manuals to establish how a recorded value was acquired and reduced. This worksheet does not choose a sample rate, approve a measurement chain or specify a commissioning acceptance limit.
Sources: NI: NI: Acquiring an Analog Signal, updated 3 September 2026
Which evidence belongs beside a trend file?
Keep each channel tied to the approved test requirement and equipment identifier. Obtain the actual configuration and export definition rather than infer the processing chain from a graph that looks smooth.
| Evidence field | What to record | What it cannot establish alone |
|---|---|---|
| Acquisition | Rate, instrument function and channel | Historian storage behavior |
| Input processing | Relevant bandwidth and filter reference | Adequacy for every event |
| Aggregation | Mean, maximum, last value or other stated rule | The original waveform |
| Window | Duration and timestamp convention | Clock alignment with other sources |
| Saved interval | Spacing and gaps in retained rows | Acquisition sample rate |
| Raw evidence | Whether and where raw samples are retained | A retrospective reconstruction if absent |
How can equal logging intervals preserve different information?
Illustrative example. A fictional minute contains 60 equally weighted, already acquired one-second values. Fifty-nine are zero and one is 60 signal units. A minute mean is 60 / 60 = 1 signal unit, while a minute maximum is 60. Both files can contain one row per minute and still describe different summaries.
This arithmetic is not a simulated meter, waveform or electrical test. It does not establish that the one-second acquisition captured an actual transient. A saved average of 1 cannot be expanded into the missing original sequence, and a saved maximum does not reveal its duration or shape.
How should an evidence limitation be closed?
Ask the commissioning professional to assess whether the retained processing and timing meet the actual test requirement. Preserve the original file, configuration reference and any limitation. Do not fill missing raw samples with interpolated values labeled as measurements.
If additional evidence is required, follow the authorized test and safety process. This site prepares documentation and does not perform testing. Engineering sign-off is performed only by the registered engineer on the job.
Common questions
What else should the bid team know?
Is one row per minute proof of one sample per minute?
No. The saved interval and acquisition rate are separate settings.
Can a minute average recreate a short peak?
No. Obtain the actual retained evidence and processing definition.
Does this worksheet prescribe a safe sample rate?
No. The responsible technical reviewer decides the required measurement chain.