Two production measurements can use the same function and units while using different instrument ranges. A range change can alter the applicable measurement specification and the time needed to obtain a reading. Record range behavior when comparing stations or investigating a discontinuity in test data.
Keysight’s DMM throughput discussion identifies autoranging as a contributor to measurement time. That observation does not mean manual range is always preferable. The selected range must also accommodate the product’s expected behavior and the intended measurement accuracy.
Identify the range policy
Determine whether the recipe requests a fixed range, autorange, or an initial autorange followed by a held setting. Read back the actual configuration where supported. A software variable named range may describe a requested limit rather than the range ultimately selected by the instrument.
Include the measurement function, instrument model, range, integration settings, and relevant filtering in comparison records. Values exported without their configuration can make an instrument behavior look like a board revision effect. Include range changes within a step when several readings contribute to its final reported value.
Investigate boundary behavior
| Observation | Check |
|---|---|
| Sudden change in resolution | Range transition or display formatting change |
| Occasional longer test step | Autorange activity and settling behavior |
| Overrange result | Actual signal and selected range |
| Stations disagree near a threshold | Range policy and applicable uncertainty |
Use a controlled signal or stable reference to explore the region around an observed transition. Keep the source and connection method unchanged while changing the range policy. Record raw readings and status so that formatting does not conceal overrange or invalid measurements.
Choose a production policy deliberately
- Define the signal envelope that the test must measure.
- Check suitable ranges against the instrument documentation.
- Evaluate measurement variation and cycle time for candidate settings.
- Handle unexpected out-of-range signals explicitly.
- Release the selected policy with its supporting evidence.
A fixed range can improve predictability when the signal envelope is controlled, but it can also turn an unexpected product state into an invalid reading. Do not coerce that condition into an ordinary numeric failure or silently reuse an earlier value. Preserve the distinction between a measured out-of-limit result and an unmeasurable condition.
After changing the policy, compare representative boards across the affected operating states. A faster average cycle time does not establish that all test steps retained their meaning. Keep the old and new configurations identifiable so that trends collected before and after the change are interpreted with the correct measurement context.
Move from reading to a build-ready project
Use the fabrication and assembly checklists to prepare drawings, production files and test requirements.
Open the DFM checklist