A test program can use the correct channel name while the fixture contacts the wrong pad. The error may originate in a harness drawing, connector view, switch configuration, or software alias. Verify the complete route instead of checking each document independently and assuming their labels agree.
NI’s switch connector reference directs users to model-specific pin-to-channel mappings. Use the documentation for the installed hardware; similar connectors and adjacent switch models do not establish interchangeable assignments.
Build one route table
For every critical measurement or stimulus, connect the logical signal name to the instrument terminal, switch route, harness conductor, fixture connector cavity, probe position, and PCB reference point. Include return paths. A correctly routed positive lead is not enough when its reference connects somewhere unintended.
Record connector viewing direction and distinguish pin numbering from drawing coordinates. Where a fixture uses interchangeable inserts, include the insert revision and its permitted board variants. A generic fixture name should not hide a changed contact pattern.
Use independent observations
| Verification layer | Useful evidence |
|---|---|
| Physical harness | Continuity to identified connector cavities |
| Probe location | Position against the board drawing or approved artifact |
| Software route | Observed response to a controlled reference connection |
| Unselected paths | Required isolation and absence of unintended connections |
Use safe reference connections or a dedicated verification artifact before applying production stimulus to an unknown route. Follow the fixture’s approved de-energization and instrument protection procedure. A channel-map check must not introduce voltage into circuitry that was not designed to receive it.
Check more than the successful route
- Select one logical test channel through the production software.
- Verify the intended physical endpoint and return.
- Inspect relevant adjacent or mutually exclusive routes.
- Repeat for different switch banks, return configurations, and fixture positions.
- Record discrepancies against the exact hardware and software revisions.
A symmetric reference artifact may conceal swapped channels because both locations produce the same reading. Choose distinguishable, controlled conditions where necessary to demonstrate identity, rather than merely demonstrating continuity somewhere in the fixture.
After a correction, repeat the affected routes and any shared connections that may have changed. Retain the completed route table as part of fixture release evidence and use it when replacing cables or probes. Do not treat a passing product run as a substitute for mapping verification when the product itself cannot expose a swapped pair.
The fixture maintenance guide explains how to preserve later changes so the verified map continues to describe the installed fixture.
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