How to design a production test fixture.

Test what manufacturing can break.

Prioritise shorts, opens, wrong parts, solder defects, power rails, current consumption, programming, sensors, communications and outputs. Functional tests should cover high-risk paths rather than replay the entire user interface. Define limits from measured good units and engineering tolerances.

Make contact repeatable and safe.

Place accessible test pads with adequate spacing, unambiguous ground references and mechanical datum points. Use current-limited supplies and interlocks for dangerous loads. The fixture must tolerate operator error without damaging the unit or silently passing it.

Treat data as part of the fixture.

Store serial number, hardware revision, firmware hash, calibration values, individual measurements, result and timestamp. Separate retest from first pass and preserve failure codes. These records connect field returns to production evidence.

Case study: testing every ELPM module.

The first ELPM fixture prototype was developed to avoid random sampling: every module goes through at least two test cycles. The sequence checks component operation, measures current in the extreme-low-power waiting state and exercises the SX1262 LoRa RF front end. Results are stored in the internal database to connect serial number, measurements and retest history.

One of the most sensitive points was not software but the pin-to-socket contact. Pressure, alignment, wear and contamination can create false failures or false passes. The contact system is therefore treated as a measurable, maintainable part of the fixture rather than a mechanical accessory.

When to involve an engineering partner.

An independent review is most valuable before the PCB, enclosure, firmware architecture or pilot batch is frozen. OBJEX LABS can review hardware, firmware, testability, compliance and the manufacturing path, then define a scoped phase with clear deliverables and acceptance criteria.