4.1 Functional Testing
Power, signals, and performance checks.
Functional testing is the proving ground where aassembled silenthardware meets reality. It transforms an inert build turns into a provenverified product.product Itby appliesapplying powerpower, safely,simulating drivesreal-world I/O with realistic loads,conditions, and comparesmeasuring realperformance measurementsagainst tostrict definedlimits. limits—noMore guesses,than just numbers.catching Recipesdefects, it creates traceable records that link every measurement, recipe, and fixturesfirmware make the steps repeatable, while a calm bring-up protects hardware from inrush and wiring mistakes. Results are tiedversion to the serialspecific numberunit, (oftenmaking throughreliability MES—manufacturingtangible. executionBy system)combining sodisciplined performance,power-up, firmware,realistic signal exercise, and proofs travel with the unit. Do this well andlocked test flows, functional testing becomes both a quietsafety gate: predictable on the line,net and a strong shield against costly field surprises.failures.
4.1.1 The mission (in one line)
Turn a silent box into a measured, proven product—apply power safely, exercise the I/O with realistic loads, compare against limits, and record the truth to the serial number.
4.1.2 Test flow that keeps you safe (and fast)
Plan → Power → Exercise → Measure → Decide → Record
- Plan — load the right recipe by SKU/Variant scan; fixtures/loads ready.
- Power — safe bring-up (current-limit, sequencing) with interlocks.
- Exercise — drive interfaces and sensors like the real world.
- Measure — voltage, current, timing, comms, thermals vs limits.
- Decide — PASS/FAIL by rules (no “it looks fine”).
- Record — push results, plots, and versions to MES by SN.
4.1.3 Fixture & station essentials
- Interlocked lid, E-stop, bleed/discharge for caps; HV/HOT beacons.
- Mating connectors (prefer over pogo) sized for current; strain-relief for harnesses.
- Programmable PSU & loads (constant current/voltage/resistance; fast foldback).
- Sensors/actuators simulators: thermistors, 4–20 mA loops, relays/solenoids, encoders.
- Network hub with known-good links; RF attenuators or shield box if radios are checked.
- Calibration assets: DMM/clamps with current certs; station self-check at shift start.
- Recipe control: test script and limits selected by scan; block manual edits.
4.1.4 Power-up sequence (don’t cook first)
- Visual pre-check: fans free, jumpers/config switches per SWI, no loose screws/FOD.
- Set limits: PSU current limit slightly above spec; electronic loads disabled.
- Apply rails in order (if required): e.g., 5 V → 12 V → 24 V; verify inrush < limit.
- Brownout test (quick): dip primary briefly; product should not latch in a bad state.
- Thermal sniff: 2–5 minutes at idle; fans spin; no hotspot beyond design expectations.
Abort if over-current trips, smoke/odor, abnormal noise. Quarantine with a ticket.
4.1.5 Signals & interfaces (exercise like the real use)
4.1.6 Performance checks (numbers that matter)
- Voltage drops under load at key test points (spec’d rails).
- Current draw: idle / typical / max; compare to golden.
- Timing: boot time, relay actuation delay, watchdog behavior.
- Throughput: network bandwidth, serial packet loss, USB speed.
- Thermals: ΔT at heatsinks after a brief load; fans meet RPM window.
- Noise (optional pre-compliance): ripple on rails, simple radiated sniff in fixture.
4.1.7 Limits & golden references
- Limits live in the recipe, versioned and locked.
- Build golden unit data sets (current, drop, timings) at NPI and after ECOs; use tolerance bands (e.g., ±10%) unless the spec dictates absolute numbers.
- Separate spec limits (must meet) from golden trends (drift detection).
4.1.8 Pass/fail logic (no vibes—just rules)
- Hard gates: safety, over-current, miswired I/O, failed storage, watchdog faults → FAIL.
- Measured gates: numeric compare to limit table → PASS only if all required rows pass.
- Retest rules: one immediate retest allowed only after a clear cause (fixture reseat, cable change). Second fail = NG-QUAR.
4.1.9 Environmental sanity (fair tests)
- Log ambient Temp/RH; some limits vary with environment.
- If the spec requires warm-up or soak, the script enforces wait times.
- For radio checks, use a shielded mini-box or attenuators to avoid the open lab RF zoo.
4.1.10 Data & traceability (what the record must contain)
Attach to the unit SN:
- Recipe ID & version, fixture ID, instrument IDs (cal status).
- Limits table used; operator and timestamp.
- For each test: stimulus (V/I/timing), measured values, PASS/FAIL, and plots where helpful (e.g., current vs time).
- Firmware image/hash, config/keys written, and results of any checksum verify.
- Photos if your SOP wants panel/label proofs at test.
4.1.11 Throughput & ergonomics (takt-aware testing)
- Pre-stage two fixtures (ping-pong) if test time ≈ takt×2.
- Parallelize long soaks off the main lane (side rack) and return for closeout.
- Use quick-connects and guided nests; no raw pin probing.
- Make common failures obvious on the UI (red tile with the failing step, not a log file hunt).
4.1.12 Starter test matrix (customize per product)
4.1.13 Acceptance cues (fast eyes)
4.1.14 Common traps → smallest reliable fix
4.1.15 Pocket checklists
Before
- SKU/Variant scanned → correct recipe/limits loaded
- Fixture interlock/E-stop OK; instruments in cal
- Loads zeroed; PSU current limit set; fans clear
During
- Power-up clean; inrush OK; no alarms
- Exercise I/O per script; measure and log automatically
- Quick thermal sniff at load; fans meet RPM window
After
- PASS/FAIL decided by rules; no manual override
- Results, plots, firmware hash bound to SN
- NG units to QUAR/REWORK with failing step noted