4.13 Final Electrical Validation (CIR/HIPOT)

Visual inspection confirms workmanship, but only electrical validation confirms function. A harness with perfect crimps and routing is useless if the pinout is swapped or a stray strand creates a hidden short. Final electrical testing is the mandatory "Quality Gate" that verifies the assembly against the schematic logic (Continuity) and the safety insulation requirements (Hi-Pot).

4.13.1 Continuity Testing: The Logic Check

Continuity testing verifies that current flows where intended. It validates the "Netlist" — the map of Point A to Point B.

100% Verification Mandate

Testing must be performed on 100% of production units. Sampling is prohibited for electrical connections because a single mis-pinned connector is a functional failure.

• Pin-to-Pin Mapping: The tester cycles through every pin to ensure it connects to the correct destination. This detects Cross-Wiring (swapped pins) and Open Circuits (missing wires or unseated terminals).
• Threshold Resistance: The tester does not just look for "connection"; it looks for "low resistance."
  • Standard Limit: Typically < 2 Ohms.
  • Precision Limit: For power circuits, a 4-Wire Kelvin test is required to detect high resistance (e.g., > 0.5 Ohms) caused by a bad crimp or cold solder joint, which a standard continuity buzzer would miss.

Component Polarity

Harnesses often contain embedded passive components (diodes, resistors, capacitors).

• Diode Check: The tester must verify polarity (flow in one direction, block in the other). A reversed diode in a harness can destroy the downstream PCB.
• Resistor Verification: The tester must measure the actual resistance value within tolerance (e.g., 120 Ohm +/- 1%), ensuring the correct component was spliced in.

4.13.2 Isolation/Shorts Testing: The Integrity Check

While Continuity checks "good" connections, Isolation checks for "bad" connections. It ensures that nets intended to be separate are electrically isolated.

• The Mechanism: The tester applies a low voltage (typically 5V to 24V DC) to one net and checks for current leakage to all other nets.
• Shorts Detection: Detects direct shorts caused by solder bridges, stray strands touching adjacent pins, or pinched wires inside a backshell.
• Isolation Threshold: The definition of "Isolated" depends on the spec.
  • Standard: > 20 kOhms (Detects "hard" shorts).
  • High Impedance: > 1 MOhm to 100 MOhms (Detects leakage paths caused by flux residue or moisture).

Process Mandate: The test sequence must be Shorts First, Continuity Second. If a unit has a short, continuity testing is irrelevant.

4.13.3 Hi-Pot (Dielectric Withstand) Testing

High Potential (Hi-Pot) testing is a safety stress test, distinct from standard isolation testing. It applies high voltage to stress the insulation and verify it can withstand over-voltage transients without breaking down.

Mandate: Hi-Pot is mandatory for Class 3 assemblies, high-voltage cables (EV/Solar), and safety-critical medical devices.

Test Parameters

• Test Voltage: Typically defined as 2x Rated Voltage + 1000V. (e.g., a 300V rated wire is tested at 1600V).
• Ramp Time: Voltage is increased gradually (e.g., over 0.5 – 1.0 second) to prevent capacitive inrush currents from falsely tripping the tester.
• Dwell Time:
  • Production: 0.1 to 1.0 second (Flash test).
  • Qualification: 60 seconds to prove insulation robustness.
• Leakage Limit (Trip Point): The maximum allowable current flow through the insulation (e.g., < 1 mA or < 5 mA). If current exceeds this, the insulation has broken down (Arcing/Flashover).

Safety Protocols

Hi-Pot testing introduces lethal voltages to the workstation.

• Interlocks: Test fixtures must use dual-hand start buttons or light curtains to ensure the operator cannot touch the harness during the test cycle.
• Insulated Matting: Workbenches must use ESD/High-Voltage safe mats.

4.13.4 Test Fixturing and Interface Life

The mating connectors on the test fixture are "consumables." Every test cycle wears the plating on the test probe.

• Test-Grade Connectors: Use high-cycle mating connectors (e.g., Gold plated, machined pins) for the fixture interface. Using standard production connectors wears them out quickly, leading to false failures ("Ghost Opens").
• Sacrificial Savers: Use a "Saver Cable" between the expensive tester and the Unit Under Test (UUT). When the connectors wear out, replace the cheap Saver Cable, not the tester interface.
• Spring Probes (Pogo Pins): For high-volume production, replace mating connectors with spring-loaded test blocks that touch the connector face/terminals without engaging the locking mechanism, reducing cycle time and wear.

Final Checklist: Electrical Validation Mandates