Key Takeaways (Executive Summary)
- The Baseline: Every professional cable assembly must undergo 100% Continuity Testing to ensure no wires are crossed (mis-pinned) or broken (open circuit).
- Safety First: For cables carrying power (>50V), Hipot (High Potential) testing is mandatory to check for insulation breakdown and potential arc faults.
- Destructive Testing: Pull Force Testing is a mechanical check performed on crimps during setup. It is destructive, so it is done on samples, not the final product.
- The "Golden Sample": Always require a First Article Inspection (FAI) report to validate that the manufacturing process matches the print before mass production begins.
Trust, But Verify
In manufacturing, there is a saying: "You cannot inspect quality into a product; you have to build it in."
However, in the world of wire harnesses, verification is the only firewall between a safe product and a recall. A technician might crimp 99 terminals perfectly, but if the 100th terminal has a stray strand of copper touching the signal line, the entire system fails.
To prevent this, we employ a multi-layered testing protocol. It’s not just about "does it work?"; it’s about "will it last?"
Here are the standard tests you should expect your manufacturer to perform.
1. Continuity Testing (The Logic Check)
This is the standard, non-negotiable test for every single unit (100% Testing). We use automated testers (like Cirris or CableEye systems) to verify the internal map of the cable.
What it Checks:
- Opens: Is the wire broken internally?
- Shorts: Are two wires accidentally touching?
- Mis-wires: Did the operator swap Pin 1 and Pin 2?
- How it works: The tester sends a low voltage (5V) signal down every pin and ensures it arrives at the correct destination. If the resistance is too high (e.g., >2 Ohms), it fails.
2. Hipot Testing (The Safety Check)
Hipot (High Potential) testing, also known as Dielectric Withstand, is a stress test for the insulation. It is critical for cables carrying dangerous voltages (medical, EV, industrial).
The Concept: Just because two wires aren't touching doesn't mean they are safe. If the insulation is thin or nicked, high voltage can "jump" (arc) between them.
- The Test: We apply a massive over-voltage (e.g., 500V DC or 1000V AC) between the conductors for a few milliseconds.
- The Pass Criteria: If any current leaks through the insulation (Leakage Current), the cable fails. This ensures the customer won't get shocked.
Comparison Table: Continuity vs. Hipot
Do you need both?
|
Feature |
Continuity Test |
Hipot Test (Dielectric) |
|---|---|---|
|
Voltage Used |
Low (5V - 12V) |
High (500V - 1500V+) |
|
Goal |
Verify Logic / Connection |
Verify Safety / Insulation |
|
Detects |
Broken wires, Crossed pins |
Nicked insulation, Arcing risk |
|
Standard |
Mandatory for all cables |
Mandatory for Power/HV cables |
|
Cost |
Included in assembly cost |
Adds setup time/cost |
3. Pull Force Testing (The Mechanical Check)
Crimp quality is invisible to the naked eye. A crimp can look perfect but fall off if you tug on it.
Pull Testing is a Destructive Test. We cannot do it on the finished cable (because it breaks the part!).
- Process: Before the shift begins, the operator crimps 5 sample terminals.
- Action: We put them in a Pull Tester machine that stretches them until they snap.
- Validation: If the wire breaks before the crimp slips, the crimp is good. If the wire pulls out of the crimp, the pressure is too low. We re-calibrate the press and re-test.
Standard: We follow UL 486A pull force requirements.
- 18 AWG Wire: Must hold 20 lbs (89N).
- 12 AWG Wire: Must hold 70 lbs (311N).
4. Advanced Testing: VSWR (RF Cables)
For coaxial cables (antennas, Wi-Fi, GPS), simple continuity isn't enough. We need to know how well the signal travels.
We use a Network Analyzer to measure VSWR (Voltage Standing Wave Ratio).
- The Concept: If the connector is soldered poorly, the radio signal bounces back (reflects) like an echo.
- The Goal: We want a VSWR close to 1:1 (No reflection). A high VSWR means the cable is absorbing the signal, and your range will suffer.
Frequently Asked Questions (FAQ)
Q: Do you test 100% of the cables or just a sample? A: For Continuity and Short testing, we test 100% of cables. We never ship a "dead" cable. For destructive tests (Pull Test) or advanced RF validation, we typically test based on an AQL (Acceptable Quality Limit) sampling plan, such as checking 1 unit every 500.
Q: What is a "Golden Sample"? A: A Golden Sample is a confirmed, working cable kept at the testing station. Before testing the daily batch, the operator plugs in the Golden Sample to verify the tester itself is working correctly.
Q: Can Hipot testing damage the cable? A: No. It is a non-destructive test if the cable is good. If the cable has a defect, the high voltage will burn through the weak spot, revealing the failure—which is exactly what we want to happen in the factory, not in the field.
