Cable test extends outside the box.(CABLE/HARNESS TEST)

Cable/harness testers traditionally have checked for shorts and opens in completed wiring assemblies. Hipot capabilities were added to support insulation resistance and dielectric withstand testing up to 1,500 VDC.

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Several related considerations also are influencing today's testers. For example, Karl Sweers, technical marketing manager at DIT-MCO, said, "Lean manufacturing techniques drive the test industry to provide modular and portable test solutions. Systems that can easily be used for testing simple cables or large complex assemblies allow the user flexibility to adapt to everchanging requirements and future test needs."

Also commenting on manufacturing needs, Christopher Strangio from CAMI Research said, "Customers are asking for advanced documentation tools including the capability to automatically assign serial numbers to articles under test and archive test reports in a database for future reference. They want built-in controls for label printers, reporting with graphical display of connectors and wiring, and batch test result logging for statistical reports on article quality, all capabilities included in our new v5 software."

Most of today's cable/harness testers provide functionality beyond simple testing. These features differentiate otherwise similar products and support more complete application solutions. Electrical test capabilities also have changed, and technical tester development continues.

For example, Ken Rockwell, general manager at Cablescan, said that the company's Series 90 machine was developed in part to resolve high interwire capacitance problems experienced with the previous design. As a result of its low sensitivity to capacitive loading, the Series 90 is being used in a number of backplane applications with greater than 20,000 test points.

Because software largely determines the Series 90 characteristics, many customer requests for special functions can be satisfied through software changes. "Like most of our competitors, we can easily add a feature to our PC-based testers within a few days. This may include importing wire-list data from a customer database; storing test results with test date, time, and operator identification; or just changing the way data is displayed and printed," Mr. Rockwell explained.

The comparison chart that accompanies this article lists basic parameters as well as unique features for a number of testers. Although there is a distinction between hipot testers and cable/harness testers, if the hipot instrument can address several circuits through a scanner, it has been included.

The suitability of a particular tester for a given application was summed up by Robert Maccarone, manager of global sales and marketing at CableTest Systems: "The right product to purchase is the one that best meets the requirements and provides the best return on investment. Whether to buy the most economical vs. the most expensive depends on a combination of variables that in the end determine return on investment and possibly improved profitability."

Nevertheless, for some markets, economics is not always the primary concern. A unique test capability based on a NASA patent and developed commercially by Eclypse International is helping the United States military maintain aircraft in Afghanistan and Iraq. The company's hand-held ESP Standing Wave Reflectometer identifies wiring opens and shorts and locates the position of the fault within wiring harnesses in the field.

The instrument was developed by Pedro Medelius, associate program manager and chief scientist with ASRC Aerospace at Kennedy Space Center. As shown in Figure 1, space-shuttle wiring is extensive and complex. To compound the difficulty of locating wiring faults, much of the cabling in the shuttle and conventional aircraft is not easily accessible. The Standing Wave Reflectometer performs a test in four seconds and displays the fault location in alphanumeric characters.

Since the ESP instrument was discussed in a previous EE-Evaluation Engineering article, (1) it has attracted a great deal of interest. Chris Teal, marketing director at Eclypse, noted that the meters have been included in more than 250 battle damage assessment and repair kits for the U.S. Army and Marine Corps. In addition, 100 meters are used in the Army Aviation Logistics School training programs at Fort Eustis, VA. Current plans are to train 1,000 troops per year on use of the ESP Reflectometer. (2)

Low-Voltage Testing

Continuity testing is intended to verify that a wiring harness has been manufactured correctly. Relatively low voltages and currents are involved, and there is little chance that the wiring will be damaged during test. Typically, a current is applied and the resulting voltage compared to preset limits. …

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