No other ATE class comes in as many sizes and price variations as cable/harness testers. Sizes range from cigar-box shapes to multirack floor models and prices range from less than a few hundred dollars to as much as $100,000.
Obviously, features differ—from low pin-count opens/shorts test support to systems with high-voltage, leakage and capacitive tests for thousands of terminations as well as detailed defect-location diagnoses. Some systems merely generate error logs or provide pass/fail indications—and that may be all you need for some applications. Others perform comprehensive analysis and recommend process changes.
But one aspect shared by most of today’s cable/harness test systems is the personal computer (PC). PCs are being used in many different ways, mainly depending on the applications.
The term “PC-based” can be interpreted in different ways so definitions are helpful here. “PC-based systems are only those that depend on a PC for operation and cannot function without it,” noted Christopher Strangio, director of marketing at CAMI Research. “Many test instruments upload/download information to and from PCs but these are truly stand-alone systems and not directly controlled by a PC. As such, they do not qualify as PC-based.”
Stand-alone equipment may be controlled through a built-in PC or microprocessor. “Most stand-alone wiring/harness testers use an embedded onboard microprocessor to control the system and execute required functions,” Mr. Strangio continued. “Such systems usually are self-contained and furnished with function-dedicated switches, indicators and numeric displays comprising a nonstandardized user interface.”
Most microprocessor-controlled cable/harness testers include an I/O port for communicating with a PC. Typical systems of this type are the Dynalab Circuit Analyzers which feature an RS-232 communications link, the Cirris Signature 1000+ which functions as a stand-alone or as a PC-based unit, and the Invotronics HDT-500 Tester/Director which operates in one of three modes.
The HDT-500 can be programmed by downloading the data into the tester/director through the PC’s printer port, by an RS-232 link from the PC or by a small hand-held battery-operated microprocessor/memory system called the Dataporter. “These methodologies provide options to suit specific applications, said Joseph De Santo, president of Invotronics. “The printer-port download is simple but the computer or the tester must be mobile. The RS-232 link sounds great but requires hard- wiring. The third option, the Dataporter, transfers bidirectional data without a dedicated PC or fixed wiring. The only limitation—someone physically hand-carries the data.”
Advantages of the microprocessor-controlled stand-alone units include low cost, minimal space and excellent suitability for operation on factory floors. “Most of the environments this equipment operates in could be troublesome for disk drives, monitors and keyboards,” said Gary James, president of Dynalab. “For that reason, we use LCDs or vacuum fluorescent displays, battery-backed RAM and PCMCIA type cards to avoid the problems posed by mechanical data-storage devices.”
Testers With Embedded PCs
Cirris, Cabletest International and Palomar are among the companies offering benchtop testers with embedded PCs. At Palomar, the embedded computer is only used in the test control unit while the user interface is furnished through an external PC. Advantages cited by Frank Piracci, manager FACT® Systems at Palomar, include the cost savings and flexibility provided by an off-the-shelf PC motherboard and standard PC software.
The embedded PC in Cabletest’s portable Horizon tester not only controls the hardware but also supports a simple user interface provided by a built-in touch screen. The internal PC also performs all the data-base management and error-processing functions.
“In this case, the PC and the software, in effect, become the tester,” said Mike Mathews, director sales and marketing at Cabletest International. “The marriage of the standard PC with standard software and test hardware makes the system much more capable and flexible. Better error diagnostics can be performed and more accurate measurements can be made.”
No systems can be more PC-based than those with control electronics residing in the PC on a PC-plug-in board. This type of architecture is typified by systems offered by CheckSum and Eclypse.
This solution offers several advantages, according to Brian Laine, founder and sales and support manager at CheckSum:
It uses the PC’s backplane and power supply.
High performance is achieved since the test hardware is directly controlled by the PC bus.
Since test software is directly controlled by a PC software package, integration with other off-the-shelf software tools (editors, translators, networks) is easy.
The Eclypse analyzer data interface is a single half-sized controller card placed in one PC slot and an I/O card. “Communication is provided through a balanced line interface based on the RS-422 protocol,” explained Christopher Teal, marketing director/systems engineer at Eclypse International.
“This type of interface communicates over large distances with low signal loss and high EMI immunity. This allows placing the PC and controller terminal several hundred feet from the instrumentation which, in turn, facilitates connection to large assemblies, such as aircraft harnesses,” Mr. Teal concluded.
But besides these plug-in board controlled PC-based systems, many other configurations are tied to the PC via a standard port or a plug-in interface board. CAMI’s CableEye series, for instance, is a PC-based tester with an assembly containing data acquisition circuits plus an integrated test fixture linked to the computer via the serial port. User input occurs through menus on the PC or by a push button that triggers a user-defined automatic test sequence. Pass/fail results are indicated by LEDs and a tone, while diagnostic information is shown on the PC screen.
DIT-MCO International’s equipment interfaces with a stand-alone PC via the enhanced parallel port (EPP). The EPP port delivers excellent throughput so the interface does not create a bottleneck and you can achieve high test speeds. The tester can be used as a manufacturing tool, not just as an isolated test system.
“As an integrated component in manufacturing, our test systems connect to corporate networks and mainframes,” Ralph Taylor, director of engineering at DIT-MCO said. “The benefits include:
Central control of test data.
Download of engineering/manufacturing information (CAD data and wire lists) to speed up test-program preparation.
Speedy test results/error information analysis to facilitate statistical process control.
A graphical error information display for troubleshooting, repairing and improving product design and manufacturing processes.
Integration with handlers for automated production.
“A PC interface offers yet another option: a remote-control test station. A wireless laptop acts as the test station, so you see what is occurring when testing large assemblies in aircraft or vehicles. No longer must you come back to the computer to see instructions or error information. Instead of requiring two people to communicate with intercoms or headphones, you can check or change switch settings while viewing needed information right on a wireless laptop,” Mr. Taylor concluded.
There are still other ways to interconnect the PC with the test system and benefit from the many innate PC capabilities. Palomar includes IEEE 488 cards in the user-interface PC as well as in the test system to control and interchange information. Cabletest uses the PC as a controller and data-base manager in its PC-based MPT Wiring Analyzer Systems. “We operate in a DOS or Windows environment and have a software architecture so you can build your own interface and error-reporting functions,” remarked Mr. Mathews. “This is very helpful in highly automated environments where special software or special menus may be required.”
Satisfying Test Requirements
So how much testing is really necessary? First you must decide what are the limits that constitute under-testing and over-testing. Avoiding under-testing normally is not too difficult since minimum test levels are frequently specified by your customer or a regulatory agency. Over-testing, happens more often, particularly when allowing for contingencies that may never occur, when applying test limits based on habit, or when the test equipment has more capabilities than needed for the product at hand.
Performing tests that are more stringent than the product specification or application demands is becoming more prevalent, said Brent Stringham, sales/marketing manager at Cirris Systems. For example, test capabilities, such as hipot, resistance and component measurements previously available only in high-cost testers, are now included in testers costing less than $5,000.
And sometimes when test specifications have not been provided, it is not clear what voltage levels should be applied and what insulation resistance or leakage current tests should be performed. “This confusion often leads to over-testing or applying the maximum levels the test equipment supports, which may be much more stringent than necessary for a particular cable,” commented Mr. Stringham. “Fortunately, some testers now analyze an assembly and recommend test settings, simplifying the test setup, avoiding over-testing and enhancing productivity.”
Many generic test specifications are broad enough to accommodate future harness/cable applications. “For example, a harness is tested for dielectric strength of 1,000 VDC although it will carry only a 5-V data stream. Later, a 24-V line is added to this harness to accommodate expanded product usage and the 1,000-VDC test is still more than adequate,” said Mr. Teal.
The extent of such an expanded test application may be questionable. “Just because a harness tester can apply 1,000 V or 1,500 VDC does not imply that this is the best voltage to test with, Mr. Teal continued. “In some cases, testing at 1,500 VDC can even harm the product. Each aspect of a harness must be considered, such as wire and connector ratings and the ultimate harness usage environment, before settling on a set of test specifications.”
Many commercial cables and harnesses, especially those used for data communications, may never carry signals exceeding 24 V and high-voltage tests may be unwarranted. This, however, is not the case for most aerospace and military applications.
“Safety is a principal issue in the aerospace industry,” said Mr. Piracci. “Detection of dielectric breakdown, flash-over and potential arcing between conductors has become an important issue for our customers. The most requested test requirement is for dielectric breakdown detection, typically performed at 1,000 to 1,500 VAC/VDC.
Cable/Harness Test Products
Software Simplifies Program
Preparation, Interface Design
Windows-based TestEdit™ and TestAssistant™ simplify test-program preparation and interface design for DIT-MCOs test systems. TestEdit includes the test file editor and the address correspondence editor (ACE). A cross-check facility compares address correspondence tables (ACT) and test files to detect missing commands or UUT definitions. UUT and test data may be displayed simultaneously. TestAssistant, using a connector information library, automates interface cabling design and generates ACT files. Add-on software includes a wiring graphics analyzer, an automatic program generator and an errorlog data-base generator. Call company for price. DIT-MCO International, (800) 821-3487.
Datalogging Feature Supports
ISO 9000 Documentation
New software for the CableEye® PC-based tester adds datalogging and export/import functions. Datalogging provides batch-test documentation for ISO 9000-certified firms. Test results include a line-item error report, automatic serialized label printing, a total and average test time report, and a percent-accuracy indicator. The optional export/import utility translates CableEye’s internal indexed data base into comma-delimited ASCII text. Cable files from other testers or from CAD programs may be imported. System: from $895; export/import utility: $95. CAMI Research, (800) 776-0414.
System Provides Production
Guidance, Performs Tests
The HDT-500 Tester/Director combines production guidance and post-production test features. Used in conjunction with the company’s Lighted Termination Modules, operators are guided by LED indicator lights to each termination point. Errors are prevented since the operator cannot perform a new termination unless the previous one is correct. Program preparation is simplified via the learn mode or with a computer interface and the company’s HM™ software. The HDT tests for opens, shorts and erroneous resistance values. From $1,099. Invotronics, (800) 521-3579.
Circuit Analyzers Feature
Range of Test Facilities
The Model 501 and 1502 Circuit Analyzers feature a modular design to accommodate diverse testing needs. They handle 128 to 128,000 test points and achieve test speeds of up to 3,500 tests/min. Both models have programmable drive, and measurement and limit levels ranging from 25 mV to 500 VDC or 350 VAC, 5 mA to 2.5 A and 0.01 W to 1,000 MW . Capacitance is measured from 1 nF to 99.9 µF. The 1502 also provides an optional hipot test facility from 100 VDC to 1,500 VDC. <$30,000. Eclypse International, (909) 947-8839.
Wiring Tester Includes
3,000-V Option, LabView Support
The MPT Series Wiring Analyzers include the rolling-cabinet-mounted MPT1000 (10,000 points), the benchtop MPT5000 (3,200 points), the portable/19″ rack-mountable MPT5000L (1,600 points) and the suitcase-mounted distributed-architecture-based MPT5000D. Switch modules range from 500 VDC to 3,000 VDC/2,500 VAC, and types can be mixed within the same system. Test programs may be generated from known- good products, entered via language statements, created automatically from data bases, wiring lists or CAD/CAM data, and translated from existing files. Call company for price. Cabletest International, (905) 475-2607.
Pentium PC Tester Features
VGA Touch-Screen Interface
The Signature Touch 1 Cable/Harness Tester is Pentium PC-based and tests complex assemblies with up to 512 points containing resistors, diodes, capacitors and twisted pairs. It identifies which end of a cable has an open or short. Resistance ranges extend from 0.1 W to 100 kW , test voltages from 5 VDC to 1,000 VDC and insulation resistance from 5 MW to 1 GW . Test data includes the number of good/bad assemblies, and measurement and specific error information. 128 points: $5,495. Cirris Systems, (800) 441-9910.
Expands to 1,536 Points
In its basic configuration, the Model 1536 Circuit Analyzer features 128 bidirectional test points. It expands to 1,536 points by inserting plug-in I/O boards. PC-based PASS®Dynalab, (614) 866-9999. software provides a menu-driven test-programming environment. Test voltage extends from 2 to 12 V, thresholds 0 to 10 V and constant current load from 40 µA to 10 mA. An RS-232-C port, internal battery backup, and a control port for activating external devices are provided. 1,152-point system: from $2,621.
Plug-in Modules Plus Software
Convert PC Into Test System
The R-90 Continuity Test System checks cables, harnesses, backplanes and printed circuit cards. The system provides 200 test points per PC plug-in module and expands to 3,200 test points. It self-learns a known-good assembly and saves the connection data on disk. Alternatively, you can enter test specifications from engineering data. The system performs high-speed tests on the assembly, reporting any opens or shorts. Reports show the failure data using DUT location identification. Test system: $995; expansion module: $895. CheckSum, (360) 435-5510.
High-Voltage Wiring Analyzer
Is Easy to Use, Flexible
The FACT Series 7000/8000 High-Voltage Wiring Analyzers are Windows-based, and feature an automatic test program generation software package and a template-driven test program editor. The minimum number of test points is 60, expandable to 3,600 (Model 7000) or 54,000 (Model 8000). Each system performs a range of continuity, leakage and capacitive tests. Options include a touch-screen monitor, a bar code reader and various IEEE 488-controlled instruments. Starting at $75,000. Palomar Products, (619) 931-3622.
Backplane Tester Uses
High Pin-Count Cards
The Lintest Backplane Tester uses multiple high pin-count switching cards, each accommodating up to 784 pins. The switching cards may be plugged directly into the backplane-under-test. They also may be mounted in cassettes and inserted manually using a special tool or automatically by pneumatic cylinders. Switching cards are interconnected by a special bus, minimizing the need for external cabling. Call company for price. Testpro, 011 47 22 72 48 60.
Copyright 1997 Nelson Publishing Inc.