Exposing the True Cost of Test

Equipment price is no longer the biggest variable in the equation.

By Grant Drenkow, Hewlett-Packard Company

What is the true cost of test? The purchase price of the test equipment? Return-on-assets? Cost of a test engineer? Maintenance contracts?

As a major electronics manufacturer, Hewlett-Packard surveyed manufacturing and test managers at its manufacturing sites around the world to see if we could determine the true cost of test. The results may be surprising. Our research showed the cost of test equipment was only 6% of the overall cost of test. Maintaining test systems (13%), developing new test systems (24%), and test operations (57%) made up the bulk of the total cost of test.

What causes these costs and how can you reduce them? Let's start with the test system hardware.

Test Hardware Costs
When purchasing new test systems, test engineers generally begin by finding test equipment whose specifications can handle the requirements of the product to be tested. The selection is made by comparing the performance and prices on equipment from a short list of trusted vendors. If the analysis stops here, 94% of the cost of test is not addressed. Can the selection of test equipment influence the total cost of test? The answer is yes, and here's why.

Development Costs
Tip - Take into account a piece of test equipment's ease-of-use before making a purchase. Test system development costs (24% of the total cost of test) are not always a budgeted item and may get very little attention. Yet development costs can easily be 2-3 times the cost of test equipment. Let's assume a test engineer costs around $50 or $60 per hour when you consider wages, salary, training, benefits, office supplies, and other administrative overhead. Saving $500 on a piece of test equipment is a poor investment if the engineer spends an extra 2 weeks learning how to use it. Saving $2000 on a test system may not be worth it if you have to spend 3 weeks building drivers for the instruments.

Tip - Choose a flexible architecture that can easily adapt to the products that need to be tested.

Your choice of a test system architecture can have an impact on the amount of time it takes to develop the system. It is always a trade-off between highly flexible instruments with built-in intelligence or simple instruments that require considerable computing power to analyze the data. An intelligent instrument may take more time to learn but less time programming while an easy-to-use instrument may require considerable time and effort in software to obtain similar results. In general a flexible test system architecture that can be used for multiple applications saves considerable time. For example, H-P's Loveland manufacturing center uses a generic test station that is replicated and modified (if needed), as new products need to be tested.

Tip - Save development time by using a modular test system architecture or a test system platform.

The time it takes to build a test system is dependent on the type of test equipment. One must figure out the physical mounting of the test equipment in a rack, proper grounding and shielding, adequate cooling, communications and triggering between instruments and computers, and fixturing to the device under test. Test system platforms can also save time because much of the assembly work is complete. A modular architecture like VXI has an advantage because the mechanical, electrical, communication, grounding, shielding, and cooling between instruments are already designed, tested, and guaranteed to work by the VXI standard. Fixturing is quite simple because several vendors already have a mechanical interface that can be easily customized for any device-under-test.

Programming is usually the largest cost in test system development. Since most test engineers select their test instruments before they select their software, a few key questions can insure appropriate test hardware will lead to more productive programming.

• Does the instrument use a standard instrument command language like SCPI (Standard Commands for Programmable Instruments)? Tip - Standard commands save programming and documentation time.
• Does the instrument use a standard instrument driver (like VXIplug&play)? Tip - Instrument drivers make it easy to communicate with the test equipment.
• Does the vendor supply programming examples for the instrument? Tip - Programming examples provide a jump-start in writing the test program.

Careful selection of the test system software is also important to reduce development time.The following questions are quite appropriate in selecting the right software package.

• Is the software easy-to-use? Tip - Graphical programming languages are growing in popularity because they significantly reduce the time spent writing software.
• Is the software "open" to work with other industry-standard software? Tip - Software today must be able to co-exist with other word processing, spreadsheet, and analysis packages.
• Can the software be documented easily? Tip - Once the program is written it must be easily run and de-bugged by other test engineers.

Operations Costs
The largest portion of the cost of test is in operations -- 57%. Operation costs include lights, heat, electricity, operators, test time, and floor space. Test equipment can have an impact on these costs.

The design of the manufacturing floor drives much of the cost in manufacturing. A combination of board test, X-ray, visual inspection, and functional test are used for fault coverage and higher test confidence. Test systems are placed at strategic points in the manufacturing process to insure quality and avoid expensive re-work. If the manufacturing process is complex it makes sense to hire a manufacturing process consultant to help to determine the best test strategy.

Tip - Consider modular test systems when floor space is at a premium. Floor space is an important cost driver, especially in heavily populated areas. If floor space is an issue, the size of the test system becomes an issue as well. A telecommunications company was recently faced with the choice of building a new facility or placing more manufacturing lines in the existing facility. A financial analysis showed that if they could reduce their test equipment from 3 racks down to one they could stay in the existing facility. They chose a VXI-based test system with 3 mainframes in one rack. The resulting savings in floor space paid for the new equipment in the first month.

Tip - Take into account the potential throughput of a test system in high volume applications.

In high volume manufacturing, the speed of the test system plays a role in the number of manufacturing lines required to meet the capacity requirements. A high-speed test system reduces the cost of test by spreading its costs over more units. Floor space is saved because more units can be produced and tested in less space. Revenue increases significantly because more units are being produced, tested, and shipped each month.

Tip - Consider flexible architectures as a means to save on development time for future test systems.

The flexibility of a test system is important in manufacturing facilities where volumes are low but the mix of products can be quite high. Rather than building multiple manufacturing lines each with their own unique test system, a single test system can be used to test multiple products or product variations. Paying a bit more for a flexible test system can actually save in the long run because the number of test systems and manufacturing lines are reduced. One manufacturer of intelligent power supplies used a VXI modular test system so that multiple types of power supplies could be tested with a single system by simply inserting the appropriate VXI cards in the test system.

Maintenance Costs
Tip - If downtime is critical, consider a vendor with local support. Maintenance costs are typically 13% of the total. Maintenance includes support contracts, calibration, repairs, and general maintenance. Support contracts are worth a lot when every hour of downtime is costing your company thousands of dollars in lost production. The cost of a support contract is based on the timeliness of response and the distance of travel required for the repair person. Local service versus regional service can make a big difference and should be considered at the time of purchase. Even stocking extra test equipment is preferable to waiting hours for a repair person and days for repair parts.

Tip - Spend time looking at a calibration strategy and working with a vendor set up for calibration services.

Calibration costs are not always well thought out. An instrument that can be calibrated on site is preferable to one that must be shipped somewhere else for calibration. A vendor who supplies a loaner unit while your unit gets calibrated can save you from expensive downtime. A modular, plug-in instrument saves time because the instrument can be removed, calibrated, and re-inserted very quickly without extensive wiring, cabling, and racking.

Tip - Look for test equipment that can provide some level of preventive maintenance.

Preventive maintenance is usually the best tactic to avoid maintenance costs. Test equipment that monitors its own health and status can be a true benefit. Some types of test equipment (see picture) have built-in displays that provide complete status of the power supply voltages, internal fan speeds, and the plug-in module temperatures as well as warning lights and beepers in case of failure. The fans actually adjust their speed automatically to keep the test equipment at the proper temperatures. The enhanced display also provides histograms and stripcharts of these parameters so test engineers can begin to predict failures even before they happen. The test equipment will warn the operator when the equipment goes outside the preset limits and will shut down the system prior to any potential damage occurring.

How to start?
As a test engineer you will become more valuable if you can see the true cost of the test system through the eyes of the company's CEO. Facilities, production capacity, and people are big cost factors that can actually be influenced by the type of test equipment. Look beyond the specs and price of equipment. Look for ways to reduce floor space with your test equipment by possibly moving to a modular test system. Look at the speed of your test system to increase the number of products that can be tested on a single line. Use a flexible test system to reduce the number of manufacturing lines and the number of operators. Look for test equipment with flexible architectures, standardized command languages, and available drivers. Take into account the support you can get from various vendors including support contracts, calibration services, and local service centers. Look for test equipment that can help you predict failures. Think about downtime as the true cost, not the purchase price of a cheap piece of test equipment.

And of course don't forget the accuracy of the test equipment. You don't want to spend all your time troubleshooting a system that can't keep pace with the products it needs to test.

Hewlett-Packard Company, Measurement Systems Division, Loveland, CO 80537; Tel: 1-800-452-4844.