Everyone would like the testing process to be a painless experience, but often problems arise that can delay testing and maybe even the product's schedule. Sometimes equipment fails a portion of a test. Sometimes the product may self-destruct. Sometimes communications get crossed between the manufacturer and the test lab. Proper planning and preparation for each project can prevent such problems and ensure a productive and successful visit. This article presents an overview of how to prepare for the visit. See the checklist in the sidebar "Emissions/Immunity Lab Visit Checklist" below.

The lab needs to know about a product and its intended market to determine what standards apply and what testing is required. Gone are the simple days of only having to determine whether to test to FCC Class A or Class B. Depending on the product, it can now take hours to determine which standards, or what parts of those standards, apply. For example, to market an RF transmitter in Europe, the R&TTE Directive, the EMC Directive, and the Low Voltage Directive could all apply.

Identifying the appropriate standard can involve examining hundreds of them to determine which are required for a specific product. More research will then be needed to identify which parts of the selected standards apply. The test lab must also determine whether the type of transmitter and its frequency of operation are harmonized within each member state of the European Union. With this information, the test lab can inform the manufacturer—before coming in for the actual testing process—of any special requirements.

Some of the key information that the test lab needs to know includes:

• Power and frequency requirements.
• Clock and processor speeds.
• Input/output (I/O) connections and cables used.
• Number of possible configurations.
• Peripheral equipment needed.
• Support equipment required for proper operation.
• Intended geographic market.
• Size and weight of equipment.

This product information helps the test lab determine not only the tests required, but also the configurations in which the product should be tested. To ensure proper testing, it is imperative that the lab knows what the product is and what it does. This information enables the lab to determine the time needed for testing and to plan accordingly.

Before scheduling the visit, manufacturers should understand how the product will be tested. If multiple configurations exist for a product, it may need to be tested to identify the worst-case condition. Devices must be tested in the configuration that causes the worst-case condition, and this configuration may not be the same for immunity as it is for emissions. For example, a device such as a computer modem may have an option of using various types of communication ports, but not necessarily at the same time. Two ports could be provided to enable both a dial-up connection and a cable connection. Testing must be done with each port being used separately and in combination to determine the highest risk for emissions or immunity, depending on the test.

Some test labs use a questionnaire to obtain pertinent information from the manufacturer. The answers are used to help determine an appropriate test plan. A test plan will include the test standards that need to be run for that particular device. The plan will also define the specific test conditions. It is usually best to run potentially destructive tests last.

A test plan should include a list of tests such as the examples shown in Tables I–III. These tables list the applicable tests and requirements for a printer, which falls under the category of information technology equipment. The tables show the tests that would be necessary for CE marking the device for sale in the European Union. In this case, emissions tests would probably be run first, and ESD and surge testing would be done last.

It is beneficial for manufacturers to complete such an information sheet before taking a product to the lab for testing. This information helps the test lab understand the product. Often, pertinent information from this form is used directly in the test report. To avoid errors, it is important to print legibly or type the information on the form.

The client is responsible for providing all necessary information prior to the report being written. Some information should be provided even before the testing is done. Failure to provide this information can delay the testing schedule and the issuing of the report, which would likely result in the product not getting to market in the intended window.

Always provide a model number and not just a product name. Product names often change by the time products are ready to market. If a name does change, the test report could include the wrong model number erroneously. Such an error could cause delays in issuing the report and, therefore, in product launch.

After providing all necessary information, a few other factors should be considered before testing begins. Before transporting the system to the lab, set it up one last time to make sure it functions properly. Often a product can be mailed or shipped to a test lab for testing, rather than having someone from the manufacturer available on-site.

When a product is shipped, provide the lab with names and phone numbers of individuals to contact if problems or questions arise. Contacts should be available during working hours to avoid wasted time by having the test engineer waiting for an answer to a question. However, for devices that are complicated or difficult to operate, it is crucial for a person knowledgeable with the product to be present during testing. Whether the manufacturer chooses to be present throughout testing or opts to check in periodically, it is essential that manufacturers talk regularly with the laboratory engineer to ensure that the process runs smoothly.

Certainly, everyone hopes that the equipment under test (EUT) will breeze through the tests without any problems and that no failures or out-of-spec conditions will arise. For manufacturers whose products do not experience problems, congratulations are in order. They can sit back and let the test engineer do all the work. But sometimes, failure conditions do show up during the testing process.

When at the lab to monitor testing, the company's representative should be prepared by having components and supplies available to address the problems. Before scheduling testing, determine what services and supplies the lab makes available. A good lab will have an EMC engineer present. In addition, labs often have common components such as filters, conductive gasketing, capacitors, chokes, fuses, and conductive materials to facilitate necessary changes to a product. Manufacturers can sometimes request that the test engineer or EMC engineer make the change. In these cases, it is essential that a representative from the manufacturer monitor the alteration to ensure that it is replicated in production.

Mark Rozema tests a product with electrostatic discharge.

If the product is small and samples are easily available, it is wise to bring an extra one or two samples along. Some tests, specifically in areas related to RF immunity, can be destructive to equipment. For some tests, the product must be subjected to 8 kV of electrostatic discharge. Other tests subject products to voltage interruptions and surges. Power supplies may be subjected to simulated lightning strikes. These tests often cause nonrecoverable failures. Such failures may destroy the test sample, which can set production plans back by days or weeks. It is particularly frustrating if travel time to the lab takes several hours or more. Bringing extra parts and supplies can minimize any downtime.

Typical extra parts include a power supply, fuses, metal-oxide varistors (MOVs), circuit boards, special or unique cables, and system software. It is important to bring schematics as well. The test engineer must thoroughly understand a product when RF troubleshooting. Schematics provide key product data for the troubleshooting process. Because test standards require that products be tested as complete systems, it is essential to bring all peripherals, cables, tools, and software that the device needs to operate normally.