Protection Test Standards

When technology works, a television displays the desired TV program, a cell phone completes a call, or a DVD plays regardless of the brand of DVD player, it is adherence to Engineering Standards that allows this to happen. There are standards to specify the dimensions of integrated circuit packages, the voltage levels and signals for a computer monitor, and how to perform a drop test of a portable device. The number of standards and standards bodies can be bewildering, but following standards has many benefits. Not only do products from different manufacturers work together, but products cost less. Standardized components can be used by many manufacturers, reducing cost. Standards are developed under the umbrella of a standards body. Experts from interested parties meet to determine the best way to do something. The interested parties include manufacturers and users of products, manufacturers of test equipment, and sometimes members of regulatory bodies from local, regional or national governments. An important class of standards test for the ability of electrical systems to survive electrical stress.

The electrical stresses that systems experience are quite varied. They range from ESD events with nanosecond rise times and 10s of amps of current to lightning with micro second rise times and 10s of thousands of amps of current. Testing products to every conceivable real world stress is unrealistic. Instead standards bodies develop a limited number of standard tests, each to address a specific threat. The standards specify stresses in terms of current and voltage waveforms. The most common stress waveform is the double exponential shown in Figure 1 . Typically voltage waveforms are specified into an open and current waveforms are specified into a short. Common waveform parameters are peak voltage and current, rise time (often 10 to 90 % of peak) and a decay time to 50% of the peak. The standards also specify how the stress waveforms are to be applied to the equipment being tested and the criteria for passing or failing each test. This assures that the test results can be reproduced by anyone performing the test, and that systems passing the test can be expected to perform reliably in service.

Figure 1 Double Exponential Waveform

Electronic systems need to work in a wide variety of environments and reliability requirements differ widely by application. It is therefore not surprising that a number of standards bodies have developed to cover specific industries, each with standards for specific threats. The following table lists a number of relevant standards. Links in the table lead to more detailed descriptions of individual standards.

Table 1 Electrical stress standards (hyperlinks give additional information on select standards)

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