Where you find vibe testing, shock usually doesn’t lag far behind. The basic concept of a shock test is simple: pick the drive up, drop it and measure what happens. Of course, accurate results demand accurate test machinery, and Seagate’s labs are meticulous.
One drop we watched exhibited a 600 G amplitude with a one millisecond width on the sine wave pulse. As you may recall from high school physics, if the pulse width gets shorter, such as a half- or even quarter-millisecond, that increases the frequency input, or shock amplitude, to the drive. Think of it this way: if a right hook to your jaw takes two seconds to deliver its force to your face, you’re going to be fine. If it takes a tenth of a second, you’re going to be sprawled on the floor. Features within a hard drive respond differently to different shock pulse widths.
“We have to test the drives at various pulse widths and amplitudes to make sure that we’re good at various frequencies,” explained one tech. “Because if the drive gets shocked out in the field, you're not going to get an exactly perfect pulse input. It depends on what you drop it on. Or if it’s in a system and the system gets shocked, that will change the reaction. We look at the robustness of the product in a controlled fashion at various amplitudes and pulse widths so that we can get a good idea how it will behave out in the field.”
Curiously, to control the pulse width, engineers control some of their drop parameters with these little, circular foam pads. We had to laugh, watching these excruciatingly precise tests run on equipment worth many thousands of dollars, with the key test components being something that look like drink coasters. You know you’re in the presence of die-hard engineers when…