I’m fairly well versed in component labels like C1, R12, U72, etc but while taking apart a small external hard drive I found a component which looks to be made of ceramic labelled SK1.

Now, crystals should be marked as Yx (where x is a number) and both ends seem to terminate at a chip, but is this a standard part label? Other oscillators on the board are labelled as you’d expect.

enter image description here


closed as off-topic by Chris Stratton, Nick Alexeev Oct 7 '18 at 23:13

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  • \$\begingroup\$ Some varistor perhaps? Can you zoom out a bit and follow the trace to the left? \$\endgroup\$ – winny Oct 7 '18 at 16:30
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    \$\begingroup\$ Please see our Component Identification Question Guidelines. As it stands, your question currently does not meet several of the requirements. Please take another picture that's in focus! \$\endgroup\$ – Dave Tweed Oct 7 '18 at 16:36
  • \$\begingroup\$ Thanks folks! I’ve already thrown out the PCB so not much luck. I hadn’t expected to learn exactly what part this is in question, but what part type is denoted by “SK”. Sorry if the photo started a goose chase. For what it’s worth, both leads fed back to the IC through R4 and R53. \$\endgroup\$ – RandomInsano Oct 7 '18 at 16:47
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    \$\begingroup\$ I'm voting to close this question as off-topic because the asker has thrown away the component in question and thus it is not available for further investigation. \$\endgroup\$ – Chris Stratton Oct 7 '18 at 17:14
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    \$\begingroup\$ It's not an identification question. It's a perfectly fine question about PCB layout and best-practices naming. \$\endgroup\$ – pipe Oct 7 '18 at 17:38

while taking apart a small external hard drive I found a component which looks to be made of ceramic labelled SK1

It's a shock sensor used by the hard drive controller (hence the choice of "SK" for the designator makes sense - ShocK).

For example, here is the product page for this type of ceramic-package shock / vibration sensor, made by Murata, containing cantilever-mounted piezo elements:


Quoting from that web page:

Murata shock sensors find use in many computer hard disk drives. They detect impacts - for example, when the storage falls to the floor - in a fraction of a second and prevent read and write errors.

  • \$\begingroup\$ If it is necessary to mount it at a 45 degree angle to allow X and Y shock detection, would there not be a diagonal direction in which it cannot detect shock? \$\endgroup\$ – ζ-- Oct 7 '18 at 18:27
  • \$\begingroup\$ Hmm. Given that some have a “primary inclined angle” of 25 degrees that may help for Z? There is usually an accelerometer somewhere as well. \$\endgroup\$ – RandomInsano Oct 7 '18 at 18:44
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    \$\begingroup\$ @AndreyAkhmetov - As RandomInsano mentioned in his comment following yours, some of these sensors have the internal piezoelectric element oriented at an angle to the X-Y plane, so they are sensitive in the Z-axis too. Also some (typically more expensive) hard drives can have multiple shock sensors in different orientations, for improved sensitivity. So in my experience, no, there isn't a direction in which they can't detect shock. That part of my answer was just trying to explain how one sensor could be sensitive in multiple planes, by having it mounted at an angle as shown in the photo.. \$\endgroup\$ – SamGibson Oct 7 '18 at 19:13
  • \$\begingroup\$ @RandomInsano - Yes, my information is that the chosen sensors have Z-axis senstivity for the reason you mention, with the piezoelectric element angled internally to the X-Y planes. \$\endgroup\$ – SamGibson Oct 7 '18 at 19:16

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