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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: RE: Unfortunately... posted by pictureguy on January 14, 2012 at 11:59:04:
"From this I'd conclude the microphic fuse myth busted"
From WHAT? Prey thee show us the data from your wonderous test...
You may be surprised if you actually did the work which is why most of us don't draw conclusions from thought experiments!
"So, now that we've got a vibrating fuse clip....which is firmly attached to the board, we've got a vibrating board? The fundamental of all this is 60hz."
Yes to the first part, no to the second. The fundamental is really 120 Hz unless you are using a half-wave rectifier.
You don't think PCB's vibrate? Stick it in your ear! Here's how:
- tie a foot long thread to one of the corner mounting holes.
- Wrap the other end around your little finger a few times.
- Stick that finger in your ear.
- Tap the board in various places with eraser end of a pencil or just a finger of your other hand.
Isn't that cool? If the boss doesn't catch you you can learn to play the melody and bass line at the same time by tapping the right spots for the melody at each beat. If sticking it in your ear seems crude and the board has any low level analog circuits you can probably extract the same information at their outputs but you may need some additional AF gain. Dies are intrinsically little strain guages and the newer packages provide rather tight coupling mechanically between the chip and the board.
Yes, the resonances are different when the board is screwed down. Just how they change depends largely upon the location of the mounting holes. I've actually had to have the PCB mounting holes moved on some gear to keep case flexure from modulating the offsets of op-amps and showing up as orientation sensitivity to users.
Rick
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Follow Ups
- RE: Unfortunately... - rick_m 19:02:20 01/14/12 (0)
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