Check out a rather unusual phenomenon you can see on your oscilloscope in my latest blog (#14):
Oh, and the probe doesn't have to be shorted either.
Have fun. Dave.
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Got it immediately, because I once worked in lab that had cheap plastic chairs that generated 1cm sparks when you stood up!
-- Dirk http://www.transcendence.me.uk/ - Transcendence UK http://www.theconsensus.org/ - A UK political party http://www.onetribe.me.uk/wordpress/?cat=5 - Our podcasts on weird stuff
When I worked a Century Data we had a problem with our new reel to reel vaccuum column tape drive when ever someone would walk by the drive when it was reading it would get data errors. The problem was that the shield on the cable from the heads to the preamp was grounded on both ends.
Bob
That's usually the best way to ground shields.
John
my
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Hey, is that Chinese take-out I spy?
No. Where?
Dave.
-- ================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/
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On the right. Eh, probably an open box.
Look at a piece of blank paper and you will see what i see on that site. Therefore the mashed and flattened tree wins.
Yep, an open Altronics box! Curiously though the contents were made in Australia and not China - how novel!
Dave.
-- ================================================ Check out my Electronics Engineering Video Blog & Podcast: http://www.alternatezone.com/eevblog/
IIRC head signals mostly went via twisted pair. If they had a shield as well we would certainly not ground them on both sides.
Tony
Back in the old days, they used to generate 1/2" sparks.
Nasty stuff that Bakelite.
Goes nicely with wood cases:
If you set the time base correctly and crunch down on a carrot you will see a complex waveform on the scope. Very difficult to store on a digital scope though. :-) Mike
When I started out with a government run telco and some of the gear was still in nice wooden cases. Over the years I saw pallet loads of test gear consigned to scrap. Loads of bridges, wood cased multimeters and bakelite AVO meters. These things sell for quite a few dollars nowadays - aint hindsight nice!
Lunch pictures?
You *want* large amounts of high-frequency common-mode noise?
John
I always call a probe shorted as in the video an "inductive pickup loop" :-).
Of course, even when a probe isn't shorted it's an inductive pickup loop too.
Tim.
I wonder if you take a picture with a longish shutter speed while eating Doritos if you could capture that.
Depends. With floating transducers and shielded twisted pair, it's best to ground the shield only at the transducer end. That way any capacitive imbalance doesn't produce any currents, because the shield is at the transducer's idea of ground.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 hobbs at electrooptical dot net http://electrooptical.net
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