Re: O-scope question...

Late at night, by candle light, Rich Grise <rich@xxxxxxxxxxx> penned
this immortal opus:

On Mon, 03 Nov 2008 21:29:21 -0600, Tim Wescott wrote:
On Tue, 04 Nov 2008 12:50:21 +1100, Phil Allison wrote:
"sbrehler"

I am looking to purchase a entry/mid-level O-scope and have been eyeing
a BK precision 2125A (30Mhz, Dual Trace, Analog).

http://www.testequipmentdepot.com/bk-precision/oscilloscopes/2125a.htm?
gclid=CKq61L7h2ZYCFQNvHgodDnLe2w


** Looks much like any other, low cost Asian made scope - except for
the inclusion of delayed sweep.

Like all of them I have seen, there is no mention of a magnetic shield
being fitted to the CRT - this means the trace will wobble or shimmer
if ever you bring an AC supply transformer near the unit. Nearly ALL the
famous brand US or European brand scopes have magnetic ( ie Mu Metal )
shields on the CRT to eliminate this.

Whether this matters to YOU depends on what sort of work you intend
doing and how you like to install the scope on your work bench.

Scopes are very much " horses for courses" and what one user loves
another will just HATE !!

Personally, I cannot bear to use a digital scope.

My 5MHz Heathkit scope has a mu-metal shield.

Or at least it has a shield of something that _looks_ like mu-metal.

Doesn't work for snot, though -- it wiggles all over in the presence of a
magnetic field. I think they just put something in there so it'd _look_
like it had a shield (either that, or there's something special about the
scope that makes it extra sensitive to mag fields, and it'd be tons worse
without the shield -- that's a scary thought).

I have an electric pencil sharpener on my desk next to my CRT monitor. You
should see the screen when I sharpen a pencil!

Cheers!
Rich


Some years ago I needed to adjust the monitor for the supervisory
system. It's inside a kiosk and hard to reach in the normal position.
So I swung it around, facing north, made the adjustments and
de-magged. Swing it back, facing south. Looking at it up front it
looked like ***. I had to pull it back as far as possible and use the
glass window as a mirror to find the de-mag button. Never expected the
Earth field to make such a difference.

- YD.

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