April 1997
STAR*TEcH
waves. Keep in mind that the
clock speed only limits how of-
ten a signal can occur, not how
long it lasts. Even slow circuits
can generate very narrow pulses.
The more narrow a pulse, the
higher its equivalent frequency.
It takes a lot of bandwidth to dis-
play these waveforms without
rounding them off at the comers.
tal scopes are not for the begin-
ner. They do a lot of things very
well, but they also have idiosyn-
crasies that require some under-
standing. Get a good analog
scope, then consider the digital
later in your career when you
need what it does.
Whatever you buy, if you buy
new, expect to spend at least
$500-600. In fact, $1200 or so will
really buy you a lot of 'scope
these days, but you can save a lot
of money buy shopping for a
used 'scope. There are quite a few
used test gear companies and sur-
plus houses to chose from. $500
buys a lot there.
f course
wetook
at logic
boc,:rd signals.
That is probably
the mostde-
mandlt1g of our
appUc'ations.
Even so, we
qon' t reaU'y'
need an e)d:ra
tanc'y' 'scope.
Getwhotyou
need, don't go
nuts.
That said, it is also true that when
we look at a digital signal most
of the time we are merely check-
ing for its presence, whether it
crosses the logic thresholds, and
if it shows contention on a line.
My 35MHz B&K has served me
well for over 15 years, but the
100MHz model really does show
me more. Even a 20MHz 'scope
will cover most of your needs,
and it will teach you how to use
a 'scope. Buy as much bandwidth
as you can afford.
Some of the military equivalent
models are just like the commer-
cial 'scopes except they are "rug-
gedized" and often repackaged
for portability and protection.
Check 'em out.
Next Up: m continue with 'Adding
to the Bench': An in-depth look at
troubleshooting equipment essential
for the coin-op service bench.
A couple other things to consider.
Digital? Storage? I say that digi-
power
supply
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