Preface to fifth edition
Keeping this book up to date is rather like painting Edinburgh's
famous bridge over the Firth of Forth - no sooner do they get to the
end than it's time to start all over again at the beginning. In the
same way, no sooner does a new edition of this book come out than
one or other of the oscilloscopes illustrated or featured will go out
of production, usually to be replaced by a later, improved model.
And as for Appendix 2, one can more or less guarantee that by the
time a new edition is in the offing, at least 50 per cent of the
manufacturers or their agents will have changed their address or
telephone number.
As ever, the performance and value for money offered by the
current models have advanced considerably since the appearance
of the last (fourth) edition. This is a continuing source of mild
surprise and quiet satisfaction for anyone who has been interested
in the oscilloscope scene for any length of time - which in my case
amounts to nigh on fifty years.
My first scope, home built for cheapness of course, was a home-
brew conversion of an ex-RAF Indicator Unit Type 182A, which
incorporated a VCR517C cathode ray tube. The unit was available
on the post-war military equipment surplus market for a few
pounds, a lot of money in those days - especially for a lad still at
school. Even so, it was considerably cheaper than units containing
the more popular VCR97 cathode ray tube, with its short-
persistence green phosphor. So, for reasons of financial stringency,
my first oscilloscope had a long persistence cathode ray tube with a
blue 'flash' and yellow 'afterglow'. In its original role as a radar
display, a glass filter tinted deep yellow in front of the screen
suppressed the flash, but I removed this, making the tube rather
less inappropriate for oscilloscope duty. Nevertheless, the afterglow
was always a nuisance except for single shot applications or during
extended observation of a stable triggered waveform- unfortu-
nately I never thought of putting a deep blue filter in front of the
screen. (A subsequent conversion to TV use was even less
x
Preface
to
fifth
edition
satisfactory. Apart from blurred lips.
the
newsreader was
not
too
bad but
a
football match was a disaster. The blue ball with its
long
curved yellow tail looked like a
comet,
and when thc camera
panned from onc end
of thc ground to the ot.her, confusion reigned
supreme.)
A scopc with a long-persist.erice
screen
is
still very
~i~cf~il
in
certain applications, where
it
can
form
;1
very much cheaper oplion
than a variable-persistence storage
oscilloscope
or a
DSO
(digital
storage oscilloscope)
of
similar bandwidth. Oscilloscopcs offcring
the
option
of
a cathode ray tube with
a
long-pcrsistcnce screen in
place
of
a standard one are by now unobtainable, but many long-
persistence scopes are still in regular use. Thus in the world of the
oscilloscope, the old and the new both continue to be useful, each
in its appropriate sphere.
Another example
of
this is the ‘second user market’, an area of
steadily growing importance. As Government Departments and
Agencies and large firms re-equip themselves with the latest and
best in oscilloscopes, large quantities of used but perfectly
serviceable equipment are released.
Most
of this finds its way
onto
he
second user market, where dealcI-s specializing
in
this trade
offer
it
for
resale.
The
riiore
reputable dealers will have
had
the
cquip~icnl ovcrha
ulc~l
and rccalibrated
to
good-as-new condition,
dnd
it
thcn represents cxccllcnt
vnluc
for
thc
srnallrr
company,
the
indcpendcnt
consullaill
and
wen thc
kccn
clcctronics cnthusias~.,
Iri
!his
way, an cxccllcnt oscilloscope,
sprct
i-iini
analyser
or other
instrumcnt (adtnillcdly
of
a
rnodcl
often
no
1ongc.t.
it1
production)
can be obtained
lor
somewhere
betwccii
a
tc.n~h and
a
fifth
of
the
price
of
its current new equivalun1.
The
major
manufacturers
continue
to
support
such instrumcnts
for
some eight
to
ten years
after
the model was
discontinued.
So
a bargain scope can be
repaired
and
maintained as necessary, giving many years of faithful
servicc., especially
if
returned
to
the
maker
for
a
complete overhaul
j
list
before
the period of support expires.
This
filth
edition
of
the
hook,
which was lirst published in
1981
and
has
never been
out
of
print since,
ha
been extensively revised.
Chapter
11,
describing how storage cathode ray tubes work, has
been retained.
It
was added at the third edition when ’analogue’
storage
scopes (i.e. those
using
direct-view
storage
c.r.t.s)
were
Preface to fifth edition xi
available from a number of manufacturers. This is no longer the
case, so perhaps the logical move might seem to be the omission of
the chapter in its entirety. But it has been retained, for a number of
reasons. Firstly, the description of the operation of storage c.r.t.s
illustrates some interesting aspects of electron optics, a branch of
physics on which all c.r.t.s depend for their operation. Secondly,
with the march of time, sources of information on the modus
operandi of storage cathode ray tubes will become rarer and rarer.
Thirdly and more importantly, many analogue storage scopes are
still in use, and some guidance on their advantages, limitations and
quirks may not come amiss. And while oscilloscopes using a storage
cathode ray tube no longer seem to be available (except on the
second user market), one of the major oscilloscope manufacturers
still produces analogue storage oscilloscopes, using a 'scan
converter tube'. The principle of operation of these is also touched
on in Chapter 11. The chapter has therefore been retained, but
with the substantial pruning carried out at the previous (fourth)
edition, while still covering all the fundamentals of the subject.
The book now includes photographs of later models of some of
the instruments which were illustrated in the fourth edition, plus
details and photographs of instruments from various manu-
facturers whose product lines were not previously represented in
these pages, whilst illustrations of models no longer available have,
with but one or two exceptions, been removed.
The author gratefully acknowledges the many manufacturers
and their agents who have assisted by providing information on,
and pictures of, their products. From these, a selection of
photographs has been included illustrating real-time oscilloscopes,
both storage and non-storage, sampling and digital storage
oscilloscopes and their accessories. In each case, the caption at least
gives brief details of the performance of the instrument, whilst in
several cases it has been possible to give a more extensive account
of its performance in the text. My special thanks are due to
Tektronix UK Ltd for providing material upon which I have drawn
freely in Chapters 6 and 11 and elsewhere, and for other valued
assistance.
I.H.
October 2000
~ v
An
advanced
orcillowrpc
of
the
1940s.
Thc
Cossor
niodcl
1035
Mkl
1A
was
a true
dual
beam oscilloscope with
a
~~iaxirii~~iii bandwidth of
7
MHr
(Y
I
amplifier),
100
kHz
jY2
anqilifirrj
and
a
fasrcst
sweep rate
of
15
p
per scan,
with
repetitive,
triggered and single-stroke operation (courtesy
Coscor
Electronics
Lid)
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