Preface to fifth edition

Preface to fifth edition

Preface to fifth e d i t i o n Keeping this book up to date is r a t h e r like painting Edinburgh's f a m o u s bridge over the Firth of Forth - no s...

148KB Sizes 6 Downloads 154 Views

Preface to fifth e d i t i o n Keeping this book up to date is r a t h e r like painting Edinburgh's f a m o u s bridge over the Firth of Forth - no sooner do t h e y get to the e n d t h a n it's time to start all over again at the beginning. In the same way, no sooner does a n e w edition of this book come out t h a n one or other of the oscilloscopes illustrated or featured will go out of production, usually to be replaced by a later, i m p r o v e d model. A n d as for A p p e n d i x 2, one can m o r e or less g u a r a n t e e that by the time a n e w edition is in the offing, at least 50 per cent of the m a n u f a c t u r e r s or their agents will h a v e c h a n g e d their address or telephone number. As ever, the p e r f o r m a n c e a n d value for m o n e y offered by the c u r r e n t models h a v e a d v a n c e d considerably since the a p p e a r a n c e of the last (fourth) edition. This is a continuing source of mild surprise a n d quiet satisfaction for a n y o n e w h o has b e e n interested in the oscilloscope scene for a n y length of time - w h i c h in m y case a m o u n t s to nigh on fifty years. M y first scope, h o m e built for cheapness of course, was a h o m e b r e w conversion of an ex-RAF Indicator Unit Type 182A, w h i c h incorporated a VCR517C cathode ray tube. The unit was available on the p o s t - w a r military e q u i p m e n t surplus m a r k e t for a few pounds, a lot of m o n e y in those days - especially for a lad still at school. Even so, it was considerably c h e a p e r t h a n units containing the m o r e p o p u l a r VCR97 cathode ray tube, w i t h its shortpersistence green phosphor. So, for reasons of financial stringency, m y first oscilloscope h a d a long persistence cathode ray tube w i t h a blue 'flash' a n d 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 r e m o v e d this, m a k i n g the tube r a t h e r less inappropriate for oscilloscope duty. Nevertheless, the afterglow was always a nuisance except for single shot applications or during e x t e n d e d observation of a stable triggered w a v e f o r m - u n f o r t u nately I n e v e r t h o u g h t of putting a deep blue filter in front of the screen. (A s u b s e q u e n t conversion to TV use was e v e n less

~~

,-'-

,-,,..

~ ~.,

~

~,-. ~ ~

o ~ ~. , ~

~

~ ~ ~~

~ ~

~ ~

~

~ ,-,

2-, ~

g

.

.

~

.

~ . ~

.

.

=.

.

.

~

:~

.

N

,-,_

=

~ >~~

~

.

~ - - ~

~

~ .

~ o

~,

~

~

,.-,

~

~

~

~

8

o ~ ,,--,o

"

s-

~

~

,..., 8

~~

~ ~

,.-,-,

9

~

s

~ s---~ ~

~ ~ ~ ~ ~ > ~ ~ ~ =~ .,2=. ~

~-~ ~ ~ ~.~ .2 ~ ~ ~ o.,~.

~

~ ~~'-' ~ ~ ~ ~"~ ~ 8-3"' ~ ~ ~ ~ - ~ -,.. o ~_ ,_. ~" ~ ~ : ~ ~- ~ ~ ~:'~~ ~-~~ "~ -~ ~ ~ ~ ~ ~ i ~ ~~~

"

~ ~ ~ _.~.

~

Preface to fifth e d i t i o n

xi

available from a n u m b e r of manufacturers. This is no longer the case, so perhaps the logical m o v e might seem to be the omission of the chapter in its entirety. But it has been retained, for a n u m b e r 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 w h i c h all c.r.t.s depend for their operation. Secondly, with the m a r c h of time, sources of information on the m o d u s operandi of storage cathode ray tubes will become rarer and rarer. Thirdly and m o r e importantly, m a n y analogue storage scopes are still in use, a n d some guidance on their advantages, limitations and quirks m a y 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 m a n u f a c t u r e r s still produces analogue storage oscilloscopes, using a 'scan converter tube'. The principle of operation of these is also t o u c h e d 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 n o w 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 m a n u 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 m a n y m a n u f a c t u r e r s and their agents w h o have assisted by providing information on, and pictures of, their products. F r o m 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 u p o n which I have d r a w n freely in Chapters 6 and 11 and elsewhere, and for other valued assistance. I.H.

October 2000