Cossor Instruments COSSORSCOPES User manual
MANUAL
FOR
COSSORSCOPES
Model
2000
,.,
AND
Model
2100
COnlinuous developmenl
may
result in minor changes to design.
COSSOR
INSTRUMENTS LIMITED
The Instrument Company
of
the Cossor Group: a subsidiary
of
the Raythe01! Company, U.
S.A
.
COSSOR
HOUSE
.
HIGHBURY
GROVE
LONDON,
N.S
ENGLAND
Telephone:
CANonbury
1234 (IS lines)
Cables:
Cossor,
London,
N.S
Telegrams:
Cossor,
Norphone.
London
Code:
"Bentley's
Second
"
lNST
.P.601
CONTENTS
Page
INTRODUCTION
l
SPECIFICA
TION
2
INSTRUCTIONS
FOR
USING
MODEL
2000 and
MODEL
2100 4
Power Supply 4
Controls-Initial
Setting 4
Calibration
of
Y Amplifiers 5
Input
to
Y Amplifiers 5
Time-base Controls 5
Intensity Modulation 7
Illuminated Graticule 7
Measurements 8
Delay 8
CIRCUIT
DESCRIPTION
FOR
MODEL
2000
13
Power Supply
13
Pre-amplifiers
14
Main Amplifier
14
Time-base
15
Bright-up and 20 Mc/s Generator
17
Calibrator
18
CIRCUIT
DESCRIPTION
FOR
MODEL
2100
19
Power Supply
19
Pre-amplifiers
20
Main Amplifier
20
Time
-base
21
..,
Bright-up and
20
Mc
/s Generator
23
CaJibrator
24
SERVICING
FOR
MODEL
2000 and
MODEL
2100
25
Initial Setting
of
Controls
25
Power Supply
25
Preliminary Adjustments
25
X Amplifier
26
Time-base Linearity
27
Time
CaJibration
27
20
Mc/s Marker
27
Externai Brightness Modulation
27
De1ay
28
Trigger System
28
y Amplifiers
28
Amplifier Transient Response
29
Pre-amplifier Transient Response
29
Amplifier Frequency Response
29
Attenuators
29
Amplifier
Input
Capacity
29
Volta
ge
Readings for Model 2000 30
Voltage Readings for Model 2100
32
CIRCUIT
COMPONENTS
FOR
MODEL
2000
50
CIRCUIT
COMPONENTS
FOR
MODEL
2100
61
-
MECHANICAL
ITEM
S
FOR
MODELS
2000 and 2100 72
SPARES
AND
SERVICE
74
ILLUSTRA
TIONS
Fig.
Fig. 2
...
Fig. 3
Fig. 4
Fig. 5
Fig. 6
l Fig. 7
Fig. 8
....
I Fig. 9
Fig.
10
Fig.
11
Fig.12
Fig.
13
Fig.
14
Fig.
15
Fig.
16
Fig.
17
Fig.
18
Fig.
19
Fig.20
Page
Block Schematic Diagram
of
Mode1 2000
10
Block Schematic Diagram
of
Mode1 2100
12
Left-hand Side View
of
Mode1 2000
34
En1arged View
of
Yl
Amplifier Circuit (Mode1 2000)
35
Right-hand Side View
of
Mode1 2000
36
En1arged View
of
Y2 Amplifier Circuit (Mode1 2000)
37
Top
View
of
Mode1 2000 38
En1arged View
of
E.H.T.
Circuit & Bright-up and
20
Mc/s Generator
Circuit (Mode1 2000) 38
Bottom View
of
Mode1 2000
39
Enlarged View
of
Time-base Circuit (Trig. Amplifier) Mode1 2000 40
Enlarged View
of
Time-base Circuit (X Amplifier) Mode1 2000
41
Left-hand Side View
of
Mode12l00
42
En1arged View
of
Yl
Amp1ifier Circuit (Mode1 2100)
43
Right-hand Side View
of
Mode1
2100 44
En1arged View
of
Y2 Amp1ifier Circuit (Mode1 2100)
45
Top
View
of
Mode1 2100 46
En1arged View
of
E.H.
T.
Circuit & Bright-up and
20
Mc/s Generator
Circuit (Model 2100) 46
Bottom View
of
Mode1 2100
47
En1arged View
of
Time-base Circuit (Trig. Amplifier) Mode1 2100
48
Enlarged View
of
Time-base Circuit (X Amplifier) Mode1 2100
49
Circuit Diagram
of
YI Amplifier (Model 2000)
Circuit Diagram
of
Y2
Amplifier (Mode1 2000)
Circuit Diagram
of
Power Supp1ies (Mode1 2000)
Circuit Diagram
of
Time-base (Mode1 2000)
Circuit Diagram
of
YI Amp1ifier (Mode1 2100)
Circuit Diagram
of
Y2
Amplifier (Mode1 2100)
Circuit Diagram
of
Power Supp1ies (Mode1 2100)
Circuit Diagram
of
Time-base (Mode1 2100)
,..
...,
....
INTRODUCTION
Models 2000 and 2100 are compact versatile oscilloscopes for general-purpose measurements.
Physically, the two instruments are almost identical and the circuitry for each Model
is
very similar.
Both Models employ a modern double-gun
CRT
which provides a brilliant display with excellent
definition.
The
CRT
for Model 2100, however,
is
fitted with a spiral post-defiexion anode and
is
operated at a higher voltage so that faster writing speeds can be attained than with Mode! 2000.
With this
CRT,
the bandwidth
of
Model 2100
is
also increased over that
of
Model 2000 by approx-
imately I
Mc
/s.
Two
identical amplifiers with built-in pre-amplifiers are provided for Y defiexion.
The
triggering system provides four modes
of
operation, Auto, Slow, Fast and
TV
Frame.
In
the
Auto mode, the scan will lock automatically
to
a diverse range
of
waveforms, manual adjustment
of
the
TRIG.-LEVEL
controI being unnecessary. A
TRIG
.-REP. potentiometer controls the
trigger threshold
ofthe
calibrated time-base and perrnits it to free-run
if
desired.
In
the other modes,
the waveform voltage leve!, at which the time-base will commence to scan, can be set by the
TRIG
.-
LEVEL
controI. Triggering can be selected on either the rising or the falling curve
of
the waveform in
all modes and from
EXT,
y I and
50
~.
A sync. separator enables a composite
TV
waveform to
be locked to a line or frame pulse.
Four
overlapping ranges
of
time-base delay are available.
A d.
c.
coupled X amplifier
of
variable gain provides calibrated sweep expansion on all time ranges,
and, alternative!y, may be used to amplify externaI signals. An Intensity Mod. switch se!ects
internally generated
50
mfLsec
markers or externaI Z-modulation signals.
The
graticule can be
illuminated, and the illumination can be changed from normal to red simply by rotating the
graticule through 90 deg. Both Model 2000 and Mode! 2100 can be fitted with standard Cossor
cameras.
CATHODE-RAy
TUBE
Yl
AMPLIFIER
Y2
AMPLIFIER
Y PRE-AMPLIFIERS
(two)
TIME-BASE
TRIGGER
SPECIFICA
TIO
N
4 in. (10 cm) double-gun tube with green f1uorescence, operating
at 1·5
kV
for Mode12000 and at 4
kV
for Mode1 2100. Blue or long
afterglow tubes available to special order. Individual
BRIGHT-
NESS
and
FOCUS
controls provided for each beam. -
Frequency response d.c. to 5
Mc
/s for Mode1 2000 and d.c. to
6
Mc
/s for Mode1 2100, better than
30
% down.
Rise-time 70 m
fL
sec for Model 2000, 60 m
fL
sec for Mode1 2100.
Output
def1exion not less than 6 cm.
Sensitivity calibrated100 mY/cm to
100
V/cm,in steps
of!,
3 and
10.
Variable 3 : l on each range.
Input
Attenuator impedance l
MQ,
30
pF
on all ranges.
Identical with
Yl
amplifier.
Sensitivity. l mY/cm, bandwidth
lO
c/s to 200 kc/s, and
10
mY/cm,
bandwidth 5 c/s to l Mc/s, better than
30
% down.
Input
impedance l
MQ.
In
normal operation, positive
input
signals def1ect both traces
upwards.
21
calibrated ranges from 3 sec/
cm
to l
fL
sec/cm.
Sweep expansion X
10.
Effective1y d.c. coupled bright-up pulse to
CRT
grid gives uniform
brightness along the trace length and sweep bright-up on all ranges.
Four modes
of
operation, Auto, Slow, Fast and
TV
Frame. Positive
or negative from
50
c/s, internai or externa!.
Adjustable
TRIG
.
-LEVEL
and
TRIG.-REP
. controls permit
initiation
of
scan from any part
of
the waveform. Range
of
leve1
controi ±
30
V for externaI signals.
Sensitivity. InternaI 3
mm
def1exion.
ExternaI
0·1
V.
2
X AMPLIFIER
-CALIBRATION
GENERAL
POWER SUPPLY
SIZE AND WEIGHT
OPTIONAL EXTRA
Delay.
Four
overlapping ranges cover 4
fLsec
to 2·5 msec (extendable
to
50
msec).
Variable controi DELAY
FINE
is
uncalibrated.
D.C.
to l
Mc
/s, 30% down. Variable sensitivity 0·5 V/cm to 2 V/cm.
Voltage.
By
internally generated waveform switched through the
amplifier. Accuracy
within·
3%. When
input
attenuator
is
accurately set on 0·1 V/cm range, ranges 0·3 V/cm to
100
V/cm
are within ±5%.
Time. Directly calibrated in time/cm, accuracy within ± 5% on
basic ranges.
High-frequency time marker.
50
mfLsec
(±
3%) intensity
modulation for accurate measurement
of
pulse rise-time.
Synchronized to time-base.
Illuminated graticule with variable control.
Externai Z-modulation terminal.
Direct access to Y plates.
Sweep saw-tooth (100
V)
available at front panel.
Fittings for attachment
of
Camera Model J428 or Mode! 1458.
Mains
110
Vand
220 V, with taps ± 5
V,
±
10
V, and ±
20
V.
Frequency
50
c/s to 60 c/
s.
Consumption J00 W (approx.).
Height
15
in. (38,1 cm).
Depth
17
lll.
(43'2 cm).
Width
II
lll.
(27,9 cm).
Weight
34·5lb
(J
5·7 kg).
Probe Model 2005 (for Yl and
Y2
amplifiers
).
Input
Impedance
10
MO,
9 pF.
Attenuation X
10.
3
INSTRUCTIONS
FOR
USING
MODEl
2000
AND
MODEl
2100
POWER
SUPPL
y
Warning
Do not touch any part
of
the circuit while the mains supply
is
connected to the instrument.
The
mains fuse
is
in the unswitched side
of
the mains supply and will be "
live"
when
the supply
is
connected, even though the instrument
is
switched
off.
Ensure that the mains voltage selector at the rear
of
the instrument
is
positioned correctly for the
mains supply from which the Cossorscope
is
to be operated.
With the instrument Mains switch in the off position (up), connect the mains supply
to
the
Cossorscope.
CONTROLS
-INITIAL
SETTING
Position the controls
as
stated below: -
BRIGHTNESS
and
FOCUS
mid-position
of
trave!.
Trig
.-Selector +
Yl.
Trig.-System
AUTO.
TRIG.-REP.
fuUy
clockwise.
Delay Range
OFF.
Time/cm
10
msec.
TIME
MULTIPLlER
x
1.
Yl and
Y2
SHIFT
mid-position
of
trave!.
Yl
and
Y2
V/cm
·1
V/cm -
A.C.-D.C.-CAL.
(Yl and
Y2
) CAL.
Intensity Mod.
NORMAL.
X
SHIFT
mid-position
of
trave!.
Switch on the Cossorscope and ensure that the name-plate
is
illuminated. Rotate the
TRIG.-REP.
controI in a counter-clockwise direction until the time-base locks, that is, just past the point where
free-running ceases.
Note
Usually when the sweep speed
is
changed, readjustment
of
the
TRIG.-REP.
controI
is
not
necessary.
Using the displayed square wave adjust the
BRIGHTNESS
and
FOCUS
controls for optimum
....
spot geometry, and use the
SHIFT
controI to position
the
traces
as
desired.
4
...
Do
not allow the white line, which
is
marked on each
BRIGHTNESS
control, to appear in front
of
the escutcheon, except when using externai signals via the X amplifier to the X plates. With
externai signals so applied, advance the
BRIGHTNESS
controls because no internai bright-up
pulse
is
applied to the grids
of
the
CRT.
For
normal operation, set the Yl
SHIFT
controi (on the left-hand side) to position one trace in the
bottom half
of
the
CRT
screen and set the Y2
SHIFT
controi (on the right-hand side)
to
position
the other trace in the top half
of
the
CRT
screen.
CALlBRATION OF Y AMPLIFlERS
On each Y channel, adjust the Y
GAIN
(SET
CAL.) controi
so
that the displayed square wave
(50 c/s for Model 2000 and a nominal I kc/s for Model 2100), which
is
internally pre-set to
O·
3 V
peak-to-peak, has an amplitude
of
3 cm.
To
calibrate the pre-amplifiers, turn the
Yl
and
Y2
V/cm switches to the required pre-amplifier
position, that is, to
·01
V/cm or ·
001
V/cm, and adjust the Y
GAIN
(SET
CAL.) controls so that
the displayed square wave has an amplitude
of
3 cm.
Do
this separately for each pre-amplifier
sensitivity position.
Whenever the Y
GAIN
(SET
CAL.) controls are moved from their calibration settings or a pre-
amplifier
is
switched in or
out
of
circuit, re-calibrate the Y amplifiers,
as
described above,
beJare
making measurements.
INPUT TO Y AMPLIFlERS
Do not apply any
input
above 500 V to either
of
the Y amplifiers.
If
the d.c. path
(l
M.o)
to
earth
through the attenuator
is
likely to cause interference
to
the apparatus that
is
being tested,
put
the
A.C.-D.C.-CAL. switches to the A.C. position.
To
terminate an
input
to the coaxial socket
of
the amplifiers, connect aresistor, value
50
n less than
....
the terminating value required, between the Y input terminal (maroon) and the earth terminal (black).
When the terminating value required
is
50
n,
connect the
Yl
and Y2
INPUT
terminals direct to the
EARTH
terminals because the
50
n
is
connected internally,
as
indicated on the escutcheon
of
the
instrument.
When using the ·
001
V/cm range, uniess the signal source
is
of
low impedance, connect the input
lead via a screened coaxial input socket and screen the 4 mm
input
terminal with the adapter provided.
....
TIME-BASE CONTROLS
Trig.-System
Five-position switch for selection
of
four modes
of
operation:
AUTO;
SLOW;
FAST;
TV
FRAME.
The
fifth position
EXT.TB
is
used for defiecting the trace horizontally with externai signals.
A
UTO:
easiest mode to use and suitable for general-purpose
working.
In
the absence
of
a trigger signal, time-base free-runs
at a maximum repetition rate
of
100 c/s.
The
sweep locks auto-
....
matically to a trigger signal, the P.
R.F
. increasing with the amplitude
of
the applied signal. Preferred mode when it
is
required to lock
to
sine waves in the frequency range
of
l Mc/s
to
5 Mc/
s.
N.B.
The
TRIG.-LEVEL
controi
is
inoperative in this mode.
5
Time
/
cm
Multiplier
X
S81FT
X EXPANSION
SLOW:
in this mode, with the
TRIG.-REP.
control set correctly,
the time-base will not trigger unless a trigger signal
is
applied.
The
exact part
of
the signal to trigger the time-base can be seleeted
by
using the Trig.-Selector switch and the
TRIG.-LEVEL
control.
FAST:
for stable triggering from high-frequency and fast rise-
time waveforms with unwanted low-frequency signals present, for
example, square-wave ed
ge
with
50
e/s ripple. Selection
of
part
of
the signal for triggering
is
made by using the Trig.-Selector switch
and
TRIG.-LEVEL
control.
TV
FRAME: introduces a sync. separator into the circuit.
The
TRIG.-LEVEL
control may then be used to eliminate the video
signal and the sync. separator removes the line pulse from a
composite
TV
signal. Time-base
is
triggered from
TV
Frame
pulse or low-frequency signal with high-frequencies present.
N.B.
The
minimum amplitude
of
the
TV
signal for correct
triggering
is
3 cm
(l
cm sync. only).
EXT.
TB
: position enabling use
as
an X input terminal to be made
of
the
EXT
.
TB
IN
/
INT.TB
OUT
terminal, which
is
located at
the bottom right-hand side
of
the front panel and at which the
time-base waveform appears in the other four positions
of
the
Trig.-System switch. Can be used, for example, for driving
frequency-swept oscillators.
To
stop the time-base when using this position,
tum
the
TRIG.-
REP. control fully counter-clockwise.
Seven-position switch for selection
of
sweep speeds: l see/cm,
100
msec/cm,
10
msec/cm, l msec/cm,
100
iJ.sec
/cm,
10
iJ.sec/cm,
l
iJ.sec
/cm.
Three-position switch multiplying all 7 sweep speeds, seleeted by
the Time/cm switch, by factors
of
l,
2 or
3.
Used for horizontal positioning
of
the traces, clockwise rotation
of
the control giving movement to the right and counter-clockwise
rotation giving movement to the left. Sufficient control
is
a\'ailable
to move any part
of
the trace to the centre
of
the
CRT
screen.
Variable control calibrated ex
l,
x
10)
at each end
of
travel,
clockwise rotation causing expansion of the displayed waveform
about the centre
of
the
CRT
screen.
...
....
...
6
Delay
Range
T
rig.-Selector
TRIG.-LEVEL
TRIG.-REP.
Five-position switch:
OFF,
and
four delay positions,
1,
2, 3 and 4
(maximum) introducing delay between
the
triggering signal and
the
start
of
the time-base.
When
the
switch
is
in one
of
the delay
positions,
AUTO
mode should
not
be used.
For
delay, adjust
the
TRIG.-REP.
controI correctly,
as
described
above (Controls
-Initial
Setting),
and
rotate the
TRIG.-LEVEL
control fully counter-clockwise.
Then
turn
the
TRIG.-LEVEL
controI clockwise until the time-base triggers.
Six-position switch for selection
of
the signal source from which
it
is
desired to trigger the time-base. Switch positions are in three
pairs:
EXT.
The
signal applied to the
EXT.
TRIGGER
terminal
(bottom left-hand side).
y
1.
The
signal applied to the YI amplifier.
50~.
The
mains supply waveform.
Each pair perrnits triggering either from
the
positive-going (marked
+ ) or from
the
negative-going (marked -) edge
of
the signal.
Used to select the position on the triggering signal at which
triggering will occur
and
is inoperative in the
AUTO
mode.
For
triggering during negative leveIs, position the control to
the
left.
For
triggering during positive leveIs, position the controI to the
right.
The
smaller
the
trigger signal, the nearer to the central
position will the controI be set.
See
"Delay
Range"
above for use
of
this controI when using
delay ranges.
Allows the time-base to operate
In
a triggered or free-running
condition.
INTENSITY MODULATION
The
Inten
sity Mod. switch has three positions:
NORMAL Traces brightened during
the
sweep period only.
...
20 Mc/s As for
NORMAL
,
but
modified by a 20
Mc
/s sine wave, which
is
synchronized to
the
time-base to provide 50
mfl.sec
marker pips
along
the
traces.
Used for measuring
fa
st rise-times and for accurate time measure-
ment, generally at the
fa
stest sweep speed.
EXT.
Used
for brightening
the
traces when
an
externaI waveform is applied
to the intensity modulation terminal fitted to the back panel
of
the
instrument.
The
terminal
is
a.c. coupled through a cathode-
follower to
the
grids
of
the
CR
T.
7
ILLUMINATED
GRA
TICULE
The
graticule can be illurninated
by
using the
GRATICULE
controi (top left-hand side
),
clockwise
rotation increasing the illumination.
Graticule rotation, which assists in normal measurement work, also provides white or red illumination
as
desired. Red
is
especially advantageous when using a visor
to
observe a faint trace, because it
will not affect the dark adaptation
of
the eye.
Changing the illumination from white
to
red, or vice versa,
is
achieved by rotating the graticule
. through 90 deg.
MEASUREMENTS
Before making any voltage measurements, position the A.C.-D.C.-CAL. switches to CAL. and, with
the attenuators switched to ·l V/cm, or
·01
V/cm, or
·001
V/cm according to the sensitivity required,
set the Y
GAIN
(
SET
CAL.) controls
so
that the display on the
CRT
bas an amplitude
of
3 cm,
calibration on the
·1
V/cm range holding good for all ranges
·1
V/cm to
100
V/
cm
. For example,
switch the sensitivity to
10
V/cm, then
if
the trace height
is
4·3 cm, the amplitude
is
43
V peak-to-peak.
When only one Yamplifier
is
used, do not position the
A.C.-D.C.-CAL.
switch to CAL. for theother
amplifier, since the
50
c/s calibration waveform may be picked up by the amplifier in use.
For time measurements, always put the X
EXPANSION
controi to one
of
the calibrated positions,
that is, X I or X
10.
For example, with the Time/cm switch positioned at
100
fLsec
/cm, and
Multiplier at X 2, then
if
the trace occupies 3·5 cm, the duration will be 700
fLsec
when the
X
EXPANSION
control
is
position at X J, or
70
fLsec
when the X expansion
is
X
10.
When using the X
10
position with the
Time
/cm switch positioned at I flsec/cm, use
20
Mc
/s
markers for high accuracy because at this maximum sweep speed, the sweep Jinearity does not
perrnit measurements
to
be made accurately off the graticule.
..,
DELAY
For
convenient examination
of
short puJses or fast edges, use the delay facility to delay the start
of
the time-base by a time slightly less than that represented by P.R.F.
of
the pulse, thus enabling the
whole
of
the next pulse, including the start, to be displayed. For example,
if
a pulse
of
l
flsec
and
repetition rate
50
kc
/s
is
being examined,
put
the Time/cm switch to I
fLsec,
the Delay Range switch
to position 2 and adjust the
DELA
Y
FINE
controi
so
that the puJse succeeding the synchronizing
puJse appears on the
CRT
screen.
For more detailed examination, adjust the X
EXPANSION
control in conjunction with the Delay
controis.
When the setting
of
either the Delay Range switch or the
DELA
Y
FINE
controi
is
altered, readjust
the
TRIG.-LEVEL
controi
as
necessary.
Longer periods
of
delay may be obtained by increasing the value
of
C410 at the rate
of
0·004
fLF
for each I ms
ec
of
delay required, for example, to increase the delay to
50
msec, increase C410 to
...
0·2 flF.
8
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2
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