Tektronix 475 User manual

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TEKTRONIX.
INSTRUCTION MANUAL

WARRANTY
All TEKTRONIX instruments are warranted against
defective materials and workmanship for one year. Any
questions with respect to the warranty should be taken up
with your TEKTRONIX Field Engineer or representative.
All requests for repairs and replacement parts should be
directed to the TEKTRONIX Field Office or representative
in your area. This will assure you the fastest possible
service. Please include the instrument Type Number or Part
Number and Serial Number with all requests for parts or
service.
Specifications and price change privileges reserved.
Copyright © 1972 by Tektronix, Inc., Beaverton, Oregon.
Printed in the United States of America. All rights reserved.
Contents of this publication may not be reproduced in any
form without permission of Tektronix, Inc.
U.S.A. and foreign TEKTRONIX products covered by U.S.
and foreign patents and/or patents pending.
TEKTRONIX is a registered trademark of Tektronix, Inc.
Tektronix, Inc. -® P.O.Box 500 -® Beaverton, Oregon 97005 -® Phone: [phone] -® Cables: Tektronix
070-1333-00
872

TABLE
Introduction
Operating Voltage
Controls And Connectors
Applications
General
Peak-To-Peak Voltage Measurements—AC
Instantaneous Voltage Measurements—DC
Comparison Measurements
Time-Duration Measurements
Frequency Measurement
Risetime Measurements
Time-Difference Measurements
Delayed or Mixed Sweep Time Measurement
Delayed or Mixed Sweep Magnification
Pulse Jitter Measurements
Delayed Trigger Generator
Normal Trigger Generator
Multi-Trace Phase Difference Measurements
High Resolution Phase Measurements
X-Y Phase Measurement
Common-Mode Rejection
Operational Features
General
Intensity Control
Graticule
Vertical Mode of Operation
Deflection Factor
Ground Considerations
OF CONTENTS
Page
1 Input Coupling
1 Trigger Source
3 Trigger Coupling
Trigger Slope
Trigger Level
12 A Sweep Triggered Light
12 A Trigger Mode
14 A Trigger Holdoff
15 Horizontal Mode of Operation
18
Horizontal Sweep Rates
20 Sweep Magnification
20 External Horizontal (X-Y) Operation
21 Output Signals
23 Intensity Modulation
25 Calibrator
28 Obtaining Basic Displays
29 Introduction
30 Normal Sweep Display
30 Magnified Sweep Display
32 Delayed Sweep Displays
33 Mixed Sweep Display
34 X-Y Display
User’s Calibration
35 General
36 TRACE ROTATION Adjustment
36 Vertical GAIN
36 Probe Compensation
38 Basic Timing Accuracy
38 External Horizontal Gain Accuracy
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475 OSCILLOSCOPE
Introduction
This Operators Handbook is intended to give the
necessary information to allow a user to become familiar
with the instrument’s power requirements, functions of
controls and connectors, and also provides a few methods
of making several different measurements of electrical
phenomena. Also included is a rudimentary procedure for
checking basic instrument calibration.
Operating Voltage
This instrument is designed for operation from a
power source with its neutral at or near earth
(ground) potential with a separate safety-earth
conductor. It is not intended for operation from two
phases of a multi-phase system, or across the legs of a
single-phase three-wire system.
This instrument can be operated from either a 115-volt
or a 230-volt nominal line voltage source, 48 to 440 hertz.
The line voltage selector switch in the instrument converts
®
475
the instrument from one nominal operating voltage to the
other. The regulating range selector assembly on the
instrument rear panel selects one of three regulating ranges
for each nominal line voltage, and also contains the line
fuses for overload protection for both nominal line
voltages. To select the correct nominal line voltage and
regulating range, proceed as follows:
1. Disconnect the instrument from the power source.
2. To.convert from 115-volts nominal to 230-volts
nominal line voltage, set the selector switch to the 230 volts
position (toward the rear of the instrument). Change the
line-cord plug to match the power source or use a
115-to-230 volt adapter.
NOTE
Color-coding of the cord conductors is as follows (in
accordance with National Electrical Code):
Line Black
Neutral White
Safety earth (ground) Green

3. To change regulating ranges, loosen the two captive
screws which hold the cover onto the regulating range
selector assembly; then pull to remove the cover.
4. Pull out the range selector switch bar (see Fig. 1).
Slide the bar to the desired position and plug it back in.
Select a range which is centered about the average line
voltage to which the instrument is to be connected (see
Table 1).
115/230V SWITCH INSIDE
Selector switch bar
_ (shown in medium position)
-
IGHT SIDE, REAR)
TABLE 1
Regulating Ranges
Range Selector 15 Se es
Switch Position ce folts 30- folts
Nominal Nominal
LO (switch bar in 99 to 198 to
left holes) 121 volts 242 volts
M (switch bar in 103.5 to 207 to
middle holes) 126.5 volts 253 volts
HI (switch bar in 108 to 216 to
right holes) 132 volts 264 volts
Fig. 1. Power supply regulating range selector.
5. Re-install the cover and tighten the two captive
screws.
®

6. Before applying power to the instrument, check that
the line voltage selector switch and the indicating tabs on
the regulating range selector assembly are in the correct
positions for the line voltage the instrument will be
operated on.
This instrument may be damaged if operated with the
line voltage selector switch or the regulating range
selector assembly set to incorrect positions for the
line voltage applied.
The 475 is designed to be used with a three-wire AC
power system. If a three- to two-wire adapter is used to
connect this instrument to a two-wire AC power system, be
sure to connect the ground lead of the adapter to earth
475
(ground). Failure to complete the ground system may allow
the chassis of this instrument to be elevated above ground
potential and pose a shock hazard.
The feet on the rear panel provide a convenient cord
wrap to store the power cord when not in use.
Controls And Connectors
The major controls and connectors for operation of the
475 are located on the front panel of the instrument.
Several auxiliary functions are provided on the rear panel.
To make full use of the capabilities of this instrument, the
operator should be familiar with the function and use of
each of these controls and connectors. A brief description
of each is given here. Some of the more important
instrument specifications are included here also.
‘

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OSCILLOSCOPE
9)
. CH 1 and CH 2 VOLTS/DIV-—selects the vertical deflection
. VARiable—provides continuously variable uncalibrated deflec-
. UNCALibrated—indicates when the VARiable VOLTS/DIV
. POSITION—positions the display vertically.
. CH 1 OR X and CH 2 OR Y-—input connectors for application
. AC-GND-DC-selects the method used to couple a signal to the
factor in a 1-2-5 sequence (VARiable control must be in the
calibrated detent for the indicated deflection factor). Calibrated
position accuracy is within 3%.
tion factors between the calibrated settings of the VOLTS/DIV
switch.
control is out of the calibrated detent position and the vertical
deflection factor is uncalibrated.
of external signals to the inputs of the vertical amplifier. In the
X-Y mode of operation, the signal connected to the CH 1 OR X
connector provides horizontal deflection and the signal
connected to the CH 2 OR Y connector provides the vertical
deflection. Input impedance is 1 megohm paralleled by approxi-
mately 20 picofarads. Minimum bandwidth in the normal mode
of operation is DC to at least 200 MHz. X-axis has a bandwidth
in X-Y operation of DC to 1 megahertz and is compensated to
have 1° or less phase difference with relation to the Y axis from
DC to 1 MHz.
input of the vertical amplifier. In the AC position, signals are
capacitively coupled to the vertical amplifier. The DC
component of the input signal is blocked. Low frequency
—3 dB point is about 10 Hz. In the GND position, the input of
the vertical amplifier is disconnected from the input connector
and grounded. Allows precharging of the input coupling
capacitor. In the DC position, all components of the input
signal are passed to the input amplifier.
475
®

{ POSITION
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11,
VERTical MODE-selects mode of operation for vertical
amplifier system.
CH 1: Channel 1 only is displayed.
ALTernate: Dual-trace display of the signals of both
channels. Display is switched between channels at the end of
each sweep.
ADD: Signals applied to the CH 1 and CH 2 input
connectors are algebraically added, and the algebraic sum is
displayed on the CRT. The INVERT switch in Channel 2
allows the display to be CH 1 plus CH 2 or CH 1 minus CH
2;
CHOP: Dual-trace display of the signals of both channels.
Display is switched between channels at a repetition rate of
approximately 1 MHz.
CH 2: Channel 2 only is displayed. Must be selected in X-Y
operation.
. 100 MHz or 20 MHz BW/TRIG VIEW—Multi-position switch
that limits the bandwidth of the vertical amplifier system to ap-
proximately 100 MHz or 20 MHz when pulled (100 MHz posi-
tion not provided for SN below B100000) or causes signal con-
nected to A External Input connector to be displayed on the
CRT when pressed. When not pressed, full bandwidth is pro-
vided.
. INVERT —Channel 2 display is inverted in the INVERT (button
in) position.
. BEAM FINDer—comoresses the display to within the graticule
area independently of display position or applied signals and
provides a visible viewing level.
INTENSITY—controls brightness of the CRT display.
@1
475

12.
13.
14,
15.
16.
de
18.
FOCUS —adjusts for optimum display definition.
SCALE ILLUMination—controls graticule illumination.
ASTIGmatism—screwdriver adjustment used in conjunction
with the FOCUS control to obtain a well-defined display. Does
not require readjustment in normal use.
TRACE ROTATION -—adjusts trace to align with the horizontal
graticule lines.
X10 MAGnifier—increases displayed sweep rate by a factor of
10. Extends fastest sweep rate to 1 nanosecond/division.
Calibrated magnified sweep accuracy is typically within 3%.
POSITION-—positions the display horizontally.
CALIBRATOR—a combination current loop/squarewave
voltage output device. Provides a 30 mA (within 2%) square-
wave current, 300 mV (within 1%) squarewave voltage signal
with a repetition rate of approximately 1 kHz.
19. TRIGger MODE-—determines the mode of operation for A
Trigger circuit.
AUTOmatic: The sweep is initiated by the applied trigger
signal. In the absence of an adequate trigger signal, the
sweep free runs and provides a bright reference trace.
NORMal: The sweep is initiated by the applied trigger
signal. In the absence of an adequate trigger signal, there is
no trace.
SING SWP: when this pushbutton is pushed, A Sweep
operates in the single sweep mode. After a sweep is
displayed, further sweeps cannot be presented until the
SING SWP button is pushed.
475

7 ese BooLroyAIGGER SY 20. A TRIGger HOLDOFF-—provides continuous control of time
EVEL between sweeps. Allows triggering on aperiodic signals (such as
complex digital words). In the fully clockwise position (B
ENDS A), A sweep is reset at the end of B sweep to provide the
fastest possible sweep repetition rate for delayed sweep
presentations.
21. COUPLING—determines method used to couple signals to
trigger generator circuit.
AC: Signals are capacitively coupled to the input of the
trigger generator circuit. DC is rejected and signals bDelow
about 60 Hz are attenuated.
LF REJ: Signals are capacitively coupled to the input of the
trigger circuit. DC is rejected and signals below about 5 kHz
are attenuated.
HF REJ: Signals are capacitively coupled to the input of
the trigger circuit. DC is rejected and signals below about
60 Hz and above about 50 kHz are attenuated.
DC: All components of a trigger signal are coupled to the
input of the trigger circuit.
22. SLOPE -selects the slope of the trigger signal which starts the
sweep.
+: Sweep can be triggered from the positive-going portion
of a trigger signal.
—: Sweep can be triggered from the negative-going portion
of a trigger signal.
Pose
POSITION
9
300mv 30mA
“— Goi J 23. LEVEL-—selects the amplitude point on the trigger signal at
which the sweep is triggered.
® 475 7

24. SOURCE-—determines the source of the trigger signal coupled
to the input of the trigger circuit.
NORMal: Trigger source is displayed signal(s).
CH 1: A sample of the signal available in Channel 1 is used
as a trigger signal.
CH 2: A sample of the signal available in Channel 2 is used
as a trigger signal.
LINE (A trigger circuit only): A sample of the power-line
frequency is used as a trigger signal.
EXT: Signals connected to the External Trigger Input
connectors are used for triggering.
EXT = 10 (A trigger circuit only): External trigger signal is
attenuated by a factor of 10.
STARTS AFTER DELAY (B trigger circuit only): B Sweep
runs immediately after the delay time selected by the
DELAY-TIME POSITION dial.
25. External Trigger Input—input connectors for external trigger
signals. Nominal input signal level required for correct trigger
operation is 50 millivolts from DC to approximately 40 MHz
increasing to 250 millivolts at 200 MHz.
26. A AND B TIME/DIV AND DELAY TIME-—A TIME/DIV
switch (clear plastic flange) selects the sweep rate of the A
sweep circuit for A Sweep only operation and selects the basic
delay time (to be multiplied by DELAY TIME POSITION dial
setting) for delayed sweep operation. B TIME/DIV switch
selects sweep rate for the B sweep circuit for delayed sweep
operation only. The VAR control must be in the calibrated
detent for calibrated sweep rates. Calibrated unmagnified sweep
accuracy typically within 2%.
8 475 ®

DELAY TIME POSITION —
9°
27. HORIZontal DISPLAY—determines mode of operation for
horizontal deflection system.
A
“TIME/DIV
ano DELAY TIME
A: Horizontal deflection provided by A Sweep at a sweep
Lp
rate determined by the setting of the A TIME/DIV switch. B
Sweep inoperative.
MIX: First part of the horizontal sweep displayed at a rate
set by the A TIME/DIV switch and the latter part of the
sweep at a rate set by the B TIME/DIV switch. Relative
amounts of the display allocated to each of the two sweep
rates are determined by the setting of the DELAY-TIME
POSITION dial.
A INT: Sweep rate determined by the A TIME/DIV switch.
An intensified portion appears on the display during the B
sweep time. This switch position provides a check of the
duration and position of the B sweep (delayed sweep) with
respect to the delaying sweep (A).
B DLYD: Sweep rate determined by the B TIME/DIV
switch with the delay time determined by the setting of the
DELAY TIME (A TIME/DIV) switch and the DELAY-TIME
POSITION dial.
"CALIBRATOR
® 475 9

DELAY TIME POSITION COUPLING SOURCE B(DLY'D)TRIGGER ‘
° SLorx
ot : , LEVEL
s
+.
28. VARiable—provides continuously variable (uncalibrated) sweep
rates between the calibrated settings of the TIME/DIV switch.
Varies the A Time Base sweep rate in the non-delayed mode of
horizontal operation and the B Time Base sweep rate in the
delayed sweep mode. Extends the slowest sweep rate to at least
1.25 seconds/division. Sweep rate is calibrated when the control
is rotated fully clockwise to the calibrated detent.
29. UNCAL-light that indicates the VAR control is out of the
calibrated detent.
30. X10 MAGnifier—light that indicates the X10 magnifier is on.
31. TRiGgered—light that indicates that A sweep is triggered and
will produce a stable display.
32. READY-—light that indicates A sweep is ‘“‘armed” and, upon
receipt of an adequate trigger signal, will present a single-sweep
display.
33. DELAY-TIME POSITION —provides variable sweep delay from
0.0 to 10.0 times the delay time indicated by the A TIME/DIV
switch.
34. POWER-—turns instrument power on and off.
35. LOW LINE-light that indicates the applied line voltage is
below the lower limit of the regulating range selected by the
Regulating Range Selector assembly.
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A +GATE-—output connector provides a positive-going rectan-
gular pulse coincident with the A sweep time.
B +GATE-—output connector providing a positive-going rectan-
gular pulse coincident with the B sweep time.
. CH 2 VERT SIGNAL OUT-—output connector providing a
sample of the signal applied to the CH 2 input connector.
. EXT Z-AXIS—input connector for intensity modulation of the
CRT display. A 5 volt peak-to-peak signal from DC to 50 MHz
will cause noticeable modulation at normal intensity.
PROBE POWER-—power source foractive probe systems.
@!
475
11

APPLICATIONS
General
The following information describes the procedures and
techniques for making basic measurements with a 475
Oscilloscope. These applications are not described in detail,
since each application must be adapted to the requirements
of the individual measurement. This instrument can also be
used
for many applications which are not described in this
handbook. Contact your local TEKTRONIX Field Office or
representative for assistance in making specific measure-
ments with this instrument. Also, the following books
describe oscilloscope measurement techniques which can be
adapted for use with this instrument.
Czech, J., “Oscilloscope
Springer-Verlag, New York, 1965.
Measuring Techniques’,
Golding, J. H., ‘Measuring Oscilloscope”, Transatlantic,
1971.
Lenk, John D., ‘“‘Handbook of Oscilloscopes’’, Prentice-
Hall, Inc., Englewood Cliffs, N. J., 1968.
Roth, Charles H., “Use of the Oscilloscope’, Prentice-
Hall, Inc., Englewood Cliffs, N. J., 1970.
12
475
Certain portions of the instrument's calibration should
be periodically checked to insure measurement accuracy.
Prior to actually making a measurement, refer to the list of
checks given in the section entitled “‘User’s Calibration’’.
Peak-to-Peak Voltage Measurements—AC
1. Connect the signal to either input connector.
2. Set the VERT MODE switch to display the channel
used.
3. Set the VOLTS/DIV switch to display about five
divisions of the waveform.
4. Set the Input Coupling switch to AC.
NOTE
For low-frequency signals below about 10 hertz, use
the DC position.
5. Set the A Trigger controls to obtain a stable display.
Set the TIME/DIV switch to a position that displays several
cycles of the waveform.
®

6. Turn the vertical POSITION control so the lower
portion of the waveform coincides with one of the graticule
lines below the center horizontal line, and the top of the
waveform is on the viewing area. Move the display with the
horizontal POSITION control, so one of the upper peaks
lies near the center vertical line (see Fig. 2).
7. Measure the divisions of vertical deflection from peak
to peak. Make sure the VAR VOLTS/DIV control is in the
calibrated detent.
NOTE
This technique may also be used to make measure-
ments between two points on the waveform rather
than peak to peak.
8. Multiply the distance measured in step 7 by the
VOLTS/DIV switch setting. Also include the attenuation
factor of the probe, if using a probe that does not have a
scale-factor switching connector.
Example. Assume a peak-to-peak vertical deflection of
4.6 divisions (see Fig. 2) with a VOLTS/DIV switch setting
of .5.
®
475
Using the formula:
Volts setting! VOLTS/DIV
= deflection x :
Peak to Peak ee setting
(divisions)
Substituting the given values:
Volts Peak to Peak = 4.6 X 0.5 V
The peak-to-peak voltage is 2.3 volts.
Position to
center line
\
PTR
Vertical
deflection
Fig. 2. Measuring peak-to-peak voltage of a waveform.
13

Instantaneous Voltage Measurements—DC
1. Connect the signal to either input connector.
2. Set the VERT MODE switch to display the channel
used.
3. Set the VOLTS/DIV switch to display about five
divisions of the waveform.
4. Set the Input Coupling switch to GND.
5. Set the A TRIG MODE switch to AUTO.
6. Position the trace to the bottom line of the graticule
or other reference line. If the voltage to be measured is
negative with respect to ground, position the trace to the
top line of the graticule. Do not move the vertical
POSITION control after this reference line has been
established.
NOTE
To measure a voltage level with respect to a voltage
other than ground, make the following changes in
step 6: Set the input coupling switch to DC and apply
the reference voltage to the input connector. Then
position the trace to the reference line.
14
475
7. Set the input coupling switch to DC. The ground
reference line can be checked at any time by switching to
the GND position.
8. Set the A Trigger controls to obtain a stable display.
Set the TIME/DIV switch to a setting that displays several
cycles of the signal.
9. Measure the distance in divisions between the refer-
ence line and the point on the waveform at which the DC
level is to be measured. For example, in Fig. 3 the
measurement is made between the reference line and point
A.
10. Establish the polarity of the signal. If the waveform
is above the reference line, the voltage is positive; below the
line, negative (when the INVERT switch is pushed in if
using Channel 2).
11. Multiply the distance measured in step 9 by the
VOLTS/DIV switch setting. Include the attenuation factor
of the probe if using a probe that does not have a
scale-factor switching connector.
®

Vertical
distance
Reference line
Fig. 3. Measuring instantaneous DC voltage with respect to a
reference voltage.
Example. Assume that the vertical distance measured is
4.6 divisions (see Fig. 3), the waveform is above the
reference line, and the VOLTS/DIV switch is set to 2.
Using the formula:
Instan- vertical VOLTS/
taneous = distance X_ polarity X DIV
Voltage (divisions) setting
®
475
Substituting the given values:
Instantaneous _ 46X41X2V
Voltage
The instantaneous voltage is +9.2 volts.
Comparison Measurements
In some applications it may be desirable to establish
arbitrary units of measurement other than those indicated
by the VOLTS/DIV switch or TIME/DIV switch. This is
particularly useful when comparing unknown signals to a
reference amplitude or repetition rate. One use for the
comparison-measurement technique is to facilitate calibra-
tion of equipment (e.g., on an assembly-line test) where the
desired amplitude or repetition rate does not produce an
exact number of divisions of deflection. The adjustment
will be easier and more accurate if arbitrary units of
measurement are established so that correct adjustment is
indicated by an exact number of division of deflection.
Arbitrary sweep rates can be useful for comparing harmonic
signals to a fundamental frequency, or for comparing the
repetition rate of the input and output pulses in a digital
count-down circuit. The following procedure describes how
to establish arbitrary units of measure for comparison
measurements. Although the procedure for establishing
vertical and horizontal arbitrary units of measurement is
much the same, both processes are described in detail.
15

Vertical Deflection Factor. To establish an arbitrary
vertical deflection factor based upon a specific reference
amplitude, proceed as follows:
1. Connect the reference signal to the input connector.
Set the TIME/DIV switch to display several cycles of the
signal.
2. Set the VOLTS/DIV switch and the VAR VOLTS/
DIV control to produce a display an exact number of
graticule divisions in amplitude. Do not change the VAR
VOLTS/DIV control after obtaining the desired deflection.
This display can be used as a reference for amplitude
comparison measurements.
3. To establish an arbitrary vertical deflection factor so
the amplitude of an unknown signal can be measured
accurately at any setting of the VOLTS/DIV switch, the
amplitude of the reference signal must be known. If it is
not known, it can be measured before the VAR VOLTS/
DIV control is set in step 2.
4. Divide the amplitude of the reference signal (volts)
by the product of the vertical deflection established in step
2 (divisions) and the setting of the VOLTS/DIV switch.
This is the vertical conversion factor.
16
475
Vertical reference signal amplitude (volts)
Conversion = vertical deflection (divisions) X VOLTS/
Factor DIV switch setting
5. To measure the amplitude of an unknown signal,
disconnect the reference signal and connect the unknown
signal to the INPUT connector. Set the VOLTS/DIV switch
to a setting that provides sufficient vertical deflection to
make an accurate measurement. Do not readjust the VAR
VOLTS/DIV control.
6. Measure the vertical deflection in divisions and
calculate the amplitude of the unknown signal using the
following formula.
VOLTS/DIV
Si vertical vertical
gnel = witch ©. conversion. X deflect!
Amplitude i = . = ton
setting factor (divisions)
Example. Assume a reference signal amplitude of 30
volts, a VOLTS/DIV switch setting of 5, and the VAR
VOLTS/DIV control is adjusted to provide a vertical
deflection of four divisions.
©

Substituting these values in the vertical conversion factor
formula (step 4);
Vertical
Conversion = = 1.5
Factor
Then with a VOLTS/DIV switch setting of 1, the
peak-to-peak amplitude of an unknown signal which
produces a vertical deflection of five divisions can be
determined by using the signal amplitude formula (step 6):
Signal
Amipiivade 1VX 1.5 X 5 = 7.5 volts
Sweep Rates. To establish an arbitrary horizontal sweep
rate based upon a specific reference frequency, proceed as
follows:
1. Connect the reference signal to the input connector.
Set the VOLTS/DIV switch for four or five divisions of
vertical deflection.
2. Set the TIME/DIV switch and the VAR TIME/DIV
control so one cycle of the signal covers an exact number of
®
horizontal divisions. Do not change the VAR TIME/DIV
control after obtaining the desired deflection. This display
can be used as a reference for frequency comparison
measurements.
3. To establish an arbitrary sweep rate so the repetition
rate of an unknown signal can be measured accurately at
any setting of the TIME/DIV switch, the repetition rate of
the reference signal must be known. If it is not known, it
can be measured before the VAR TIME/DIV control is set
in step 2.
4. Divide the repetition rate of the reference signal
(seconds) by the product of the horizontal deflection
established in step 2 (divisions) and the setting of the
TIME/DIV switch. This is the horizontal conversion factor:
Horizontal
Conversion =
Factor
reference signal repetition rate (seconds)
horizontal deflection (divisions) X TIME/DIV switch setting
5. To measure the repetition rate of an unknown signal,
disconnect the reference signal and connect the unknown
signal to the input connector. Set the TIME/DIV switch to
17