Sound Technology 1710A Operating manual

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SOUND
TECHNOLOGY
MODEL
1710A
OPERATOR AND
SERV~CE
MA
UAL
1400
Dell Avenue, Campbell.California
95008
U.S.A.,
TEL
:
(4081378-6540,
TELEX:
357445,
FAX
:
(408)
378-6847

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AfTE -NTION
PLEASE SAVE THIS SHIPPING
CARTON AND ALL
PACKING MATE-
RIALS. THEY HAVE BEEN SPECIFI-
CALLY DESIGNED
TO PROTECT
YOUR SOUND TECHNOLOGY
INSTRUMENT.
IF, AT ANY TIME, YOU HAVE
REASON TO TRANSPORT YOUR
EQUIPMENT, USING THIS CARTON
WILL HELP PREVENT DAMAGE.
NEW CARTONS AND
PACKING
MATERIALS ARE AVAi LAB LE AT A
NOMINAL CHARGE FROM SOUND
TECHNOLOGY.

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SOUND TECHNOLOGY
1400 DELL AVENUE
CAMPBELL. CALIFORNIA 95008
Telephone: [phone]
Telex : 357445
-I
1700 SERIES METER ZERO ADJUSTMENT
The meter is correctly zeroed w~~n the pointer rests directly
over the zero calibration mark on the meter scale. IMPORTANT:
if the meter is not proper(j,.i . iiroed, calibration accuracy will be
affected. To set met er ZJ!Wt: ,~ ~ , ·
a. Turn on unit. ~ ,~t ~) B,RPT swi-tch: to : 300 VOLTS (lOOv for
1710A) and FUNCrION .~ S.,W..iich to VOttS/POWER. (Make sure
Analyzer Select bu~~~ is out for 1710A).
b. BALANCED INPUT terminals should be shorted together and
grounded
to chassis ground.
c. Rotate meter zero adjustment screw (located just below
meter on front panel) until p9inter moves up scale when
turned cw and down scale when turned ccw. Turn screw cw
or ccw until pointer rests directly over the zero
calibration mark, then back off screw a very slight
amount in the opposite direction to relieve tension on
the pointer while maintaining · the zero calibration.
Repeat adjustment if necessar y.
If you have any questions, p1ease c~ntact Sound Technology
Customer
Service at [phone].

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SOUND TECHNOLOGY
1400 Dell Avenue
Campbell, CA 95008
Tel : [phone]
Telex : 357445
5- T 1700 Series U.S. Patents:
3940715, 3 9781101, 4032857 .
a nual Part Numb er: 7900 -00 11
•
Manual printed in U. S.A .
Copyright Marc:h 1979
Pr ice : $ 20 . 00
SOUND TECHNOLOGY
MODEL 1710A
DISTORTION MEAS~REMENT
SYSTEM

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WARRANTY
All new Sound Technology products are warranted aga i ns t defects in materi als
and workmanship for two year~ from the date of delivery . Any instrument or
component that is found to be defective within the warranty period after exami-
nation by Sound Technology or '. an , author i zed representative thereof will be
repaired or replaced without c~arge for labor or material. No o ther warranty
is e,cpressed or implied. We are not liable for consequential damages .
Before returning a product .to S9Und Technology for service , authorization
must be obtained from the factory . For products not covered by the warr a nty .
a purchase order should be forwarded to avoid unnecessary delay . Please
include instrument model number and serial number with all requests for
parts or service to facilitate the fastest poss i ble response .
All
products returned to the fact9"y must be shipped prepaid . For produ c ts
under warranty , Sound Technology will pay for shipment back to the customer .
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SECTION
I
1-
1.
1-2.
1-3.
1-4.
1-5.
1-11.
1-12.
1-B.
1-14.
1-17.
SECTION
II
2-l.
2-2.
2-16.
2-22.
TABLE
OF
CONTENTS
-
OPERATION
. . . . . . . .
SCOPE
OF
SECTION
...
.
INTRODUCTION
.....
.
INPUT
POWER
REQUIREMENTS
POWER
CABLE
. . . . . . .
CONTROLS
AND
INDICATORS.
1-6.
AC
Input
...
..
. '
1-7. Sine
Wave
Generator
.......
.
..
.
1-8. Total Hanronic Distortion
(THO)
Analyzer.
1-9.
Auto
Set
Level
. . . .
.........
.
1-10. Intenoodulation Distortion
(IMO)
Analyzer
TEST
SETUP
....
POWER
CONr~ECTIONS
.
r,ROUND
CONNECTIONS.
SIGNAL
CONNECTIONS.
1-15. Generator.
1-16. Analyzer.
OPERATING
PROCEDURES
..
1-18. Test Connections
..
.
.....
.
1-19.
Meter
Mechanical
Zero
Adjustment.
1-20. Frequency Adjustment
..
.
..
. .
1-21.
Impedance/Load
Configuration
..
.
1-22.
Level
Adjustment
....
. .
..
.
1-23. Distortion
Measurement
.......
..
.
..
.
1-24. Distortion
Measurement
with External
Oscillator
.
1-25.
AC
Signal
Level
Measurement.
1-26.
Level
Ratio
Measurements
-
PRINCIPLES
OF
OPERATION
..
INTRODUCTION
.. ..
....
..
DISTORTION
ANALYZER
.
...
.
2-3. General Description.
2-4. Buffer Amplifier
..
2-5. Overload Detector
..
2-6.
Notch
Fi
1
ter
. . . . . . . ·. . . . .
2-7. Distortion Amplifier
and
Attenuator.
2-8. Amplitude
Null
Control
2-9.
Phase
Null
Control
2-10.
Sum
Point Buffer
..
2-
11
:
Tuning
Indicator
..
2-12.
Filters
.
..
..
. .
2-13.
Fun
ctio
n Switches
..
2-14. Meter
Preamplifier.
2-15.
AC
Meter
.....
.
GENERATOR
...
.
.....
.
2-17. r.eneral Description.
2-18.
Oscillator
Circuit
2-19. Amplitude
Cont
rol
..
2-20. Attenuator
....
.
2-21.
Balanced
Amplifier.
POWEP.
SUPPLIES.
. . . . . . .
2-23. General Description.
2-24. Input
Circuit.
2-25.
+15
Vdc
Supply . . .
2-26 -15
Vdc
Supply
..
.
2-27.
+17
Vdc
Supply
..
.
2-28. -17
Vdc
Supply
...
.
2-29. Floating
Ground
Supply
..........
.
2-30. Electromagnetic Interference Consideratio
ns
.
PAGE
.r-r
.1-1
.1-1
.1-1
.1-1
.1-1
.1-2
.1.2
.1-2
.1-3
.1-3
.1-3
.1-5
.1-5
.1-5
.1-5
.1-6
.1-6
.1-6
.1-7
.1-7
.1-7
.1-7
. .1-8
. ·.1-8
.1-9
.1-10
.
2-1
.2-1
.2-1
.2-1
.2-2
.2-2
.2-2
.2-2
.2-2
.2-3
.2-3
.2-3
.2-4
.2-4
.2-4
.2-4
.2-4
.2-4
.2-4
.2-5
.2-7
.2-8
.2-8
.2-8
.2-8
.2
-8
.2-8
.2-8
.2-9
.2-9
.2-9
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TABLE OF CONTENTS continued
SECTION III
- . MAINTENANC E
3-1.
3-2.
3-3.
3-4.
3-5.
3-6.
3-21.
3
-3 7.
3-
38.
3- 39.
3-40.
3-41.
3-45.
3-46.
SECTIO N IV -
4-1.
4-2.
4-3.
SECTIO NV -
5-1.
5-2.
I:HRODUCTIOfL
PART l - BASIC SYST EM OPERATION.
PERFORMANCE CHECK.
TROUBL E SHOOTING .
SYMPTOM/CAUSE TAB LE
PAR T 2 - CO MPLE TE SYSTEM CHECK
TEST EQ UIPMENT.
INTRODUCTION.
3-7. Circuit Co111110n Isolation Chec k
3-8.
Frequency and Level Check.
3-9. Distortion T est.
3-10. Ba lance Ch eck.
3-11. Vernier
Level Control Range Check.
3- 12. 1 and 0.1 dB-Per-Step Level Co ntrols
3-13. +26 and +20 dBm Level Checks
3-14. 10 dB-P er- Step Level Co ntrol, Ba la nc ed Loads
3-15. 10 dB -Per-Step Level Co ntrol , Unbala nced Loads
3-16. dB Volts Test. - .
3-17. Volts P
ower Test .
3-18.
Filters Test .
3-
19. Re si dual Noise Test.
3-20.
Co111110 n Mode Rejection Test
PA RT 3 - ADJUSTMENT and C ALIBRATI ON PROCEDURE.
INTRODUCTION. . .
3-22 . - 17 Volt Adjustment. . ,
3-23.
+17 Volt Adjustment. .
3-
24. Oscillator Photocell Ad just ment .
3-
25. Oscillator Integrator Vo ltage Chang e Adjustm ent .
3-26. Oscil1a·
tor Integrator Outp ut Adjustment. ,
3-27 . Oscillator xlOO O Frequency Ra n ge Adjustment.
3-
28 . Amplifier Balance.
3-
29 . Ver n ie r Attenuator Range
3-30. +15 Vo lt Adj ustm ent.
3- 31. -15 Volt Adjustment.
3-32.
DC Zero Adjustment.
3-33 . Null Adjustment. •
3-34.
Phas e Null Inte grator Voltage Adjustment
3-35 . Tuning In dic ator .
3-36. Calibration
at 1 kHz .
CO MPONENT REPLACEMENT-CALIBRATION ANO ADJUSTMENT.
PART 4 - REPLACEMENT and REPAIR .
S
PECIAL PRECAUTIONS .
WI RING.
SO L DERING TECHNIQUES.
COMPO NENT REP LACEMENT .
3-42.
Mult i -Lead Devices
3-43. Potentiometers
3-44. Analyzer
Power Supply .
OSCILLATOR ACCESS .
FREQUENCY MODULE REPAIR .
3-47. Repair
and Replac ement
3-48. Re pair Instructio ns .
DIAGRAMS
I NTROOUCT ION.
SCHEMAT IC DIAGRAMS.
CO MP ONEN T LOCATION DIAGRAMS
SPAR E PARTS
INTRODUCTION.
ORDERING INFORMATION.
3-1
3-1
3-1
3- 2
3-3
3-3
3-3
3-3
3-3
3-3
3-8
3-8
3
-9
3-9
3-
10
3- 10
3- 11
3- 11
3- 12
3- 12
3- 13
3- 13
3-14
3-14
3-14
3-14
3- 14
3- 15
3-15
3- 15
3-15
3-16
3-17
3-17
3-17
3-
17
3- 18
3- 18
3-19
3-
19
3- 20
3-2 0
3-
20
3-2 0
3-21
3- 21
3-
21
3- 21
3- 21
3- 22
3- 22
3-23
4-1
4- l
4-1
5- 1
5- 1
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1-1.
SCOPE
OF
SECTION
SECTION
1
OPERATION
This section contains information
and
instructions
necessary for the operation
of
the
Sound
Technology
Model
1710A
Distortion
Measurement
System. Included are
power
requirements,
cabling information
and
operating
instructions.
1-2.
I~TROOUCTION
The
Model
1710A
Distortion
Measurement
System
co111>1nes
a
flexible
ultra-low-distortion
sine-
wave
signal generator, a high-resolution automatic-measuring
total
harmonic
distortion
(THO)
analyzer,
and
an
accurate ac-level meter
in
one instrument. Pushbutton operation
permits the operator
to
quickly measure voltage
or
power
levels,
set
level,
and
then
measure
distortion.
The
generator section provides a pure sine-wave
oscillator
signal
for
testing
from
10
Hz
to
110
kHz.
The
generator output
is
direct
-coupled
(no
transformer)
and
is
balanced
and
floating
with respect
to
ground.
Either
side
can
be
grounded without
any
level change.
The
output
impedance
can
be
set
to
either
150
ohms
or
600
ohms
(except
for
levels
greater
than
+21
dBm),
and
discrete
calibrated
levels in 0.1
dB
steps
can
be
selected
from
+27.0
dBm
to
-90.9 dBm(decibcls
relative
to
1
milliwatt
into
600
ohms)
into
150-ohm
or
60Q-ohm
loads (17.32 V
rms
maximum).
The
level across
any
load used can,
in
addition,
be
directly
measured within the instrument.
An
indicating
off
switch disables the generator for
convenient
signal-to-noise
ratio
(SNR)
measurements.
The
analyzer section contains a tracking notch
filter
which
is
always tuned
to
the
generator's
frequency.
The
analyzer measures
total
harmonic
distortion
with a
sensitivity
ranging
from
100
percent
to
.01 percent
full
scale
, with automatic nulling
on
all
ranges.
Active
filters
may
be
selected
for
hum
and
noise suppression, enhanci ng the
measur
e
ment
resolution. A
differential
front
end
rejects
c011100n
-
mode
noise.
The
ac
signal-level
meter in the analyzer measures
ac
voltage,
or
power
in
dBm.
The
measurement
range
for
ac
voltage
is
0.1
millivolts
to
100
volts
full
scale
(30 microvolts
using the
RATIO
switch described in paragraph 1-25).
and
for
power
i~
-80
dBm
to
+40
dBm
full
scale (-90
dBm
using the
RATIO
switch described
in
paragraph 1-25). Ratio measure-
ments
with
100
dB
or
more
of
dynamic
range
can
also
·
be
made
.
1-3.
INPUT
POWER
REQUIREMENTS
The
Model
1710A
System
may
be
operated
from
nominal
115-volt (90
to
130)
or
230-volt
(180
to
260),
50
or
60
-
Hz
power
sources. A two-position
selector
switch
on
the
rear
panel
selects
the
nominal
voltage; before connecting the instrllllent
to
the
power
outlet,
check
that
the
selector
switch
setting
matches the voltage of the source.
The
Model
1710A
System
is
protected
from
ac
power
overloads
by
a fuse (lA, fast-blow)
located
in
a
cartridge-type
fuse holder
on
the
rear
panel.
1-4.
POWER
CABLE
The
International Electrotechnical
Commission
(IEC)
recommends
that
instrument panels
and
cabinets
be
grounded
to
protect operating
and
servicing personnel.
The
Model
1710A
system
is
equipped with
an
!EC-approved three-conductor
power
cable assembly which,
when
plugged
into
an
appropriate
outlet,
effectively
grounds the
unit.
1-5.
CONTROLS
ANO
INDICATORS
The
data sheet
at
the front
of
this
manual
illustrates
and
describes
briefly
the
Model
1710A
Distortion
Measurement
System's front panel controls
and
indicators.
The
following
provides additional explanatory information.
1-1

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1-6 AC INPUT
a.
1- 7
POWER ON switch -- Connects ac Power to Model 1710A System.
SINE WAVE GENERATOR
a. FAST RESPONSE/LOW DISTORTION switch -- Selects operating mode of oscillator. FAST
RESPONSE causes oscillator amplitude to settle quickly after a frequency change.
This
mode is recorrrnended when ultra - low distortion measurements are not required.
for
example when making frequency response measurements. LOW DISTORTION selects
full ultra-low d is tortion capability of oscillator. The settling time in this mode
is less than 5 seconds. Actuation of the FREQUENCY pushbuttons generally causes the
oscillator to go first to the Fast Response mode and then settle in Low Distortion
mode. This switch controls on ly the oscillator and is not connected to the analyzer.
b.
OSC FAST RESPONSE indicator -- Indicates operating roode of oscillator . When lit.
oscillator is in Fast Response mode and does not have ultra - low distort io n.
c. FREQUENCY pushbuttons -- Simultaneously select generator and total harmonic distortion
analyzer frequency. Four multiplier switches and 30 dig it switches pennit 3-digit
resolution within each range. Frequency range of Model 1710A system is 10 Hz to
109 .9 kHz. On e button on each row roost be pressed at all times .
d. OFF switch -- Disconnects the generator while maintaining the source termination of
the output tenninals
at 150, 600 or zero ohms (+26 dBm position on lOdB switch)
e.
GENERATOR LEVEL switches -- Allow selection of calibrated output levels into 150-ohm
or 600-ohm loads when VERNIER control is at mid-rotation. These levels are from
+ 26.0 dBm to -89.9 dBm ( Note that since the VERNIER controls has a range of
~ 1 dBm from this midpoint setting, the full range is from+ 27.0 dBm to -90.0
dBm.) For other load impedances, output levels are not calibrated but may be
measured directly across the load by placing the ANALYZER SELECT switch in the
OUTPUT position while using the analyzer in the VOLTS/PC1,IER function. Signal
clipping
can occur for loads of less then 150 ohms in the +26 dBm position on the
10 dB switch (the generator source impedance is fixed close to zero ohms).
f. VERNIER control -- Varies the output level linearly i 1 dB from nominal .
g.
OSC 1F control -- Varies the oscillator frequency by t 3/4 of the least sionificant
disit . This setting does not affect the nominal center frequency of the total
harmonic distortion analyzer, nor its ability to null on the generator signal.
h. GENERATOR OUTPUT tenninals -- Provide direct-coupled and balanced generator output
with a mid-point reference
(CT) tenninal . Output floats with high isolation with
respect
to chassis ground. Generator GND tenninal is fused on rear panel (1/32 A,
fast-blow).
i. SOURCE IMPEDANCE switch -- Provides 150 - ohm or 600-ohm source impedance as selected.
except that source impedance is near zero ohms when+ 26 dBm position of most-
significant GENERATOR LEVEL switch is selected.
1-8
TOTAL HARMONIC DISTORTION (THO) ANALYZER
a. INPUT tenninals -- Provide connection for external signal being measured.
b. VOLTS/POWER pushbutton -- Selects ac level measurement function.
c. SET LEVEL pushbutton -- Selects Set Level function whereby meter displa ys reference
signal level for Total
Harmonic Distortion or Ratio measurements.
d. THO pushbu tt on -- Selects Total Harmonic Distortion measurement function.
e.
dB VOLTS pushbutton -- Selects Ratio measurement function.
1- 2
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f. ANALYZER SELECT/GENERATOR OUTPUT switch -- Selects the input to the analyzer circuits
from the · INPUT terminals or the GENERATOR OUTPUT TERMINALS .
g.
INP UT switch -- Selects full-scale meter range for ac level measurement function.
Readings are in volts rms or dBm (600 ohms). Also selects input range for Total
Ha rm onic Di stortion and Ratio measurem ent functions.
h.
RATI O sw itch -- Selects full scale meter range for Distortion and Ratio measurement
functions. Readings are in percent or dB.
i . OVERLOAD indicator -- Lights when INPUT switch setting is too low or when ADJUST
control is set too far clockwise. This warns operator that measurement is no
long er accurate.
j. SET LEVEL ADJUST control -- Adjusts reference signal level for Total Hanoonic
Distort i on or Ratio measurement. When control is set to CAL position (maximum
counterclockwise, before selection of Auto Set Level, if provided) RATIO ranges
extend level
measurement to 30 Microvolts or -90 dBm full scale (refer to paragraph
1-25) .
k. FILTERS -- HUM pushbutton selects a filter which suppresses low-frequency siqnals
THO / VOLTS (s uch as 60-Hz h um) bel ow 40 0 Hz. NO IS E pushbutton selec ts a fi l te r wh ic h
suppresses hiq
h-f requ ency no is e a bove 30 k Hz or 80 kHz, as selected . The NO ISE fi lter
helps re duc e e ff ects of Al •l r ad io s tation pickup. The HUM filter is usable with fun -
da me ntal fr e quen cies dow n to 4 00 Hz when mak i ng distort i on measurements. Both f il ters
affect readi ngs onl y on Di stort i on and Ratio measurement functions. They do not
affect m
ete r readi ngs on VOLTS / POWER, and Set Level measurement functions.
1.
m.
NOTCH frequency indicators -- Facilitate analyzer tuning when using an external
oscillator. When LOW indicator is lit, analyzer frequency is low with respect to
incoming signa. l; when HIGH indicator is lit, analyzer frequency is high with
respect to
incoming . signal. Analyzer is correctly tuned when both indicators are
extinguished.
(It is normal for one of these indicators to glow when there is no
signal input to the Model 1710A.)
METER -- Indicates signal level of measurement selected by ANALYZER function pushbutton.
n. INPUT f,()NITOR BNC connector -- Provides replica of input signal being analyzed.
This signal
is referenc~d to ground and intended to be connected to an oscilloscope.
Outout
is 316 millivolts for full - scale meter deflection in Set Level mode with
INP UT range switch equal to or more than 0.3 V.
o.
OUTPUT MONITOR BNC connector -- Provides replica of distortion products of signal
being analyzed
(suitable for viewing on oscilloscope) on VOLTS/POWER, SET LEVEL
and DISTORTION measurement functions. On Ratio measurement function, this output
provides a scaled version
of input signal. Output is 31 .6 mi ll ivolts for full-
scale meter deflection, and is referenced to ground.
· 1-9. A
UTO S ET LE VE L
Re f er to Ap pend ix A for a desc ription of th is cont ro l.
1-10. INTERl,ODULATION DISTORTION (IMO) ANALYZER
1- 11.
Re fer to App end ix B for a des cr io ti on of the IM O Anal y zer controls .
TEST SETUP
In order to take full advantage of the ultra-low distortion measuring capabilities
of the Model 1710A system, it is extremely important that the cabling between
the Model 1710A, the device under test, and other test equipment be connected in
compliance with the arrangement shown in Figure 1-1 and described in the following
paragraphs.
The connections and controls numbered in Figure 1-1 are similarily
identified in the text. These connections have been found to provide the optimum
test setup in most cases.
1- 3

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......
I
.s:,,.
OSC
ILLOSCOPE
CHANHCL
•
~
•
----
0
c::r:::J
CJ
CJ
CJ
D
CJ
•
1 .....
14
@
(Q)
INP\J
-------J
Figure 1-1. Model 1710A T
•
o e
DEVICE
UNDER
TEST
• •
D
CJ
est
Setup
•

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1-12.
POWER
CONNECTIONS
a.
b.
Check
that
the
power
slide
swit
ch
on
the
rear
panel
of
the
Model
1710A
is
set
to
the
correct
position for the available ac
power
(see paragraph 1-3 for
details)
.
Do
not
float
the earth
ground
of
the
power
cord
of
the
ft>del
1710A.
(The
analyzer's
differential
input
makes
this
steµ unnecessary
for
breaking ground loops.)
c. Plug the
Model
1710A,
the device under
test,
and
the oscilloscope
(if
used)
into
the
ac
power
bus
as closely together as possible.
1-13.
GROUND
CONNECTIONS
a. Connect the
Model
1710A
GND
tenninal
at
the analyzer input (1)
to
the
ground
terminal,
or
chassis ground,
of
the
device under
test
using as
short
a lead as
possible
of
at
least
No.
18
AWG
stranded
wire.
This reduces
conmon-mode
potential
between
these
two
devices.
In
a strong
hum
or
RF
field,
this
connection
is
essential.
~.
Connect the oscilloscope
(if
used)
to
the
INPUT
l()NITOR
BNC
connector (2)
on
the
Model
1710A
via cable (3) .
NOTE
(1) This cutput
is
from
the
differential
to
single-ended converter
in
the
Hodel
1710A
which
provides a
replica
of
the input signal . This signal
is
referenced to
ground.
(2)
If
a
BNC
cable
is
not used for
this
connection, the oscilloscope
conmon
(low)
terminal
must
be
retumed
to
the
Model
1710A
GND
terminal (1) via a
direct
connection
(4).
-
1-14.
SIGNAL
CONNECTIONS
Connect the oscilloscope
(if
used)
to
the
OUTPUT
P()NITOR
(5)
via cable (6) .
This permits monitoring the
distortion
products
of
the signal being analyze~.
1- 15.
GENERATOR
a.
Set the
OUTPUT
IMPEDANCE
selector
switch (13) to
150
ohms
or
600
ohms
as desiTed
for the device under
test.
b.
Set the
10
dB
level switch (7)
of
the
GENERATOR
LEVEL
controls
to
-80
dBm
or
to
a
known
safe
operating input level
for
the device under
test.
The
other
level switches,
as well as the
VERNIER
control
and
the
OFF
switch,
can
be
at
any
setting
at
this
time.
c.
Connect
the shielded twisted-pair cable (8)
between
the
GENERATOR
OUTPUT
terminals
(9)
and
the input tenninals
of
the device under
test.
The
shield (10)
of
this
cable
should
be
connected to the
GENERATOR
OUTPUT
GND
terminal (11) only,
and
not
to
the
chassis
of
the device under
test
(12).
NOTE
(1)
In
environments with high
electrical
or
radio-frequency noise,
it
may
be
necessary to use a shielded dual bananna-plug connector
such
as the
Pomona
Type
1921
at
the
GENERATOR
OUTPUT
terminals, as well as
an
appropriate shielded connector
at
the input
to
the device under
test.
(2)
If
the input
to
the device under
test
is
single-ended,convert the balanced
output to unbalanced
by
connecting a short wire (about 1 inch)
between
the generator
GND
terminal
and
the adjacent output terminal.
Once
this
ground
connection
is
(
3)
made,
a
single
conductor shielded·cable can
be
used
to
feed signal
into
the device
under
test
.
ie
certain
that
no
significant
voltages will
be
presented
to
the
GENERATOR
OUTPUT
terminals
from
the device under
test.
Voltages
greater
than 7 volts
rms
across the balanced output,
greater
than 5
volts
rms
from
either
balanced output
terminal to the
CT
terminal,
or
greater
than
200
volts
rms
between
any
of
the output
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terminals and chassis ground may lead to permanent attenuator resistor and / or
semiconductor damage . No fusing of these signal lines is provided so that si£~al
distortion can be kept to a minimum.
1- 16. ANALYZER
a. Set the INPUT switch to 100 V or expected range and select the VOLTS/P O WER function.
b. Set the ~ALYZER SELECT switch to INPUT (out position).
c. Connect the output of the device under test to an appropriate load resistor, if
required.
NOTE
This load resistor and the output connections should be made in a location fre e
from any ac magnetic fields, such as caused by power transformers, to avoid hum
pickup. ·
d. Connect the output of the device under test to the analyzer INPUT terminals (14)
with the shielded twisted-pair cable (15). Connect the
shield (16) of this cable
to the
INPUT GND terminal ( l); do not connect the shield (17) at the de vice under
test .
NOTE
(1) In environments w ith high electrical or radio-frequency noise it may be
(2)
necessary to use a shielded dual bananna-plug connector such as the Pomona Type
1921 at the analyzer INPUT terminals, as well as an appropriate shielded connector
at the output of the device test.
Each INPUT terminal has its own input attenuator and buffer amp'ifi er.
Input impedance is 100 Kilohms from each terminal to the Model 171UA Sys te mgrounc.
The true differential input circuits of the Model 1710A System help break the
ground loop
that causes 60-Hz pickup on the input leads of most measur~ng equipment.
(3)
Do not connect one channel of the oscilloscope directly to the output of the device
under
test as this can reduce the noise rejection capability of the Model 1710A
System differential input circuitry. If it is absolutely essential to monitor this
signal, leave the ground lead of the scope channel disconnected from the device
under
test.
1-17. OPERATING PROCEDURES
tAUTION\
DO NOT EXCEED THE FOLLOWING ANALYZER INPUT VOLTAGES, TO PREVENT RLOWING F USES
Fl and F2, located inside the 1710A. With INPUT range switch set to 3V or lower:
(1)
300 V below 60 Hz
(2) 50 V above 1 kHz
1-18. TEST CONNECTIONS
Before making measurements with the Model 1710A System, ensure that the
equipment
has been connected as shown in figure f-1 and following the instructions
given in paragraphs
1-13 through 1-16 .
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1-19. METER MECHANICAL ZERO ADJUSTMENT
1- 20.
a.
The meter is correctly set when the pointer rests over the zero calibration
marks on the scale when the Model 1710A INPUT switch is set to 100 V, the SET LEVEL
pushbutton is pressed, and there is no input signal (in put leads disconnected).
To adjust the zero set: Rotate the zero adjustment screw (located on the front
panel
below the meter) until the pointer is left of zero. (This may require either
CW or CCW rotation.) Reverse rotation until the pointer is exactly at zero.
FREQUENCY ADJUSTMENT
Four Multiplier pushbuttons (Xl , XlO, XlOO XlOOO) and 30 Digit pushbuttons permit
3-digit resolution of frequency selection. For example, 453 Hz is selected by
pressing the fo 11 owing pushbuttons:
Multiplier
1st Digit
2nd. Digit
XlO
40
5
3rd. Digit
.3
Frequen cy
40Xl0=400
5XlQ: 50
. 3Xl0= 3
453 Hz
The "100" Digit pushbutton provides a 10 percent overlap in range. For Example,
101 0 Hz can be selected in two ways:
Multiplier
1st. Digit
2nd. Digit
XlO
100
1
XlOO
10
0
3rd. Digit
0
.1
Frequen cy
lOOX 10= 1000
lXlO= 10
OXlQ: 0
1010 Hz
10Xl00= 1000
OXlOO= 0
.
lXl OO= 10
1010 Hz
b. In the Xl range, operation of the frequency pushbuttons may not always cause the
oscillator to go through its automatic stabilization cycle. If the osc illator
amplitude appears to be unstable, momentarily set the FAST RESPONSE/LOW DISTORTION
switch to the FAST RESPONSE position and then return it inmediately to the LOW
DISTORTION setting.
c. The OSC ~F control can be used to provide frequency resolution between digitally -
selected values.
1-
21. IMPEDANCE/LOAD CONFIGURATION
With the SOURCE IMPEDANCE select switch set to 150 ohms or 600 ohms, the
generator
is matched to either of these load imped ances except when the most
significant GENERATOR LEVEL control is set to +26 dBm. The matched condition wil l
exist for balanced or unbalanced loads, as long as the signal connections of
paragraph 1-13 through 1-16 are used. For load impedances other than l~O ohm~ or
600 ohms. source matching can no longer be achieved and the output conf1gurat1on
must be considered as a voltage divider with a source impedance as selected; the
degree
of b~lance will not be affected by other load impedances.
1-
22. LEVEL ADJUSTMENT
a. For 150 or 600 ohms
(1) Center the GENEqATOR LEVEL VERNIER control.
(2) Set the
GENERATOR OFF switch to the on (out) oosition.
(3) Adjust the
GENERATOR LEVEL switches for the desired level.
1-7

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NO TE
The 1 dB / step and 0.1 dB / step sw itch es al wa ys su btract nu m er ic a lly fr om
the level indicated in the most-signi ficant level swit ch ; i.e.:
+20
-50
-3
-4
-.7
-.2
= +16.3 dB m
= -54 .2 dBm
b.
To confirm the actual signal level presented to the load, set the AN AL YZ ER SEL ECT
switch to GENERATOR OUTPUT , and using the VOLTS / PO WER function, dir ectl y me a su re
the output level in
volts or dBm (600 ohms ).
1-23. D ISTORTION ME ASU REMEN T
To measure the total hannonic distort ion ( THO) of a device under t est, pr oc eed
as
foll o ws :
a. Set the
FAST RESPONSE/LOW DISTORTION switch to LOW DISTORTION and select t he
fundamental test frequency in Hz by depressing the appropriate FRE Q UENCY pushbutton s.
b. Press V OLTS / POWER pushbutton and set the ADJUST co ntrol fu lly C CW to C AL po si tion.
c. Set the
INPUT switch to the expected range.
d. Set the ANALYZER SELECT switch to INPUT (out position).
e. Adjust the GENERATOR LEVEL controls for the des ired input level to the device und er
test.or for the desired output level as indicated on the Model 1710A me te r. Up
range the
INPUT switch when the meter pointer passes full scale and down range
when the meter pointer goes below 1/3 of full scale . An input level of at lea st
0.1 Vis needed for THO measurements.
f.
For percentage THO measurements, press the SET LEVEL pushbutton and rotate the
ADJUST control until the meter pointer rests on the full-scale mark. ( If au to
set level is to be used, replace this step with rotation of the ADJUST co ntrol
fully CCW past the click to AUTO.)
NOTE
If distortion is to be measured in dB, the AD JU ST control should be r ot at ed
until the meter pointer rests on the OdB mark; this will require upranging of
the
INPUT switch one step if the initial level reading is above this scale poin t.
(Auto Set level always adjusts for full-scale reference, and requires t he addit i on of
2dB to dB THO readings made using this feature.)
g. Press the DISTORTION pushbutton and r otate the RATIO switch until the meter p ointer
reaches the upper 2/3's of scale. If desired, press the HUM or NOISE (3 0 Hz or 80
KHz FILTER pushbuttons to filter noise from the input signal.
h. Observe the distortion either in percentage or dB, as indicated by the m eter
deflection and the RATIO switch setting.
1-24. DISTORTION MEASUREMENT WITH EXTERNAL OSCILLATOR
a. Connect the equipment as shown in Figure 1-1, with the foll owing exception s:
( 1) If possible, connect the power cord of the external osc illator to a main po wer
source close to the source used by the Model 1710 A, the device under t est , a nd
the oscilloscope.
(?.) Connect the output of the oscillator to the input of the device under te s t. The
oscillator output may be floated if this gi ve s better t est results .
( J)
If possibl e, connect the c hassis of the osc illator to the ana lyzer GNO terminal
. of the Model 1710A.
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b.
c.
d.
e.
f.
g.
h.
i .
j.
K.
1-25.
a.
b.
c.
d.
Set the external oscillator to the desired frequency. 5et its output level to
minimum.
Preset the Model 1710A FREQUENCY pushbuttons to the approximate frequency of the
external
oscillator. ·
Set the
ADJUST control fully counterclockwise (CCW) to the CAL position and press
the
VOLTS/POWER pushbutton.
Set the
INPUT switch to the desired input level.
Set the ANALYZER SELECT switch to INPUT .
Adjust the external
oscillator amplitude control for the desired input level to
the device under
test or for the desired output level from it, as indicated on the
Model 1710A meter. Input level must be in the upper 2/3 of meter scale and at
least O. lV.
Press the SET LEVEL pushbutton. Rotate the ADJUST control until the meter pointer
rests at full scale. (If auto set level is to be used, replace this step with
rotation of the ADJ UST control fully CCW past the click to AUTO position .)
Set the Model 1710A frequency or the external oscillator frequency so both NOTCH
FREQ U ENCY indicators are off and the tuning is approximately centered.
Press
the DISTORTION pushbutton and set the RATIO switch for an on-scale meter
reading as high as possible.
If desired, press the HUM or NOISE (30 or 80 kHz)
FILTER .
Observe the
distortion in either percentage or dB, as indicated by the meter
deflection
and the RATIO switch range setting.
AC SIGNAL LEVEL MEASUREMENT
The Model 1710A is an accurate ac level meter over its entire frequency range.
The power scale is calibrated in dBm across a 600 - ohm load. Voltage may be
measured directly from 0.1 millivolt to 100 volts full scale and power from - ao
dBm to +40 dBm full scale. To measure ac voltage or power, proceed as follows:
Ensure
that the power and ground connections are as described in paragraphs 1 -1 2
and 1-13 respectively.
Connect the signal to be measured as described in paragraph 1-16.
Set the
ADJUST control to CAL position and press the VOLTS/POWER pushbutton.
Rotate the
INPUT switch for an on - scale reading with the pointer in the upper 2/3's
of the meter scale.
NOTE
The HUM and NOISE FILTERS do not affect readings in the VOLTS / POWER measurement
mode.
e. The sensitivity of the ac voltmeter can be extended to 30 microvolts full scale
through the use of the RATIO switch. To obtain this increased sensitivity, carry
out the following
steps:
(1) Set the Model 1710A controls as follows:
dB VOLTS switch -- ------------- - ------- in
INPUT switch-- -- --------------- - ------- .3 V
ADJUST control -- - -- - -- -- --------------- CAL
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(2) Meter full scale sensitivity is now controlled by the
RATIO switch as follows:
RATIO switch
-80 dB
-70 dB
-60 dB
-50 dB
NOTE
Full Scale Sensitivity
30 u V
100 u V
300 u V
1 mV
The HUM and NOISE FILTERS will affect meter readings in this mode of
operation.
1-26.
LEVEL RATIO MEASUREMENTS
The dB Volts function facilitates the measurement of voltage ratio, signal-
to-noise
ratio, and frequency response, in dB or percent. The signal-to-noise
ratio measurement using the internal sine-wave generator of the Model 1710A as
described
below provides an example of the use of this function.
a. Ensure that connections are as described in paragraphs 1-13 through 1-16, and
Figure 1-1.
b. Set the ADJUST control to the CAL position and press the VOLTS/POWER pushbutton.
c. Set the
INPUT switch to the expected signal range and adjust the appropriate signal-
level controls for the desired output
signal, as indicated on the meter.
d. Press th~
SET LEVEL pushbutton and rotate the ADJUST control until the meter
pointer
rests on the O dB mark for dB ratio measurements or on full scale mark
for percentage ratio measurements.
NOTE
For proper O dB or 100 percent set level, the reference signal must be at
least 0.1 V and not exceed 100 V.
This step must be carried out manually; Automatic Set Level cannot be used
for this measurement.
e.
Remove input signal to the device under test by pressing the OFF pushbutton.
f. Press the dB VOLTS pushbutton. Select the RATIO switch range which places the
meter pointer in the upper
2/3's of scale if possible. Read signal-to -noise
ratio (SNR) as indicated by the meter deflection and the RATIO switch range
setting.
1-10
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SECTION II
•
PRINCIPLES OF OPERATION
•
•
2-1. INTRODUCTION
The Model 1710A nistortion Measurement System consists of a flexible ult ra-low-
distortion sine-wave signal generator, a high-resolution automatic-measurin9 total harmonic
distortion (THO} analyzer, an accurate ac-level meter, and de power supplies. Pushbutt on
operation permits the operator to quickly measure voltage or power levels, set level, and
measure distortion.
The system makes total harmonic distortion measurements by applyil'g a sine -w ave of
ultra-low distortion from the generator to the input of the device under test while the
distortion analyzer measures the output from the device under test. A tuneable notch
filter in the analyzer, mechanically ganged to the generator by the front panel frequency-
select switches, suppresses the fundamental signal. Automatic nulling circuitr_y fine
tunes the notch
filter and ensures that the null is retained. The signal remaining at the
output
of the notch filter consists of the distortion products and noise. This is displ3yed
by the average-reading volt -meter in the analyzer. The ratio of the measured distortion
components to a previously set fundamental signal reference level is defined as the totJ l
harmonic
distortion and can be read out directly on the meter in percent or dB. Switchable
hum and noise filters are porvided to enhance the readout of the hannonic products.
2-2.
DISTORTION ANALYZER
2- 3. GENE~L DESCRIPTION
Refer to Section IV for a schematic diagram of the distortion analyzer assem t,ly. l\ote
that the circuit is divided into the following circuit blocks: Buffer amplifier, overload
detector, notch filte r, distortion amplifier and attenuator, amplitude null filters, f ur.~ tio r.
switches, and ac meter. The operation of the assembly is discussed first at a circuit t,l oc~
level and is then followed by details of each block.
In operation, the signal to measured from the ANALYZER SELECT switch is conn ected to
the input
of the buffer amplifier. The buffer amplifier has two inputs, a fixed output
which may be connected to the ac voltmeter, and a variable output (controlled by the ADJ U ST
control) which is connected to the notch filter. The voltmeter is an average reading type
which measures the signal level selected by the appropriate function switch.
The overload detector monitors the variable output of the buffer amplifier. If an
excessively high output voltage is detected, the detector turns on the front panel OVERLOAD
indicator.
The notch filter is mechanically ganged to the oscillator frequency select switches
and suppresses the fundamental from the output of the buffer amplifier. The output of
the notch filter is connected to the input of the distortion amplifier through a step
attenuator controlled by the front panel RATIO switch. The attenuator adjusts a signal
level
for the distortion amplifier for various percentages of distortion or ratio readings.
The amplitude null control and phase null control circuits supply the notch filter
with its automatic nulling feature. Both circuits monitor the output of the distortion
amplifier and feed control signals back to the notch filter.
The sum-point buffer supplies reference signals to the tuning indicator and to the
amplitude null control
circuit.
Th e tuning indicator circ v it, using frequency information from the notch filter,
provides the operator with a visual indication of the frequency being analyzed versus the
input frequency. This
circuit operates the NOTCH filter HI and LO indicators.
The switchable HUM and NOISE filters are connected to the output of the distortion
amplifier. These filters are effective on DISTORTION and dB VOLTS measurements.
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The function switches select the circuit to be measured by the ac voltmeter.
when the VOLTS POWER switch is depressed, the meter monitors the fixed output from
the buffer amplifier via a stepped attenuator and preamplifier. When the SET LEVEL •
switch
is depressed, the meter rronitors the va r iable output fro~ the buffer amplifier.
Operation
of the TH Oswitch routes the signal from the distortion amplifier via the
HUM and NOISE filters (if selected) to the meter. When the dB VOLTS switch is depressed,
it connects the variable output from the buffer amplifier directly to the attenuator at
the input of the distortion amplifier and hence to the met er.
2-4. BUFFER AMPLIFIER
The input of the buffer amplifier contains a pair of step attenuators, one for
each
INPUT connector. The attenuators are controlled by Sections SlA, B, C, D of the INPUT
switch. The attenuator outputs are connected to input signal preamplifiers UlOl and Ul02 .
The gain of these units is controlled by section SlE of the INPUT switch. Gain is unity
on the 3 V range and above, 3.16 on the l V range, and 10 on the .3 V range and below.
The preamplifier outputs are coupled to Ul03, a bridge amplifier circuit which effectively
acts as a differential to single -ended converter with high co111110n-mode noise rejection.
The gain of the bridge amplifier is controlled by ADJUST potentiometer R125 and provides
the variable signal supplied by the buffer. The range of gain is 10 dB and full scale
voltage is 3. 16 volts. The fixed output from the buffer is obtained between the wiper
of R125 and ground. This signal remains fixed regardless of the setting of Rl25, except
when the buffer overloads.
2-5.
OVERLOAD DETECTOR
The overload detector signals an overload condition when the variable output of the
buffer amplifier exceeds approximately
6.5 volts rms sine wave or 9 vo l ts peak. The
ci rcuit consists of comparator Ul07, a half-wave rectifier and filter, a light-emitting
diode driver, and OVERLOAD indicator CR120.
2-6. NOTCH FILTER
The notch filter consists of two 90-degree phase shifters connected in series, making
the output 180 degrees out of phase with the input. By sunming the input and output at
su rrming ampl ifier U203, the fundamental of the input signal is cancelled out. Feedback
from the output of the surrmi ng amp 1i fi er to the input of the filter increases the Q of
the circuit and narrows the rejection band of the filter.
Tuning is controlled by changing a set of RC elements for each phase shifter through
operation
of the front panel Multiplier and Digit pushbutton switches. When the reactance
of the capacitance equals the resistance at the incoming frequency, the phase shift is
90 degrees. The RC components are contained in the frequency module (See section
IV for schematic diagram).
2-7.
DISTORTION At-f>LIFIER ANO ATTENUATOR
The output of the notch filter is coup led through a 7-step attenuator to the input
of distortion amplifier U204 . The attenuator is controlled by section S20 of the front
pan el RATIO switch and reduces the distortion product of the notch filter such that the
fu
ll scale voltage input to the amplifier is 1 mV on ranges .03% through 100 % and .316 mV
on the .01 %range.
Amplifier
U204 is a wide-band high-gain unit with gain co ntr olled by sectio n S2E
of the RATIO switch. The gain is 31.6 for ranges .03%through 100 % and 100 for the .01 %
range. This gives a
full scale output voltage of 31.6 mV on all ranges.
2-8.
AMPLITUDE NULL CONTROL
•
The amplitude null control circuit controls the amplitude of the signal from the
cascaded phase
shifter so that exact balance occurs when it is summed with the input to
the phase
shifters. This ensures the total cancellation of the fundame ntal signal. The
componen ts which perform this function include phase detector U310 , floating integrator •
and voltage follower U312, integrating amplifier U311, integrating c apacitors, and a
photocoupler
controlling a variable resistor element in the summing network.
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The
reference input
to
phase
detector
U310
is
a signal
which
is
in
phase with the fun-
damental,
and
the signal input
to
U310
is
the
distortion
product output
of
the
distortion
amplifier.
With
these inputs, the phase
detector
monitors the notch
filter
output
for
an
in-phase
signal.
When
this
occurs.the output
of
the phase
detector
supplies drive to the
integ
rat
or
causing the charge
on
the
integrating
capacitors
to
change. This in turn causes
the
photocoupler to change the value
of
the variable
resistor
which
in
effect
adjusts the
summing
current
until
the in-phase
component
is
no
longer
there.
The
integrating
capacitors
are
changed
by
the
RATIO
attenuator
switch. This in
effect
maintains the automatic null control loop gain
at
a
relatively
constant
level,
resulting
in
high-speed nulling
on
all
ranges.
The
ca
pacitors
are
precharged to the
integrator
output
voltage level through
resistor
R360.
This avoids switching
transjents
and
improves
the
speed
of
the
circuit.
2-9.
PHASE
NULL
CONTROL
The
phase null control
ci
r
cuit
fine tunes the phase
of
the second phase
shifter
in the
notch
filter
so
that
the overall phase
shift
is
exactly
180
degrees. This ensures
total
cancellation
of
the fundamental
signal.
The
compone
nts
which
perform
this
function include
phase
detector
U307,
floating
integrator
and
voltage follower
U309
,
integrating
capacitors,
and
a photocoupler cont
rollin
g a variable
resistor
in the
resistive
branch
of
the second
phase
shifter.
The
reference input to phase
detector
U307
is
a signal
which
is
out
of
phase with the
fundamental,
and
the signal input
to
U307
is
the
distortion
product output
of
the
distortion
amplifier.
With
these inputs the phase
detector
monitors the notch
filter
output
for
an
out-of
-phase
signal.
When
this
occurs, the phase
detector
output supplies
drive to the
integrator
causing the charge
on
the
integrating
capacitors
to
change.
The
integrator
output drives the v
ariab
le
gain
amplifier,
U313,
and
the voltage
to
current con-
verter,
U314,
which
in turn causes the photocoupler
to
change
the value
of
the variable
resistor
which
in
effect
adjusts
the phase angle
until
the out-of-phase
component
is
no
longer there.
The
integ
rating
capacitors are
changed
by
the
RATIO
attenuator
switch. This in
effect
maintains the automatic null control loop gain
at
a
relatively
constant
level,
resulting
in high-speed
nulling
on
all
ranges.
The
capacitors
are
precharged
to
the
integrator
output voltage level through
resistor
R344.
This avoids switching
transients
and
improves
the speed
of
the
circuit.
A
set
of
resistors
that
feed signal
from
integrator
U308
to
U313
,
whi
ch
acts
as a gain
control,
is
switched
by
the front panel
FREQUENCY
switches. This maintains a
relatively
constant integ
rat
or
voltage
when
frequency
is
changed
and
helps
to
achieve
perfect
nulling
in
less
than 5 seconds.
2-10.
SUM-POINT
BUFFER
.
T~e
~um-point buffer suoplies a sig~al
from
the notch
filter
sunming
point
to
the
tuning
1nd~c
ator
and
the amplitude null
control,
each
of
which
uses the signal as the
refer~nce i~put _
of
a phase
detector.
The
buffer
consists
of
unity-gain ampljfier
U301
and
~1gh-g~1n
~igh-speed amplifier
U302.
These
components
convert the
sine
wave
at
the
surmnng
point 1nto a square
wave
signal.
2-11.
TUNINr.
INDICATOR
T~e
tu~ing_indicator mo~itors the phase
relationship
between
the signal input
to
the
notch
f1lter
_s
first
phase
shifter
and
its
output.
The
relationship
is
frequency de-
pendent
and
is
90
degrees
when
the
incoming
frequency
is
exactly the
same
as the tuned
fre-
quency
of
the notch
filter.
The
components
performing
this
function include phase detector
U303,
high-speed
amplifier/drivers
U304,
U305
and
HIGH
and
LOW
indicators
CR301,
CR302.
.
The
reference
~nput
to phase
detector
U303
is
the
signal
at
the input
to
the phase
shifter
(connec~ed via the sum-p?int buffer)
and
the signal input
to
U303
is
the output
of
the phase
shifter.
When
the
incoming
frequen
cy
is
exactly
the
same
as the tuned
fre-
quency
of
the notch
filter
(90-degree phase
relat
ionship
),
there
is
no
output
from
the
phase
detector:
Und~r
t~ese conditions both indicators
are
off.
However,
if
the frequency
of_the notch
filter
is
high
compared
with the input frequency,
U303
produces a
de
output
which
turns on.the
HIGH
indicator.
Conversely,
if
the frequency
of
the notch
filter
is
low
compared
with the output frequency, a
de
output
of
the opposite
polarity
from
U303
turns
on
the
LOW
indicator.
2-3