Tektronix AA 501 Instruction Manual
COMMITTED
TO
EXCELLENCE
Tektronix, Inc.
P.O. Box
Beaverton, Oregon
070-2958-00
Product Group 75
500
97077
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF
INSTRUCTICIN
THIS MANUAL.
MANUAL
Serial
Number
First Printing AUG 1980
Revised
NOV
1981
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Copyright @ 1980
Contents of this publication may not be reproduced in any
form without the written permission of Tektronix, Inc.
Products of Tektronix. Inc. and
by U.S. and foreign patents and/or pending patents.
TEKTRONIX. TEK. SCOPE-MOBILE, and
istered trademarks of Tektronix. Inc.
Printed in U.S.A. Specification and price change privileges
are reserved.
Tektronix. Inc. All rights reserved.
itssubsidiariesarecovered
@
are reg-
O
1980
Copyright
halten. Der lnnalt dieser Publikation darf ohne Genehmlgung
von Tektronix, Inc. nicht weitergegeben werden.
Produkte von Tektronix, Inc. und seinen Tochtergesellschaften
sind durch US- und Auslandspatente
Patente abgedeckt.
TEKTRONIX, TEK. SCOPE-MOBILE und
Warenzeichen von Tektronix, Inc.
Gedruckt in U.S.A. Spezifikations- und
bleiben vorbehalten.
durch Tektronix, Inc. Alle Rechte vorbe-
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@
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Copyright
Le contenu de ce manuel ne peut etre reproduit sous quelque tor-
me
Tous les produits TEKTRONlX sont brevetes
les logotypes TEKTRONI X, TEK SCOPE MOBILE.
dews&.
lmprimb aux USA. TEKTRONIX se reserve le droit de modif~er
caracteristiques et prlx dans le cadre de developpements technologiques.
O
1980
TEKTRONIX INC. Tous droits reserves.
que ce soit sans I'accord de Tektron~x Inc.
US
et Etranger et
'@
01980
R12-79
:
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ARTEK
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TABLE OF CONTENTS
Page
LlST OF ILLUSTRATIONS
LIST OF TABLES v
OPERATOR'S SAFETY SUMMARY vi
SERVICE SAFETY SUMMARY vii
Section
Section
I
SPECIFICATION
Instrument Description
Performance Conditions 1-1
Electrical Characteristics
Environmental Characteristics 1-7
Physical Characteristics 1-8
English Version
2
OPERATING INSTRUCTIONS
Preparation for Use 2-1
Repackaging Information 2-1
Controls. Connectors. and Indicators 2-2
Instrument Connections
Level Measurements
Distortion Measurements
Distortion Measurement Procedure
IM Distortion Measurements
(Option 01)
IM Distortion Measurement Procedure
(Option 01) 2-1 1
Filters
Displays
Monitoring
..................
..................
......................
....................
...................
..........
.........
.........
..........
..............
............
........
.........
............
........
.
1-1
1-2
2-4
2-5
2-6
2-7
2-9
2-11
2-12
2-13
Page
i
v
CHAPITRE 2 INSTRUCTIONS D'UTILISATION
Kapitel2 BEDIENUNGSANLEITUNG 2.1
French Version
Instructions de reemballage pour
expedition
Cornmandes. connecteurs
lumineux
Connexions de I'appareil
Mesures de distorsion
MBthode de rnesure de distorsion
Mesures de distorsion d'intermodula-
tion (option
MBthode de rnesure de la distorsion
par interrnodulation (option
Filtres
Affichages
ContrBle
German Version
................
et
temoins
................
........
..........
01)
............
01)
....................
..................
..................
2-1
2-2
2-4
2-6
.
.
2-8
2-9
.
.
2-1
2-11
2-13
2-13
...........
lnbetriebnahme 2-1
Verpackung des Gerates
Bedienungselernente. Anschliisse
und Anzeigen
Anschlusse an das Instrument
Pegelmessungen
Verzerrungsmessungen
Durchfuhrung der
Verzerrungsmessung 2-7
......................
.............
........................
.......
.....................
..............
................
2-1
2-2
2-4
2-5
2-6
1
lnterrnodulationsverzerrungs-
Messung (Option 01) 2-9
Messung von Interrnodulations-
verzerrungen (Durchfijhrung) 2-11
.................................
Filter 2-11
Darstellungen 2-12
~berwachung 2-13
........................
........................
................
........
REV
NOV
1981
Scans
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ARTEK
MEDLQ
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TABLE
Japanese Version Page
OF
CONTENTS
Section
4
CALIBRATION
(cont)
Page
THE FOLLOWING SERVICING INSTRUCTIONS ARE
.
FOR USE BY QUALIFIED PERSONNEL ONLY
PERSONAL INJURY.
VICING OTHER THAN THAT CONTAINED IN
OPERATING INSTRUCTIONS UNLESS YOU ARE
QUALIFIED TO DO SO
Section 3 THEORY OF OPERATION
Introduction
Input Amplifier
Automatic Gain Control
Notch Filter
Frequency Band Discriminator
Notch Filter Control
Distortion Amplifier
Filters and AC-DC Converters
dB
Converter
dB Offset Generator
dB Ratio Circuitry
6
V
Reference
Dvm
Display Board
Logic Circuitry
Power Supplies
..
15 V Supply
IM
option
@
DO
NOT PERFORM ANY SER-
.
..................
0
a
.............
v
$$
6
@
@
...........
...
@
............
.........
...............
.............
TOAVOID
......
....
:
:
:
...
@
........
......
........
:
3-1
3-1
3-2
3-2
Performance Check Procedure
Introduction
Test Equipment Required
List of Check and Adjustment Steps
Performance Check Summary
Sheet 4-4
Internal Adjustment Procedure
Introduction
Services Available
Test Equipment Required
Adjustment Access
Section 5 MAINTENANCE
General Maintenance Information
Static-Sensitive Components
Cleaning
Obtaining Replacement Parts
Soldering Techniques
Semiconductors
Interconnecting Pins
Coaxial Cables
Square Pin Assemblies
Multipin Connectors
Circuit Board Removal
Front Panel Latch Removal
Magnetic Shield
Jumper Selection for CCIF. AUTO.
or
30 kHz Filter Modification
Rear Interface Information
Functions Available at Rear
Connector
Section 6 OPTIONS
7
Section
REPLACEABLE ELECTRICAL PARTS
....................
..................
SMPTWDIN Measurements
....
................
......
....
................
...........
......
...........
. .
....
...
.........
.............
..........
..............
........
..........
........
.....
.............
...
......
.......
.................
4-1
4-1
4-1
4-3
4-18
4-18
4-18
4-18
4-18
Scam
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ARTEK
MEm
+
REV
JUL
1981
TABLE
OF CONTENTS
(cont)
Section 8 DIAGRAMS AND CIRCUIT BOARD
ILLUSTRATIONS
Adjustment Locations
Component Reference Charts
Schematic Diagrams
Section 9 REPLACEABLE MECHANICAL
PARTS
Fig. 1 Exploded View
Accessories
CHANGE INFORMATION
iii
LIST
OF
ILLUSTRATIONS
Fig.
No.
AA
501 Distortion Analyzer
2-1 Installation and removal
2-2
Front panel controls and connectors
2-3 Typical connections for distortion
measurements. See text
2-4 Block diagram of a basic harmonicdistortion
analyzer
2-5 Transfer characteristics of an audio device
THD test of transfer characteristics
2-6
2-7 Block diagram of a basic IM analyzer
IM test of transfer characteristics in time and
2-8
frequency domain.
Response curves for AA 501 filters
2-9
2- 10 Oscilloscope display of deviation from
linearity
Simplified notch filter and control loop
3-1
3-2 Typical frequency discriminator waveforms
at about 800 Hz
3-3 lntermodulation distortion option block
diagram
4-1 Check step 1. Input impedance
4-2 Check step
4-3 Check step
4-4 Check step 4. Bandwidth
4-5 Check step
4-6 Check steps 6,9,10,11 and adjustment steps
9,
CClF distortion and CClF residual
distortion
Check step
4-7
.........................
.................
......................
...................
.........................
2.
Common mode rejection
3.
Level function accuracy
5.
Residual noise
10, and 11. Total harmonic, SMPTE and
........................
7.
Residual THD
...........
.............
....
.............
.....
....
......
.
........
. .
...
.............
..........
IM
tN
........
Page Fig.
N
0.
i
x
2- 1 residual intermodulation distortion
2-3 4-9 Check step
2-5
2-7 4-12 Check step 14. Function output
2- 7 4-13 Check step 15. Auxiliary input
2-8 4-14 Adjustment test setup for steps 1 and 2
2-9 4-15 Adjustment test setup for steps 3, 4.5,6. and
2-10 5-1 Typical square pin assembly
Check step
4-8
Alternate CClF IM distortion accuracy
4-10 Check step 12. Filter accuracy
4-11 Check step 13. lnput monitor.
..............................
7
Orientation and disassembly of multipin
connectors
Side cover removal or replacement
Top and rear panel removal
Screws attaching the board assemblies tothe
plug-in frame
Rear interface connector assignments
Adjustment location illustration for Main,
lnput and Notch dvm boards.
Adjustment location illustration for Control
and IMD Option boards.
lnput board
Main board
Logic board
Dvm board
Display board
IMD option board
8
and adjustment step
8.
SMPTE
......
11A and adjustment step 11A.
.........
.........
........
.........
..........
.......................
.....
...........
.....................
(A14) parts location grid.
(A15) parts location grid.
(A12) parts location grid.
(A1 1) parts location grid.
(A10) parts location grid.
(A13) parts location grid.
...
.
.
...
Page
Scam
by
ARTEK
MEN
=r
LIST
OF
TABLES
Table
No.
Electrical Characteristics
Environmental Characteristics
Physical Characteristics
Gains from INPUT terminals to FUNCTION
OUTPUT connector for various settings of
the INPUT LEVEL RANGE control
Truth Table for U1400 Outputs 3-4
Internal Connections in
Logic States of pins 10 and 11
GainandSwitchingthroughU1210
Suggested Test Equipment
Common Mode Rejection Check
Level Function Accuracy
Relative Susceptibility to Static Discharge
Damage..
The following lables are located in the diagrams
foldout section at the rear of this manual.
lnput Board (A14) Component Reference
8-1
Chart.
8-2 lnput Board (A14) Component Reference
Chart.
8-3 Main Board (A15) Component Reference
Chart.
8-4 lnput Board (A14) Component Reference
Chart.
.......................
NOTE
.............
.........
.............
......
........
U1000 Depending on
.........
.....
..........
.......
.............
Page Table
N 0.
1-2
1-6
1-7
2-13
3-4
3-4
4-1
4-6
4-6
5-1
8-5
8-6 Main Board
8-7
8-8 Dvm Board (All) Component Reference
8-9 Display Board
8-10 Logic Board
8-11 Logic Board
8-12 Logic Board
8-13 Main Board (A1 5) Component Reference
8-14 IMD Option Board
lnput Board
Chart.
Chart.
Logic Board
Chart.
Chart.
Chart.
Chart.
lnput Board
Chart.
Main Board
Chart.
Chart.
Chart.
Chart.
Reference Chart.
(A14) Component Reference
(A15) Component Reference
(A12) Component Reference
(A12) Component Reference
(A14) Component Reference
(A15) Component Reference
(A12) Component Reference
(A12) Component Reference
Page
(A10) Component Reference
(A13) Component
OPERATORS SAFETY SUMMARY
The general safety information in this part of thesummary
is for both operating and servicing personnel. Specific
warnings
manual where
s~lmmarv.
-
-
.
. . .
. . -.
,
and
cautions
they apply, but may not appear
.
will
be
found
throughout
in
the
this
TERMS
In This Manual
CAUTION Statements identify
could result in damagetotheequipment or other property,
WARNING
that could result in personal injury or loss of life.
As Marked on Equipment
CAUTION indicates a personal injury hazard not immediately
hazard to property including the equipment itself.
DANGER indicates a personal injury hazard immediately
accessible as one reads the marking.
accessible as one reads the marking, or a
conditionsor practicesthat
identify conditions
or
practices
Power Source
This product is intended to operate from a power module
connected to a Power source that will not apply morethan
250
volts rms between the supply conductors or between
either supply conductor and ground. A protective ground
connection by way of the grounding conductor in the
power cord is essential for safe operation.
Grounding the Product
This product is grounded through the grounding conduc-
tor of the power module power cord. To avoid electrical
Shock, plug the Power cord into a properly wired recep-
tacle
before
terminals. A protective ground connection by way of the
grounding conductor in the power module power cord is
essential for safe operation.
'Onnecting
the
product input
Or
Output
Danger Arising From Loss of Ground
Upon loss of the protective-ground ~~nnection, all
accessible conductive parts (including knobs and controls that may appear to be insulating) can render an
electric
SYMBOLS
In This Manual
symbol indicates where applicable
This
cautionary or other information is to be
found.
As Marked on Equipment
9
DANGER - High voltage.
@
Protective ground (earth) terminal.
ATTENTION
-
refer to manual.
Use the Proper Fuse
To avoid fire hazard, use only the fuse of correct type,
voltage rating and current rating as specified in the parts
list for your product.
Refer fuse replacement to qualified service personnel.
DO
NO^
Operate in Explosive Atmospheres
To avoid explosion, do not operate this product in an
explosive atmosphere unless it has been specifically
certified for such operation.
Do Not Operate Without Covers
To avoid personal injury, do not operate this product
without covers or panels installed. Do not apply power to
the plug-in via a
plug-in.extender.
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SERVICE SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL ONLY
Refer also to the preceding Operators Safety Summary.
Do Not Service Alone
Do not perform internal service or adjustment of this
product unless another person capable of rendering first
aid and resuscitation is present.
Use Care When Servicing With Power On
Dangerous voltages may exist at several points in this either supply conductor and ground.
product. To avoid personal injury, do not touch exposed connection by way of the grounding conductor in the
connections and components while power is on. power cord is essential for safe operation.
Disconnect power before removing protective panels,
soldering, or replacing components.
Power Source
This product is intended to operate in a power module
connected to a power source that will not apply more than
250
volts rms between the supply conductors or between
A
protective ground
Scans
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TEK
MEDL4
vii
=>
~lrkvpr
MAX
+
AA501
Distortion
Analyzer
r
-RMs
L
AVC
1
rn
"1
f:~~R
r
viii
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ARTEK
MEDIA
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SPECIFICATION
Instrument Description
The AA 501 is a fully automatic distortion analyzer,
packaged as a two-wide
distortion is measured with the standard instrument. Option
01 instruments also measure
distortion and
tion. Option 02 instruments permit noise measurements in
45405.
Distortion set level, frequency tuning and nulling are
fully automatic, requiring no operator adjustment. Input
level range and distortion measurement range selections
are fully automatic or may be manually selected. Distortion readout is provided in percent or dB.
The
audio frequency voltmeter. Readings may be in volts,
dBm, or dB relative to any arbitrary reference.
Filters are included which allow measurement of noise to
IHF and FCC specifications. Option 02 instruments provide
a quasi-peak detector for noise measurements in accordance with
provided as are provisions for external filters.
All readings are displayed on a
uncalibrated analog readout is also provided to aid in nulling
and peaking applications.
Ac to dc conversion is either average or true rms re-
sponding, allowing conformance with most standards.
CClF two-tone difference frequency distor-
with
CC'R
AA
501 is also a high sensitivity, autoranging,
CClR or DIN standards. A hum rejection filter is
TM
500 plug-in. Total harmonic
SMPTEIDIN intermodulation
468-2
3
112 digit readout. An
Or
Op-
tion 02 instruments provide quasi-peak or true rms
detection. This feature
obtained
the
on
other
Ac input and output connections are available on both
front
respondingtothedisplayed
therearinterface.
with other instruments such as filters, chart recorders,
spectrum analyzers, oscilloscopes, etc.
'permits comparison with readings
instruments.
and
the
rear
interface.
reading,
Thisallowsflexibilityininterconnection
Dc
signals,
areavailablethrough
tor-
Performance Conditions
The electrical characteristics in this specification are
AA
valid only if the
temperature between
must be in a noncondensing environment
described under the
minutes warm-up time for operation to specified ac-
curacy; sixty minutes after exposure to or storagein a high
humidity (condensing) environment. Any conditions that
are unique to
stated as part of that characteristic.
The electrical and environmental performance limits,
together with their related validation procedures, com-
prise a complete statement of the electrical and en-
vironmental performance of a calibrated instrument.
Items listed in the Performance Requirements column
of the Electrical Characteristics are verified by completing
the Performance Check in the Calibration section of this
manual. ltems listed in the Supplemental Information
column are not verified in this manual.
501 has been adjusted at an ambient
+20° C and +30° C. The instrument
whoselimits are
environmental part. Allow twenty
a
particular characteristic are expressly
REV
NOV
1981
SCMS
by
ARTEK
MEDLQ
=>
-
--
-
-
--
-
--
-
Characteristics
.-
-
-
- - -- - -
INPUT (all functions)
Impedance
----
-
.
-
-
Maximum Input voltage
-
Common mode rejection
(inputs shorted)
-
-
--
- -
LEVEL FUNCTION
Table
1-1
7-
--
-.
-
-
--
Performance Requirements
.
--
ELECTRICAL CHARACTERISTICS
-
--
-
r
Supplemental Information
-
-
--
--
--
-
-
-
-.
,
100
kR,
+
2%, each side to ground
200
pV to 200 V in 10 steps (2-6 se-
quence from 200
-
--
-
--
250 dB at 50 or 60
mV to 200 V)
~
---
~-
--
Hz
--
for common
mode signals up to one-half of selected
input range or 50
mV, whichever is
greater.
Full differential. Each side ac coupled
through
1
pF
and shunted to ground by
100 pF. Dual banana jack connectors at
0.750 inch spacing with ground connector
additionally provided.
--
-
-.
-
Range selection is manual or automatic.
Auto-ranging time is typically
(1
second.
Separate increase range and decrease
range indicators illuminate whenever input
level does not fall within optimum window
for selected range. For specified instrument performance both indicators must
be extinguished.
-
-
- - --
. . -.
300 V peak, 200 V rms either input to
ground or differentially. Will recover without damage from continuous overloads of
120
V
rms or 200 V rms for 30 minutes on
all ranges. For linear response peak input
voltage must not exceed 3 times INPUT
LEVEL RANGE setting.
~~
~~
~
Typically 240 dB to 300
kHz.
=
Modes
-
--
Accuracy (V,, a 100 pV
with level ranging indicators
extinguished)
20
Hz
-
to 20
kHz
-
---
Volts
Within
+
2%
I
I
1
(
Volts, dBm (600
0).
or dB ratio with push
to set 0 dB reference. lnput range determines display range. Single effective
range in dB modes with 0.1 dB resolution.
Stored
subsequent changes in mode or function.
-
0 dB reference is unaffected by
-.
On the 200 pV range accurcy above
50
kHz
is +4%, -6% (+0.5 dB,
-0.7 dB). Accuracy with quasi-peak re-
sponse (Option 02 only) is valid from
20
Hz
to 50
kHz
only).
REV
NOV
1981
1-1
Table
-
(cont)
Performance Requirements
- - -
--
- - -
-
-
At least 300 kHz with no filters
selected.
-
-
-
--
Supplemental Information
--
Residual noise
(Source resistance
-
G
1 kS1)
TOTAL HARMONIC DISTORTION
PLUS NOISE FUNCTION
Fundamental frequency
range
Minimum input level
Distortion ranges
--
Accuracy (THD ~30%
and readings 34% of
selected distortion range)
~3.0 rV
(-
108 dBm) with 80 kHz,
400 Hz filters and rms response
~1.5pV (-114dBm) with A
weighting filter and rms response
(standard and Option 01 instruments
only)
~5.0 wV
(-
104 dBm) with CClR
weighting filter and quasi-peak response (Option 02 only)
-
--
- - -
-.
10 Hz to 100 kHz
Fully automatic tuning and nulling. For
proper tuning
THD+ N <1O0/0. After initial
tunlng THD+ N can degrade to 30% without loss of lock for
nulling
time is less than 5 s above 20 Hz.
-
SINAD testing. Typical
--
-
-
Autorange, 20°/0, 2%, 0.2%, and dB. dB is
internally autoranging with single effective
display range. Autorange allows measurements above 20%.
+
Accuracy is limited by residual THD
N
and filter selection. Not applicable with
quasi-peak response (Option
02 only).
20 Hz to 20 kHz
10 Hz to 100 kHz
-
---
Residual
THD+N (V,,, a250 mV,
source resistance G 1 kS1)
20 Hz to 20 kHz with
80 kHz noise limiting filter
<+40°C
and T
10Hz to50kHz
50 kHz to 100 kHz
Typical fundamental
rejection
REV
NOV
1981
Within
Within
--
for harmonics
- - -
<
100 kHz.
+
10%
(k
1 dB) for harmonics
+lO%, -30%
~300 kHz.
- - -
- - -
(+ 1 dB,
--
-3
dB)
-
-
-.
-
- - -
SG
Measured with
505 oscillator. All dis:ortion, noise, and nulling error sources
:ombined.
~0.0025~/0 (-92 dB) average
response
~0.0032% (-90 dB) rms response
=z0.0071
=zO.OIOO/~
O/O
(-83 dB), rms response
(-
80 dB), rms response
it
least 10 dB below specified residual
rHD
+
N
or the actual signal THD, which-
!ver is greater.
~cMs
by
ARTEK
MEDL4
=,
--
.-
Characteristics
- - -
-
-.
-
-
-
INTERMODULATION DISTORTION
FUNCTION
Table
1-1
(cont)
-
Performance Requirements
-
---
-
--
-
-
--
-
--
-
-
Supplemental lnformatlon
-
--
--
--
Operation
SMPTE and DIN tests
Lower frequency range
Upper frequency range
Level ratio range
Residual IMD
(V, 2250 mV,
source resistance 61 kil,
~40°C)
.-
~
CClF difference tone test
(IM components
G
Frequency range
Difference frequency range
Residual IMD
(Vn a250 mV,
source resistance 6 1 kR,
<+40°C)
Minimum input level
-
-~
~~
-
-
~
Accuracy (IMD ~30% and
readings
distortion range)
---.
~.~
>4% of selected
-~
FILTERS
1 kHz)
Fully automatic SMPTE, DIN, or CClF difference tone tests depending upon actual
input signal whenever respective IMD
620%. Distortion ranges are same as
THD
t
N function.
-.
- - -
50 Hz to 250 Hz
3
kHz to 100 kHz
:
1
to 5: 1 (lower : upper)
1
~0.0025% (-92 dB) for 60 Hz-7 kHz
or 250 Hz-8 kHz, 4: 1 signals,
-
response
rms
4 kHz to 100 kHz
80 Hz to 1 kHz
~0.0018% (-95 dB) with 14 kHz and
15 kHz,
Within
rms
k
10%
response
(i
1 dB)
-
-
.
-
Accuracy is limited by residual IMD and
filter selection. Not applicable with quasi-
~
peak response (Option 02 only)
400 Hz high pass
~~~
80 kHz low pass
~
.
30 kHz low pass
(standard and Option 01
only)
~
-
-~
-
22.4 Hz-22.4 kHz
{Option 02 only)
-~
-
~~~-.~ ~ -~.~ - .~
A weighting (standard and
Option 01 only)
~ ~
~
~
CClR WTG (Option 02 only)
-3 dB at 400 Hz,
+
5%; at least
-40 dB rejection at 60 Hz
-3 dB at 80 kHz,
-3
dB at 30 kHz, k 5%
-3
dB at 22.4 Hz, + 5% and
22.4 kHz,
+-
Scans
5%
by
_+
5%
ARTEK
MEDL4
=>
3
pole Butterworth response
-.
- - --
3
pole Butterworth response
3
pole Butterworth response
--
.-
Nithin specifications of CClR Recommenjation 468-2 and DIN 45405 for
~nweighted measurement response.
Nithin specifications for type 1 sound lev?I
meters listed in ANSI S 1.4 1971 (re-
lised 1976) and IEC Recommendation
179.
-
-
Nithin specifications of CClR Recommeniation 468-2 and DIN 45405 for noise
neasurements. Functional only with quaii-peak detector (response).
-
-
-
-
.
- - -
-
--
REV
NOV
1981
Table
1-1
(cont)
Performance
--
-
--
Requirements
-
-- . - - -
-
-
-
---
-
Supplemental Information
-
.
--
-
--
- - -
-
-
---
-
Auxiliary
-
--
-
-
-
.-
FRONT PANEL SIGNALS
MONITOR OUTPUT
lmpedance
FUNCTION OUTPUT
Signal
Sensitivity
Maximum
Input Voltage
Selects front panel AUXILIARY INPUT alowing connect~on of external filter be-
-
--
-
-
-
1 V rms, k 10%
ween lt and FUNCTION OUTPUT.
-
-
-
- - -
-
-
Constant amplitude (average response)
version of differential input signal. THD is
typically
20
Hz
~O.OOIOO/~
to 20 kHz.
(-
100 dB) from
Approximately 20 times input signal.
1
V,
+-
3%,
for 1000 count volts or
display.
+-
3%, for 1000 count volts or
1 V,
display.
Selected and filtered ac signal actually be-
O/O
ing measured.
Loop-through accuracy from FUNCTION
O/O
IS
t
OUTPUT
3%.
15 V peak, 6 V peak for linear response.
lmpedance
DETECTORS AND DISPLAYS
Detectors (Response)
RMS
AVG (standard and
Option
Q-PK
01)
-
- - - - -
(Opt~on 02 only)
- - - - -
Ac coupled.
True rms detection.
- - - - -
-
- - -
-
-
Average detection, rms calibrated for
sinewaves. Typically reads 1 to 2 dB lower than true rms detection for noise,
THO+
N,
-.
-.
--
and IMD measurements.
~
~
Quasi-peak detection, rms calibrated for
sinewaves. Within specifications of
CClR
Recommendation 468-2 and DIN 45405.
Due to the peak hold nature of its response readings considerably higher than
rms response will occur with large crest
factor signals such as noise. The input
range indicators should be ignored and
auto-ranging avoided with these types of
signals.
REV
NOV
1981
Scans
by
ARTEK
MEDU
=,
--
~
Displays
Digital
~
Characteristics
~
--
~
--
--
I
Table
1-1
--
(cont)
-
.
--
--
3
112 digit, 2000 count
LED.
Overrange in-
--
Performance Requirements Supplemental Information
dication is 1, blank, blank, blank.
--
Analog bar graph
MISCELLANEOUS
Power consumption
Internal poker supplies
+5
-.
-
-
Fuse Data
Recommended adjustment
interval
Warm-up time
10 segment LED intensity modulated bar
graph display of digital readout. Seg-
ments are logarithmically activated with
approximately 2.5
--
-.
-
I
224
-
-
.
watts
Nominally + 15.1
Nominally - 15.1
--
-
Nominally +5.0
3
AG,
1
A,
3
AG,
1
A,
3
AG,
1
A,
-
-
-- --
-.
250
250
250
dBIsegment.
-
-
- - - . - - -
V,
k
3%
V,
k
5%
V,
+
-.
V,
fast blow
V,
fast blow
V,
fast blow
--
5%
- - --
- - -
-
-
-
-.
--
1000 hours or 6 months whichever occurs
first
20 minutes (60 minutes after storage in
high humidity environment)
-
-
-
cons
by
ARTEK
MEDIA
=.>
REV
NOV
1981
Table
1-2
ENVIRONMENTAL CHARACTERISTICSa
..~
Characteristics
-
--
-
.
.
--
. .
Temperature Meets MIL-T-28800B, class 5.
.
i
ppppp.-----
Description
Operating
Humidity
--
Altitude
Operating
Non-operating
-
- - - . -
-
Vibration
- --
-
95% RH,
45% RH, to t-50°C
0°C to +40°C
-
4.6 km (1 5,000 feet)
15 km (50,000 feet)
.
Exceeds
----
-
Exceeds MIL-T-28800B, class 5.
p-
- . --
Exceeds MIL-T-28800B, class 5, when
MIL-T-28800B, class 5
~~
installed in qualified power modulesb.
0.38 mm
(0.015") peak-to-peak, 5 Hz
to 55 Hz, 75 minutes.
MIL-T-028800B, class 5, when
Shock
Meets
installed in qualified power modulesb.
30 g's
(112 sine) 11 ms duration, 3
shocks in each direction along 3 major
axes. 18 total shocks.
-
Bench handlingC
-.
~-
~
~~
.. - .
EMC
Electrical discharge
----
-
-
.With power module.
b~efer to
TM
500
power module specifications.
=Without power module.
Meets
MIL-T-28800B, class 5.
12 drops from
45@. 4" or equilibrium,
whichever occurs first.
Qualified under National Safe Transit Association Preshipment Test Procedure
B-1 and 1A-B-2.
Within limits of MIL-461A.
20 kV maximum charge applied to instrument case.
I
.. . . - . . .
.
-
..
-
-
.
.
1A-
REV
NOV
1981
Scans
by
ARTEK
MEDL4
=>
Characteristics
.
-~
-~-.
~
-.~~- . --
-
-
~-
Maximum Overall Dimensions
1-3
Table
PHYSICAL CHARACTERISTICS
p--.---p-----.---.-
-..
-
Description
.. - . - -.
~-
-
.
---
---
-~
~
Height
Width
Length
-
Net Weight
-
--
Finish
Front Panel
- - --
--
126.0 mm (4.96 inches)
131.2 mm (5.1 6 inches)
(1
-.
285.5 mm
~1.7
1.24 inches)
kg (3.75 Ibs.)
Plastic-aluminum laminate
Anodized aluminum
Scam
by
ARTEK
MEDL4
-->
@
NOV
1981
OPERATING INSTRUCTIONS
Section
2-AA
501
Preparation For Use
The AA is calibrated and
received. It operates in any two compartments of a
TM 500-Series power module. See the power module
instruction manual for line voltage requirements and
power module operation. Figure
installation and removal procedure.
Turn the power module off before inserting the
AA
501.
Otherwise, arcing may occur at the rear
interface connectors, reducing their useful life and
damage may result to the plug-in circuitry.
Check to see that the plastic barriers on the
connecting jack of the selected power module compartment match the cutouts in the AA 501 circuit board edge
2-1
shows the AA 501
use
when
inter-
connector. Align the AA 501 chassis with the upper and
lower guides of the selected compartment. Press the
AA 501 in, to firmly seat the circuit board in the inter-
connecting
To remove the AA 501 pull the release latch (located in
the lower left corner) until the interconnecting jack
disengages and the AA 501 slides out.
Check that the AA 501 is fully inserted in the power
module. Pull the power switch on the power module. One
or more characters in the
visible.
jack.
LED
display should now be
Repackaging Information
If the Tektronix instrument is to be shipped to a
Tektronix Service Center for service or repair, attach atag
Fig.
Scans
2-1.
Installation and removal.
by
AR
TEK
MEDL4
=>
ENGLISH
2-1
Operating Instructions-AA 501
showing the owner (with address) and the name of an
individual at your firm that can be contacted. Include the
complete instrument serial number and a description of
the service required.
Save and reuse the package in which your instrument
was shipped. If the original packaging is unfit for use or
not available, repackage the instrument as follows:
Surround the instrument with polyethylene sheeting to
protect the finish of the instrument. Obtain a carton of
corrugated cardboard of the correct carton strength
and having inside dimensions of no Iessthan six inches
more than the instrument dimensions. Cushion the
instrument by tightly packing three inches of dunnage
or urethane foam between carton and instrument on all
sides. Seal the carton with shipping tape or an in-
dustrial stapler.
The carton test strength for this instrument is 200
pounds per square inch.
Controls, Connectors, and Indicators
All controls, connectors and indicators (except for the
rear interface connector) required for operation of the
AA 501 are located on the front panel. Figure2-2 provides
a brief description of all front panel controls, connectors,
and indicators.
@
@
@
@
@
Release Latch
LEVEL
Button in selects input level measuring function.
VOLTS
Button in selects voltage units for level function.
Button in selects
n)
600
dB
Button in selects dB ratio, with respect to preset
level, as units for level function.
PUSH TO SET 0
Push button to set display to 0 with input signal
applied to INPUT terminals in LEVEL function.
dB RATIO and LEVEL pushbuttons must be in for
this feature to operate.
units for level function.
RATIO
dBm (reference is 1 mW into
dB
REF
@
@
@
@
@
INPUT LEVEL RANGE
Selects input voltage range or AUTORANGE.
The three most sensitive ranges operate in the
LEVEL FUNCTION only.
DECREASE RANGE
When this light is illuminated, reduce the INPUT
LEVEL RANGE until the light goes out.
INCREASE RANGE
When this light is illuminated, increasethe INPUT
LEVEL RANGE until the light goes out.
INPUT
Differential input terminal. Positive going input
signal provides positive going output signal at
INPUT MONITOR.
INPUT
Differential input terminal. Negative going input
signal provides positive going output at INPUT
MONITOR.
@
REAR INTFC-INPUT
Button in selects rear interface input; button out
selects front panel input.
@
RESPONSE
Button in gives RMS detection (responds to the
rms value of the input waveform). Button out
gives average detection (rms calibrated for
si newaves).
Button in selects total harmonic distortion
FUNC-I-ION.
@
IMD (Option 01 instruments only)
Button in selects intermodulation distortion func-
tion.
@
AUTO RANGE
Button in selects automatic distortion range
selection (0.2% to 100% full scale).
Scans
by
ARTEK
MEDL4
=>
Operating Instructions-AA
501
REV
NOV
1981
Fig. 2-2. Front panel controls and connectors.
Scans
by
AR
TEK
MEDIA
=>
2958-1
ENGLISH
3A
2-3
Operating Instructions-AA 501
@
20% AUXILIARY INPUT
Button in selects full scale distortion readout of Provides input to the detector circuit when the
20% with 0.01% resolution.
Button in selects full scale distortion readout of
2% with 0.001% resolution.
Button in selects full scale distortion readout of digital display for nulling and peaking. Each
0.2% with 0.0001% resolution.
@
dB
Selects single equivalent 0 dB to -100 dB distor-
tion display range with 0.1 dB resolution.
@
400 Hz HI PASS
Button in connects filter before detector circuit in
all functions.
EXT FILTER button is pressed.
@
Ground
Provides front panel chassis ground connection.
LED Bar Graph
Provides approximate analog display of the
segment represents about 2.5 dB.
@
Digital Display
3
1/2 digits. Overrange indication is a blanked
display with the numeral 1 in the most significant
digit position.
@
VOLTS
llluminated when display units are volts.
@
@
80 kHz LO PASS
Button in connects filter before detector circuit in
all functions.
@
30 kHz LO PASS
Button in connectsfilter beforedetector circuit in
all functions.
@
'A'
WEIGHTING
Button in connects filter before detector circuit in
all functions.
@
EXT FILTER
Button in allows connection of external filter
between FUNCTION OUTPUT and AUXILIARY
INPUT in all functions.
Instrument Connections
INPUT MONITOR
Provides a sample of the input signal.
@
FUNCTION OUTPUT
Provides a sample of the selected FUNCTION the rear interface signal input press the INPUT pushbut-
signal. ton.
Connections can be made to the rear interface connector.
However, due to possible crosstalk, low level or distortion
measurements made through the rear interface may be
degraded. To measure signals connected to the front
panel make certain the INPUT pushbutton is out.
mVOLTS
llluminated when display units are millivolts.
@
pVOLTS
llluminated when display units are microvolts.
llluminated when display units are percent.
@)
dBm
Illuminated when display units are
@
dB
Illuminated when display units are dB.
To make connections to the AA 501, refer to Fig. 2-3.
dBm.
Toselect
Scans
by
ARlEK
MEDIA
=>
SG
505
Oscillator
AA501
Dlstortlon Analyzer Oscilloscope
Operatlng
Shielded twlsted pair
Instructions-AA
501
Fig.
2-3.
Typlcal connectlons for distortlon measurements. See text.
300
V
Maximum front panel input voltage is
200
V
rrns either input to ground or differentially.
42
V
Maximum rear interface input is
rms.
AA
The
cidental overloading. This circuitry will recover without
damage from continuous 120 V rms (30 minutes at 200 V
rms) overloads in any INPUT LEVEL RANGE setting.
In most cases, for maximum hum rejection, follow the
cabling and grounding as shown in the figure. Shielded,
twisted pair offers maximum hum and radio frequency
interference rejection. Cable shielding, if used, should be
grounded only at the AA 501 front panel ground post. Use
shielded cable to connect the output of an oscillator,
external to the device under test, to the input of the device.
Generally, if the device under test has one side of the input
grounded, float the output of the external oscillator to
avoid possible ground loops. If the input to the device
under test is floating (not chassis grounded) then select
the grounded mode for the output of the oscillator.
Terminate the output of the device under test in its
501 input circuitry is protected against ac-
peak and
peak,
30
V
2958-02
recommended load impedance, or the load impedance
specified in the appropriate standard.
The illustration shows an optional oscilloscope for
visual monitoring. If connected as shown in the illustration. channel 1 displays a sample of the input signal and
channel 2 displays the distortion components when in the
IM or THD+N function.
Level Measurements
In the LEVEL function the AA 501 operates as a wide
band ac voltmeter. The Specification section of this
manual contains operating parameters for this meter. The
meter is rms calibrated and either rrns or average responding, depending on the position of the RESPONSE
pushbutton.
Press the FUNCTION LEVEL pushbutton. The top
three buttons to the left of the FUNCTION pushbuttons
dBm
600
n,
select readout units as VOLTS,
An LED to the right of the display indicates the display
units. To measurevoltage press the VOLTS pushbutton. If
the INCREASE RANGE LED is illuminated, adjust the
INPUT LEVEL RANGE control to higher ranges until the
or dB RATIO.
ENGLISH
2-5
Operatlng Instructions-AA
501
LED goes out. If the DECREASE RANGE LED is illuminated, turn the INPUT LEVEL RANGE control
counterclockwise to a lower range until the DECREASE
RANGE LED goes out. For specified instrument accuracy
adjust the INPUT LEVEL RANGE as just described.
However, readings are usable as long as the display is not
overranged. Overrange is indicated by a blank display with
the numeral 1 in the most significant digit slot. If the
INPUT LEVEL RANGE switch is placed in the AUTO
RANGE position, the input level adjustment is ac-
complished automatically. The
or pVOLTS) automatically illuminate showing the proper
display units. Notice that the three most sensitive ranges
on the INPUT LEVEL RANGE control operate in the
LEVEL FUNCTION only.
When the
opposite
The reference level for this measurement,
dissipated in 600
developed across a 600
RANGEswitch operates in thesamemanner as previously
described.
The dB RATIO mode permits direct ratio meas-
urements of two input signal amplitudes. When the dB
RATIO pushbutton is pressed, the LED opposite the dB
nomenclature on the display is illuminated. To use this
feature, press the dB RATIO pushbutton. To establish the
input signal as
0 dB REF pushbutton and notice that the display reads all
zeros. As the amplitude of the input signal is changed, the
display will read the dB ratio of the input signal to the
reference signal amplitudes.
There are many useful applications for the dB RATIO
mode in measurements of gain-loss, frequency response,
S/N ratio, etc. For example, the corner frequency of a filter
may be quickly checked. Set the test frequency to some
midband value and set the zero dB reference. Adjust the
test frequency until the display reads -3.0 dB; this is the
corner frequency of the
Gain measurements may be similarly simplified by
using this feature. Set the device to be tested as desired
and connect the AA 501 input to the input of the device
under test. Press the PUSH TO SET
Connect the input of the AA
read the gain or loss directly from thedisplay. When using
the SG 505 oscillator and the TM 500 rear interface
feature, changing of external connections to establish the
0 dB input level reference is not necessary. Interconnect
the Buffered Main Output of the SG 505 and the rear
interface input of the AA 501. Pressing the REAR
pushbutton will conveniently allow direct measurement of
the signal level going to the input of the device under test.
dBm 600
dBm on the display indicates the display units.
0 dB reference, push the PUSH TO SET
f2
f2.
This is equivalent to 0.7746 V rms
fllter.
LED'S (VOLTS, mVOLTS
pushbutton is pressed, the LED
0 dBm, is 1 mW
C2
resistor. The INPUT LEVEL
0 dB REF pushbutton.
501
to the device output and
INTFC
When measuring signal to noise ratio or making noise
level measurements, it is often desired to employ a
frequency dependent weighting network. The AA 501
provides several internal filters as well as facilities for
connecting external filters. For information on their
operation and use, see the text under Filtersin thissection
of the manual.
Dlstortlon Measurements
Distortion is a measure of signal impurity. It is usually
expressed as a percentage or dB ratio of the undesired
components to the desired components of a signal.
Harmonic distortion
ly related or integral multiples of
the fundamental, and can be expressed for each particular
harmonic. Total harmonic distortion, or THD, expresses
the ratio of the total power in all significant harmonics to
that in the fundamental.
A distortion analyzer removes the fundamental of the
signal to be investigated and measures the remainder. See
Fig.
2-4. Because of the notch filter response, any signal
other than the fundamental will influence the measure-
A
ment.
inevitably include effects from noise or hum. The term
THD+N has been recommended' todistinguish distortion
measurements made with a distortion analyzer from those
made with a spectrum analyzer. A spectrum analyzer
allows direct measurement of each harmonic. However, it
is relatively complex, time consuming, and requires
interpretation of a graphic display.
All distortion analyzers are limited ultimately by their
internal distortion and noise. Traditionally, distortion
analyzer residual noise and distortion have been specified
separately. However, because an actual measurement
always includes both effects, both residuals must be
combined to determine the minimum valid reading. For
example, an analyzer rated at 0.002% residual distortion
and 0.002% noise may exhibit a
0.0028% and still be within specification. Also, average
responding analyzers may read up to
rms responding analyzers. The AA 501 specifies the
combined residual effect with rms response and offers
selection of rms or average response.
Distortion analyzers can quantify the nonlinearity of a
device or system. The transfer (input vs output)
characteristic of a typical device is shown in Fig. 2-5.
Ideally this is a straight line. A change in the input
produces a proportional change in the output. Since the
actual transfer characteristic is nonlinear, a distorted
'
IHF-A-202 1978. Standard Methods of Measurement for Audio
Ampllflers. The Institute of High Fidelity, Inc., 489 Fifth Avenue.
New York, N.Y. 10017
total harmonic distortion measurement will
issimply the presence of harmonical-
a
single pure tone called
THD+N reading of
25% lower than true
ENGLISH
2-6
-
Fig.
2-4.
Block dlagram of a baslc harmonlc dlstortlon analyzer.
version of the input waveshape appears at the output. The
output waveform is the projection of the input sine wave
on the device transfer characteristic as shown in Fig.
2-6.
The output waveform is no longer sinusoidal, due to the
nonlinearity of the transfer characteristic. Using Fourier
series it can be shown that the output waveform consists
of the original input sine wave, plus sine waves at integer
multiples of the input frequency. These harmonics represent nonlinearity in the device under test. Their
amplitudes are related to the degree of nonlinearity.
Distortion Measurement Procedure
All of the controls found on a traditional distortion
analyzer areautomated on the
to set the INPUT LEVEL RANGE and distortion range
switches to AUTO RANGE, press
for a reading. Minimum input signal amplitude for distortion measurements is 60
the instrument may be manually operated as described in
the following paragraphs.
AA
mV. To
501.
It isonly necessary
THD+N and wait briefly
providegreaterflexibility
-
-
A
Output
Fig. 2-5. Transfer characterlstlcs of an audio device.
4
0
2958-04
REV
NOV
1981
Scum
by
ARTEK
MEDU
ENGLISH
2-7
Operating
Instructions-AA
501
A
Actual
transfer
characterlstlc
/
Actual Ideal
Output output output
/
/
1
/
/
/
/
Fig.
2-6.
Input
THD
test of transfer characterlstlcs.
lnput
'.be/
/
2958-05
-
Adjustment of the input level range control is the same
as for level measurements. Manually setting the INPUT
LEVEL RANGE control to the correct scale ensures that
10
to
12
the input is within the
derangeof theinternalauto
set-level circuitry. The range lights must be extinguished
200
to make readings to specified accuracy. The
and
20
mV ranges do not operate in the distortion
pV, 2 mV
function.
To manually select a distortion range, press the
THD
tN button and the desired range button. Selection of
AUTO RANGE causes the instrument to autorange the
distortion readout. The remaining range pushbuttons
cause the instrument to stay in these ranges without
autoranging. This can reduce the measurement time
slightly if the approximate reading is already known. This
is useful in production line testing or in the testing of low
distortion equipment.
ENGLISH
2-8
ThedB display iseffectively asingle
range; however, internal instrument operation is identical
to AUTO RANGE.
When making distortion measurements, the
RESPONSE button should normally be in the RMS
position. Current distortion measurement standards re-
quire the use of rms reading instruments by specifying
power summation of each of the components. The AVG
mode may be used when making comparisons with
readings taken with traditional distortion analyzers.
However, it may read up to
25% (2
dB) lower than rms
response.
For frequencies below
measurement may be improved by activating the
LO PASS filter.
If
'20
kHz the residual noisein the
80
kHz
hum (line related components) are
interfering with the measurement, they may be removed
Operating Instructions-AA
501
with the 400 Hz HI PASS filter. This filter should not be
employed at frequencies below 1 kHz as erroneous
readings will result. For more information see text under
Filters in this section of this manual.
A distortion analyzer must tune out the fundamental
frequency. In the AA 501 all tuning of frequency is done
automatically. For input signals with greater than about
20% noise and distortion, care must be taken to ensure
proper locking of thiscircuitry. Inmost applications which
require higher distortion measurements (for example,
SINAD' testing) the circuitry remains locked after it is
initially given a clean signal. To perform a
receiver under test is first given a high level input. The
AA 501 will lock onto the audio signal at theoutput. Therf
level feeding the receiver is then reduced until a 712 dB
distortion reading is obtained on the AA 501.
'
Defined in Electronic Industries Association Standard No.
RS
204A, July 1972, Electronic Industries Association,
Engineering Department, 2001 Eye St. N.W., Washington, D.C.
20006.
SlNAD test, the
IM Distortion Measurements (Option
Another measurement of distortion is the interaction of
two or more signals. Many tests have been devised to
measure this interaction. Three standards are
DIN4, and CCIF'. The Option 01 AA 501 is capable of
automatically selecting and performing all three tests.
To measure intermodulation distortion (IM), according
to SMPTE and DIN standards, the device under test is
excited with a low frequency and high frequency signal
simultaneously (Fig. 2-7). The output signal is high-pass
filtered to remove the low frequency component. The high
frequency tone is then demodulated, as an AM radio
signal. The demodulator output is low-pass filtered to
Society of Motion Picture and Television Engineers, Standard
No. TH 22.51, 862 Scarsdale Avenue, Scarsdale, N.Y. 10583.
Deutsches lnstitut fur Normung e V, No. 45403 Blatt 3 and 4,
January 1975, Beuth Verlag GmbH, Berlin 30 and Koln 1.
'
International Telephone Consultative Committee.
01)
SMPTE~,
High Frequency
Oscillator
-
Fig. 2-7. Block diagram of basic IM analyzer.
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2-9
Operating Instructions-AA
remove the residual carrier (high frequency) components.
The amplitude of the low frequency modulation is displayed as a percentage of the high frequency level.
As shown in Fig. 2-8, when this composite signal is
applied to the device, the output waveform isdistorted. As
the high frequency tone is moved along the transfer
characteristic, by the low frequency tone, its amplitude
changes. This results in low frequency
tion of the high frequency tone. This modulation is
apparent in the frequency domain as sidebands around
the high frequency tone. The power in these sidebands
represents nonlinearity in the device under test.
The amplitude ratio of low to high frequencies should
be between
ly adjusts calibration to compensate for the selected test
signal ratio. Some additional range is provided in this
circuitry to enable measurement of devices with nonflat
frequency response.
4.1 and 1.1. The AA 501 circuitry automatical-
501
amplitudemodula-
7
SMPTE standard test frequencies are 60 Hz and
The DIN standard is virtually identical to the SMPTE
standard except for the two frequencies used. They may
be any pair of octave band center frequencies, with the
upper at least eight times as high as
8 kHz are common). The AA 501 can accept a wide range
of test frequencies as shown in the Specification section.
CCIF difference frequency distortion is measured with
two high frequency sine waves driving the device under
test. Both are of equal level and closely spaced in
frequency. Nonlinearities in the device under test cause
the sine wavesto cross modulate. This creates new signals
at various sum
For example, the commonly used 14 kHz and 15
frequencies produce 1 kHz, 13 kHz, 14 kHz, 15 kHz,
16 kHz, 28 kHz, etc. Ideally, one would measureeach new
component with a tunable filter such as a spectrum
analyzer. However, this is usually limited to an 80 dB
dynamic range and is very tedious, Agood measureof this
anddifferencefrequenciesfrom
thelower (250 Hzand
kHz.
theinputs.
kHztest
-
Transfer (input-output)
characteristics of
test device
I
ENGLISH
2-10
Fig.
2-8.
IM
test of transfer characteristics in time and frequency domain.
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Operating Instructions-AA
501
distortion may be obtained by measuring only the
difference frequency (in this example 1 kHz). If only the
low frequency component is measured, it is called a CClF
second order difference frequency distortion test.
To measure two tone difference frequency distortion
the device is excited with two input signals as described
above. The output of the device is low-pass filtered to
extract the difference frequency. The level of this compo-
nent is expressed as a percentage of the high frequency
signals and is another measure of nonlinearity.
The AA 501 CCIF difference frequency mode will
accept any pair of input frequencies which are within
limitsas listed in
of the two signals should be equal.
IM
Distortion Measurement Procedure (Option
Intermodulation and THD testing aresimilar, using the
AA 501 (Option
signal source to the device under test, set the INPUT
LEVEL RANGE as described in the THD section. Press the
IMD FUNCTION button and select a distortion range.
Selecting AUTO RANGE or dB provides automatic ranging. The AA 501 accepts either a SMPTE,
difference frequency test signal. Selection between the
necessary analyzing circuits is accomplished
automatically.
There is a moveable jumper inside the AA 501 to allow
selection of SMPTE-DIN, CClF or automatic selection
between the two modes. Defeating the automatic test
selection circuitry is recommended if making
modulation distortion measurements greater than 20%.
Refer any jumper changes to qualified service personnel.
The
LO
will have little effect. The 400 Hz HI PASS and the 'A'
WEIGHTING filters will cause erroneous readings
because the
tests fall between 50 Hz and
activated in the
components being measured.
thespecification section. Theamplitudes
01)
01 only). After
PASS filters may beselected inthe IM mode but
IM components of interest generated by the
IM mode attenuate someof the frequency
connectingtheappropriate
DIN, or a CCIF
inter-
1
kHz. These filters, when
Filters
The five buttons along the right edge of the instrument
allow selection of four built-in frequency weighting filters
plus an external filter, as desired. See Fig.
curves of the various filters. The 400 Hz, 30 kHz and
80 kHz filters are all 3-pole (18 dB per octave
Butterworth alignment. They are placed in the measuring
circuitry immediately before the average or rms detectors.
These filters are functional in all modes of operation and
affect the signal at the FUNCTION OUTPUT connector.
2-9for response
rolloff)
Check the position of all filter pushbuttons before
making measurements to prevent inaccurate results.
Filtering takes place after all gain circuits. It is possible to
overload part of the instrument, when operating in the
manual distortion ranges with a filter selected, even
though the display is not overranged. This may be
checked by releasing the filter pushbuttons and checking
the display for overrange or by pressing the AUTO
RANGE pushbutton.
The 400 Hz HI PASS filter is used to reduce the effects
of hum on the measurement. Although the differential
input and common mode rejection of the AA 501 reduce
the effects of ground loops, extremely bad measurement
conditions may require use of this filter. The device under
test may also generate an undesirable amount of hum.
limiting the noise and distortion residuals obtainable. This
filter may be used when measuring level or harmonic
distortion of signals at about 1 kHz or greater. This filter
should not be used when measuring signals less than
1
kHz nor when measuring intermodulation distortion.
Use of the 80 kHz LO PASS filter reduces the effects of
wideband noise and permits measurement of lower
+N for input signals up to 20 kHz. For 20 kHz inputs, it
allows measurement of harmonics up to the fourth order.
Do not use this filter if harmonic components above
80 kHz are of interest. When checking noise the 80 kHz
filter may be used to reduce the measurement bandwidth.
However, for most noise measurements, the 30 kHz LO
PASS or 'A' WEIGHTING filters are recommended as they
correlate better with the perceived noise level.
The 30 kHz LO PASS filter provides bandwidth limiting
for broadcast proof of performancetesting. It is also useful
for unweighted noise measurements on audioequipment.
providing an equivalent noise bandwidth of 31.5 kHz.
When the 30 kHz filter is used, the 80
It may be desirable to modify the 30 kHz filter so that it
conforms to the 22.4 kHz IEC standard for audio noise
measurements. This may be performed by qualified
service personnel as described in the Service section of
this manual.
The 'A' weighting filter is used when measuring the
subjective noisiness of audio equipment. It conforms to
the noise measurement standards of the Institute of High
Fidelity (IHF). The filter shape is within ANSI, DIN, and
IECQtandards for class 1 sound level meters.
International Electrotechnlcal Commlssion. Publlcatlon
second edition, Precision Sound Level Meters,
Office of IEC (sales
Geneva
20
Switzerland.
department),
kHzfilter is disabled.
1,
rue de Varembe',
1973,
THD
179,
Central
1211
ENGLISH
2-11
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