HP 8903B Operation Manual
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Agilent Technologies. Inc
24001
E
Mission
Liberty
take, WA
99019
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Ag
i I en
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Technologies
Innovating
June
Dear Customer,
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semiconductor products, health care solutions, and chemical analysis became a new company,
Agilent Technologies. Now, many of your Hewlett-Packard products and services are in the care
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HP
8903B
2450A
AUDIO
(Including Option
ANALYZER
001)
Operation and Calibration Manual
SERIAL
This
manual applies directly to instruments with
serial numbers prefixed
to
2922A
For
numbers, refer
THIS
and all
additional important information about serial
MANUAL’’
Mqior
to
“INSTRUMENTS COVERED
in Section
NUMBERS
changes that apply
rev.ZOJUN91
1.
Fourth Edition
to
your
instrument.
BY
This
material may be reproduced by
Government pursuant
der the clause at
Copyright
EAST 24001
Operation and Calibration Manual HP Part 08903-90079
Other Documents Available:
Service Manual (Volume
Microfiche Operation and Service Manual HP Part 08903-90080
MISSION
1,
2)
HP Part 08903-90062
GHEWLETT-PACKARD COMPANY 1985
AVENUE, TAF C-34, SPOKANE, WASHINGTON, U.S.A. 99220
to
DFARS
the Copyright License
52.227-7013
or
for the
(AF’R
US.
un-
1988).
Printed in U.S.A. : November 1989
HEW
PACKARD
LETT@
1
Regulatory Information
(Updated
March
1999)
1
Regulatory
Safety Considerations
Information
(Updated
March
1999)
GENEFtAL
This product and related documentation must be reviewed for familiarization with safety
markings and instructions before operation.
This product has been designed and tested in accordance with
IEC
Publication
"Safety Requirements for Electronic Measuring Apparatus," and has been supplied in
safe condition. This instruction documentation contains information and warnings which
must be followed by the user
to
ensure safe operation and
to
maintain the product in a safe
condition.
SAFETY EARTH GROUND
A
uninterruptible safety earth ground must be provided from the main power source
or
product input wiring terminals, power cord,
SAFETY
A
Indicates instrument damage can occur
A
Indicates hazardous voltages.
&
-
Indicates earth (ground) terminal
WARNING
SYMBOLS
A
WARNING
~~~~ ~
note denotes a hazard. It calls attention to a procedure,
practice, or the like, which,
could result in personal injury.
if
supplied power cord set.
indicated operating limits are exceeded.
~ ~
if
not correctly performed or adhered to,
Do
not proceed beyond a
WARNING
sign until the indicated conditions are fully understood and met.
~
A
CAUTION
CAUTION note denotes a hazard. It calls attention
procedure, practice,
to,
could result in damage
or
the like, which, if not correctly performed
to
or
destruction
of
part
to
an operation
or
all of the product.
not proceed beyond an CAUTION note until the indicated conditions are hlly
understood and met.
1010,
or
adhered
to
Do
a
the
2
Chapter
1
Safety Considerations for this Instrument
Regulatory
Information
(Updated
March
1999)
WARNING
This product is a Safety Class I instrument (provided with
a
protective earthing ground incorporated in the power cord). The
mains plug shall only be inserted in
a
socket outlet provided with a
protective earth contact. Any interruption of the protective
conductor inside or outside of the product is likely
product dangerous. Intentional interruption
Whenever it
is
likely that the protection has been impaired, the
is
to
make the
prohibited.
instrument must be made inoperative and be secured against any
unintended operation.
If
this instrument
voltage reduction), make sure the common terminal
is
to be energized
via
an auto transformer (for
is
connected
the earth terminal of the power source.
If
this product
is
not used as specified, the protection provided by
the equipment could be impaired. This product must be used in
normal condition (in which
No
operator serviceable parts in this product. Refer servicing to
all
means for protection are intact) only.
qualified personnel. To prevent electrical shock, do not remove
covers.
Servicing instructions are for use by qualified personnel only. To
avoid electrical
qualified to do
shock,
so.
do not perform any servicing unless you are
to
a
The opening
dangerous voltages. Disconnect the product from
while it
The power cord
live for
5
of
covers
is
being opened.
is
or
removal of parts
connected to internal capacitors that
seconds after disconnecting the plug
is
likely to expose
all
voltage sources
from
its
my
remain
power supply.
For Continued protection against fire hazard, replace the line fuse(s)
only with
example, normal blow
250
V
fuse(s) or the same current rating and type (for
or
time delay). Do not use repaired fuses or
short circuited fuseholders.
Always use the three-prong ac power cord supplied with this
product. Failure
to
ensure adequate earth grounding by not using
this cord may cause product damage.
This product
Pollution Degree
INDOOR
is
USE
designed for use in Installation Category
2
per
IEC
1010
and
IEC
664
respectively. FOR
ONLY.
I1
and
This product has autoranging line voltage input, be sure the supply
voltage is within the specified range.
~~~~
Chapter
1
3
Regulatory Information (Updated
To
prevent electrical shock, disconnect instrument from mains (line)
before cleaning. Use a dry cloth or one slightly dampened with water
to clean the external case parts.
Ventilation Requirements: When installing the product in a cabinet,
the convection into and out of the product must not be restricted.
The ambient temperature (outside the cabinet) must be less than the
maximum operating temperature of the product by
watts dissipated in the cabinet.
cabinet
is
used.
March
1999)
greater than
Do
not attempt to clean internally.
4"
C
for every
If
the total power dissipated in the
800
watts, then forced convection must be
100
Product
Markings
CE - the CE mark
accompanied by
CSA
-
the
CSA
a
mark
is
a registered trademark
of
the European Community. A CE mark
year indicated the year the design was proven.
is
a registered trademark
of
the Canadian Standards Association.
4
Chapter
1
CERTIFICATION
Hewlett-Packard Company certifies
from
the factom. Hewlett-Packard further certifies that its calibration measurements are traceable to the
United States National Bureau of Standards, to the extent allowed
that
this
product met
its
published specifications at
by
the
Bureau's calibration facility, and
the
time of shipment
to the calibration facilities of other International Standards Organization members.
WARRANTY
This Hewlett-Packard instrument product is warranted against defects
date
period of one year from
option, either repair
For
warranty senrice
shall prepay shipping charges to
However, Buyer shall pay all shipping charges, duties, and taxes for products returned
country.
HP warrants that its software and firmware designated by HP for use with an instrument will execute
its programming instructions when properly installed on that instrument. HP does not warrant that the
operation of the instrument,
The foregoing warranty shall not apply to defects resulting from improper
Buyer, Buyer-supplied software
environmental specifications
NO OTHER WARRANTY
IMPLIED WARRANTIES
or
or
of shipment. During the warranty period, Hewlett-Packard Company will at
replace products which prove
repair, this product must be returned
HP
and HP shall pay shipping charges to return the product
or
sohare,
or
firmware will be uninterrupted
LIMITATION
or
interfacing, unauthorized modification
for
the product,
IS
EXPRESSED OR IMPLIED. HP SPECIFICALLY DISCLAIMS THE
OF
MERCHANTABILITY AND FITNESS FOR A PAWICULAR PURPOSE.
or
to
be defective.
to
a service facility designated by HP. Buyer
OF
WARRANTY
improper site preparation
in
material and workmanship for a
to
the Buyer.
to
HP from another
or
error free.
or
inadequate maintenance by
or
misuse, operation outside of the
or
maintenance.
its
EXCLUSIVE REMEDIES
THE REMEDIES PROVIDED HEREIN ARE BUYERS SOLE AND EXCLUSIVE REMEDIES.
HP
SHALL NOT BE LIABLE FOR
CONSEQUENTIAL DAMAGES, WHETHER BASED ON CONTRACT, TOFU', OR
LEGAL THEORY.
ANY
DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR
ANY
OTHER
ASSISTANCE
Product maintenance agreements and other customer assistance agreements are available for HewlettPackard products.
For
any assistance, contact your nearest Hewlett-Packard Sales and Service Office. Addresses are provided
at the back
of
this manual.
Safety Considerations
Model
8903B
SAFETY
GENERAL
This product and related documentation must be reviewed for familiarization with safety markings and
instructions before operation.
This product
with a protective earth terminal).
BEFORE
Verify that the product is set to match the available
line voltage and the correct fuse
SAFETY EARTH GROUND
An uninterruptible safety earth ground must be provided from the main power source to the product input
wiring terminals, power cord,
set.
SAFETY SYMBOLS
/I\
is
necessary for the user to refer to the instruction
manual (refer to Table of Contents).
is
a Safety Class I instrument (provided
APPLYING
Instruction manual symbol: the product will
be marked with this symbol when
Indicates hazardous voltages.
POWER
or
is
installed.
supplied power cord
CONSIDERATIONS
it
(WARNING
Any interruption of the protective (grounding) conductor (inside
ment)
terminal will cause a potential shock hazard
that could result
ing one conductor of a two conductor outlet
is not sufficient protection).
been impaired, the instrument
inoperative and be secured against any unintended operation.
If this instrument is to be energized via an
autotransformer (for voltage reduction) make
sure the common terminal
earth terminal
Servicing instructions are
trained personnel only.
electric shock, do not perform any servicing
unless qualified to do
or
disconnecting the protective earth
Whenever it
is
likely that the protection has
of
or
in
personal injury. (Ground-
the power source.
so.
I
outside
is
for
To
the
must
be made
connected to the
use by service-
avoid dangerous
instru-
Indicates earth (ground) terminal.
The WARNING sign denotes a
hazard. It calls attention to a
procedure, practice,
performed
jury.
the indicated conditions are fully understood and met.
operating procedure, practice,
correctly performed
age to
not proceed beyond a CAUTION sign until the indicated conditions are fully understood and met.
or
Do
not proceed beyond a WARNING sign until
or
destruction of part
or
the like, which,
adhered to, could result in personal in-
The
CAUTION
ard. It calls attention to an
or
or
adhered to, could result in dam-
or
all of the product.
if
not correctly
sign denotes a haz-
the like, which, if not
Do
Adjustments described
formed with power supplied to the instrument
while protective covers are removed. Energy
available at manypoints may,
sult in personal injury.
Capacitors inside the instrument may still be
charged even
connected from its source of supply.
For
continued protection against fire hazard,
replace the line fuse(s) only with
of the same current rating and type (for exam-
ple, normal blow, time delay, etc.).
rep a ired fuses
fuseholders.
if
the instrument
in
the manual are per-
if
contacted, re-
has
250V
Do
o
r
s
ho r t
c irc
been dis-
fuse(s)
not use
u
i
t ed
Model
8903B
Safety Considerations
ATTENTION
Static Sensitive
Devices
This instrument was constructed in an ESD (electro-static discharge) protected environment. This is because most of the semiconductor devices used
by static discharge.
Depending on the magnitude of the charge, device substrates can
be punctured
charge. The results can cause degradation of device performance,
early failure,
These charges are generated
tact, separation of materials, and normal motions of persons
working with static sensitive devices.
When handling
devices, adequate precautions must be taken to prevent device damage
or
Only those who are thoroughly familiar with industry accepted
techniques for handling static sensitive devices should attempt to
service circuitry with these devices.
In all instances, measures must be taken to prevent static charge
build-up on work surfaces and persons handling the devices.
For
further information on ESD precautions, refer to “SPECIAL
HANDLING CONSIDERATIONS
DEVICES,’
or
or
destruction.
in
Section VIII Service Section.
in
this
instrument are susceptible to damage
destroyed by contact
immediate destruction.
in
or
servicing equipment containing static sensitive
or
mere proximity of a static
numerous ways such
FOR
STATIC SENSITIVE
as
simple con-
HP 8903B
Table
of
Contents
TABLE
Section +General Information
Introduction
Specifications
Safety Considerations
Instruments Covered By Manual
Manualchanges
Description
General
Audio Testing
Transceiver Testing
Systems
Options
Electrical Options
Mechanical Options
Hewlett-Packard Interface Bus
Compatibility
Selecting the HP-IB Address
Accessories Supplied
Electrical Equipment Available
HP-IB Controllers
Front-to-Rear-Panel Connectors Retrofit Kit
Rear-to-Front-Panel Connectors Retrofit Kit
Mechanical Equipment Available
Chassis Slide Mount Kit
Chassis Tilt Slide Mount Kit
Recommended Test Equipment
Principles
Voltmeter and Notch Filter
Counter
Source
Controller
Basics
of
ACLevel
Frequency
DCLevel
Signal Impurities
Distortion
SINAD
Signal-to-Noise Ratio
Internal Source
Plotting
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...........................................
of
Operation
for
Simplified Block Diagram
..........................................
.....................................................
.....................................................
....................................................
Audio Measurements
..........................................
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...................................................
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.................................................
.....................................................
OF
CONTENTS
.................................
.................................
..............................
1.1
1-1
1.2
1.2
1-2
1-3
1-3
1-3
1-4
1-5
1-6
1-6
1-6
1-8
1-8
1-8
1-8
1-8
1-8
1-8
1-8
1-9
1-9
1-9
1-9
1-9
1-10
1-11
1-11
1-12
1-12
1-12
1-13
1-13
1-13
1-13
1-15
1-15
1-16
1-16
Table
of
Contents
Section 2-Installation
HP
8903B
Introduction
Initial Inspection
Preparation
Power Requirements
Line Voltage and Fuse Selection
Power Cables
HP-IB Address Selection
Interconnections
Mating Connectors
Operating Environment
Bench Operation
Rack Mounting
Storage and Shipment
Environment
Packaging
.....................................................
...................................................
for
Use
.................................................
...............................................
........................................
...................................................
............................................
.................................................
...............................................
...............................................
.................................................
..................................................
................................................
...................................................
.....................................................
Section %Operation
Introduction
General
Operating Characteristics
"urn-On Procedure
Local Operation
Remote Operation
Operator's Checks
Operator's Maintenance
Front-Panel Features
Basic Functional Checks
Simplified Operation
Rear-Panel Features
Description
Equipment
Procedure
Preliminary Check
AC Level and Output Level Check
Filter Check
Distortion Check
SINAD Check
Signal-to-Noise Ratio Check
Sweep, X Axis, Y Axis, Pen Lift, and DC Level Check
HP-IB Functional Checks
Description
Initial Setup
Equipment
Address Recognition
Remote and Local Messages and the LCL Key
Sending the Data Message
Receiving the Data Message
Local Lockout and Clear Lockout/Set Local Messages
....................................................
......................................................
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2.1
2.1
2.1
2.1
2-2
2.2
2.3
2.5
2.5
2.6
2.6
2.6
2.8
2.8
2.8
-3-1
3-1
3-1
3-1
3-2
3-3
3-3
3-4
3-6
3-12
3-8
3-11
3-12
3-12
3-12
3-12
3-12
3-13
3-15
3-15
3-15
3-15
3-16
3-16
3-16
3-16
3-16
3-17
3-17
3-18
3-18
HP 8903B
Table
of
Contents
ClearMessage
AbortMessage
Status Byte Message
Require Service Message
Trigger Message and Clear Key Triggering
Remote Operation. Hewlett-Packard Interface Bus
HP-IB Compatibility
Remote Mode
LocalMode
Addressing
Data Messages
Receiving the Data Message
Sending the Data Message
Receiving the Clear Message
Receiving the Trigger Message
Receiving the
Receiving the Local Message
Receiving the Local Lockout Message
Receiving the Clear Lockout/Set Local Message
Receiving the Pass Control Message
Sending the Require Service Message
Selecting the Service Request Condition
Sending the Status Byte Message
Sending the Status Bit Message
Receiving the Abort Message
HP-IB
ACLevel
Amplitude
Automatic Operation
CommonMode
DCLevel
Default Conditions and Power-up Sequence
Detector Selection
Display Level in Watts
Display Source Settings
Distortion
Distortion Level
Error Disable
Error Message Summary
Filters
Float
Frequency
Hold Decimal Point
Hold Settings
HP-IB Address 3-79
Increment
Input Level Range (DC Level)
Input Level Range (Except DC Level)
Monitor
Notch~ne
Output Impedance
Plot Limit 3-96
Post-Notch Detector Filtering (Except SINAD)
Syntax
......................................................
.......................................................
......................................................
......................................................
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.........................................................
......................................................
......................................................
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..................................
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.............................................
.................................................
...................................................
...................................................
.................................................
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..........................................
.........................................
........................................
Remote
Message
........................................
.........................................
....................................
..............................
.....................................
....................................
...................................
......................................
.......................................
.........................................
and Characteristics Summary
..................................
................................................
...................................................
...................................
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...................................................
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.................................
3-18
3-19
3-20
3-21
3-22
3-22
3-23
3-23
3-23
3-23
3-26
3-26
3-30
3-31
3-32
3-32
3-33
3-33
3-33
3-33
3-33
3-34
3-34
3-35
3-35
3-35
3-42
3-44
3-46
3-47
3-50
3-52
3-53
3-55
3-57
3-58
3-60
3-62
3-64
3-68
3-72
3-74
3-76
3-78
3-82
3-84
3-86
3-88
3-91
3-93
3-98
Table of Contents HP 8903B
Post-Notch Gain
Rapid Frequency Count
Rapidsource
RATIO and LOG/LIN
Read Display
Service Request Condition
Signal-to-Noise
Special Functions
Sweep
Sweep Resolution
Time Between Measurements
X-YRecording
.......................................................
.................................................
.............................................
...................................................
..............................................
to
HP-IB
.............................................
............................................
..................................................
.................................................
.................................................
..........................................
..................................................
Section 4-Performance
Introduction
Equipment Required
TestRecord
Calibration Cycle
Abbreviated Performance Testing
Performance Test
Performance Test
Performance Test 3 Distortion and Noise
Performance Test 4 Distortion, SINAD, and Signal-to-Noise Accuracy
Performance Test 5 Frequency Accuracy and Sensitivity
Performance Test 6 Audio Filters
Performance Test
Performance Test
.....................................................
.................................................
......................................................
...................................................
..........................................
1
AC
Level Accuracy and Output Level Accuracy and Flatness
2
DC Level Accuracy
.....................................
....................................
............................
.........................................
7
Input and Output Impedance
8
Common-Mode Rejection Ratio
................................
..............................
...............
....................
3-100
3-102
3-105
3-109
3-112
3-114
3-116
3-121
3-128
3-131
3-134
3-135
4.1
4.1
4-1
4.1
4.1
4-2
4-12
4-14
4-16
4-19
4-21
4-28
4-29
Section 5-Adjustments
Introduction
Safety Considerations
Equipment Required
Factory-Selected Components
Post-Repair Tests, Adjustments, and Checks
Related Adjustments
Adjustment
Adjustment
Adjustment 3 Common Mode Rejection
Adjustment 4 Input DC
Adjustment 5 400 Hz High-Pass and Weighting Bandpass Filters
Adjustment 6 Notch Filter Tune and Balance
Adjustment
Adjustment
Adjustment 9 Oscillator and Output Attenuator
.....................................................
................................................
.................................................
............................................
....................................
.................................................
1
Internal Reference Frequency
2
Input Flatness
............................................
....................................
......................................
Offset
...........................................
..................................
7
Voltmeter
8
SINAD Meter
..............................................
............................................
.................................
.......................
5.1
5.1
5.1
5.1
5.2
5.2
5.4
5.5
5.8
5.9
5-10
5-12
5-13
5-15
5-16
Model
8903B
General Information
1-1.
INTRODUCTION
This manual contains information required to install, operate, test, adjust, and service the HewlettPackard Model 8903B Audio Analyzer. This manual documents options installed in the Audio Analyzer
such
This section of the manual describes the instruments documented by the manual and covers
instrument description, options, accessories, specifications, and other basic information. This section
also contains principles of operation on a simplified block diagram level and basic information on audio
measurements. The other sections contain the following information:
Section
address selection for remote operation), and storage and shipment.
Section
operating instructions for both local and remote operation, and maintenance information.
Section
instrument against the critical specifications in Table
Section
1
GENERAL INFORMATION
as
rear-panel connections and internal plug-in filters.
2,
Installation:
3,
Operation:
4,
Performance Tests:
provides information about initial inspection, preparation for use (including
provides information about panel features, and includes operating checks,
provides the information required
1-1.
to
check performance of the
Section
Section
Section
Section
Sections 1 through 5 are bound in this volume, the Operation and Calibration Manual. One copy of the
Operation and Calibration Manual is supplied with the instrument. Sections 6 through
in
two
instrument unless specifically requested (as Option 915) at time of instrument order. Copies of all
volumes can be ordered separately through your nearest Hewlett-Packard office. The part numbers are
listed on the title page of this manual.
Also listed on the title page of this manual, below the manual part number, is a microfiche part number.
This number may be used to order 100
Each microfiche contains up to 96 photo-duplicates of the manual’s pages. The microfiche package also
includes the latest MANUAL UPDATES packet, as well as all pertinent Service Notes.
1-2.
SPECIFICATIONS
Instrument specifications are listed in Table
which the instrument may be tested. Characteristics listed under Supplemental Information, Table
are not warranted specifications but are typical characteristics included as additional information for
the user.
5,
Adjustments:
6,
Replaceable Parts:
7,
Instrument Changes:
8,
Service:
separate volumes, the Service Manual. Copies of the Service Manual are not supplied with the
provides the information required to properly adjust the instrument.
provides ordering information for all replaceable parts and assemblies.
provides instrument modification recommendations and procedures.
provides the information required
x
150
mm
1-1.
These are the performance standards, or limits against
to
repair the instrument.
(4
x
6 inch) microfilm transparencies of this manual.
8
are bound
1-2,
1-1
General Information Model
1-3.
SAFETY CONSIDERATIONS
8903B
This product is a Safety
Audio Analyzer and all related documentation must be reviewed for familiarization with safety markings
and instructions before operation. Refer to the Safety Considerations page found at the beginning of
this manual
(installation, performance testing, adjustment,
1-4.
INSTRUMENTS COVERED
Serial
stamped on the serial number plate attached to the rear
letter constitute the serial number prefix, and the last five digits form the suffix. The prefix is the same
for all identical instruments.
however,
apply directly to instruments having the same serial prefix(es) as listed under SERIAL NUMBERS
on the title page.
Options.
documented in this manual. The differences are noted under the appropriate paragraph such
in Section
1-5.
MANUAL UPDATES
An instrument manufactured after the printing of this manual
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I instrument (that is, provided with a protective earth terminal). The
for
a summary of the safety information. Safety information pertinent to the task at hand
or
service) is found throughout the manual.
BY
MANUAL
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is
assigned sequentially and is different for each instrument. The contents of this manual
Electrical Option
1,
This instrument has a two-part serial number in the form
of
the instrument. The first four digits and the
It
changes only when a change
001,
internal plug-in filter options, and various mechanical options are
the Replaceable Parts List, and the schematic diagrams.
is
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or
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is
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1-2
Model 8903B
1-6.
DESCRIPTION
General
The HP Model 8903B Audio Analyzer is a complete audio measurement system covering the frequency
range of
source has a maximum open-circuit output of 6 Vrms and a selectable output impedance of either
6000. The analyzer can perform distortion analysis, frequency count, and ac level, dc level, SINAD, and
signal-to-noise ratio measurements. The Audio Analyzer reduces the number of instruments required
in many applications involving audio signal characterization.
20
Hz
to
100 kHz.
General Information
It
combines a low-distortion signal source with a signal analyzer. The
50
or
The Audio Analyzer is easy
distortion measurements, the Audio Analyzer automatically tunes to and levels the input signal.
Measurement and output ranges are automatically selected for maximum resolution and accuracy.
firthermore, tuning is independent of the source. Thus, the source can be set to one frequency while
is
the analyzer
tune the analyzer
The combined capabilities of the instrument are enhanced by microprocessor control, resulting
capability than would be available from separate instruments. For example, when making signal-to-noise
ratio measurements, the Audio Analyzer monitors the ac level while turning the source on and
microprocessor then computes and displays the ratio of the on and
in either
In addition, the source can be swept. This makes measurements such as frequency response
distortion characterization simple
parameters and versatile display formats. For example, ac level can be displayed in V, mV, dBm into
6000, watts,
Virtually all functions are remotely programmable through the Hewlett-Packard Interface Bus
(HP-IB'). Programming is easy
input. This eliminates the need to switch between multiple inputs under remote control and reduces
software development time and hardware costs. The Audio Analyzer measures the true rms level
on all ac measurements. True rms measurements assure greater accuracy when measuring complex
waveforms and noise. For those applications where average detection
be switched to average-responding
distortion measurements typically can be made to less than
20
kHz
at
(Serial Prefix 2730A and above) can be switched
This detector is designed
measuring the distortion on a signal
to
the source).
5%
or
dB.
or
as a ratio (in
a 1.5V level. For those applications where quasi-peak detection
to
use. All measurements are selected by one
at
another frequency (that is, there
off
levels. The ratio can be displayed
to
perform. Microprocessor control allows flexible entry of source
%
or
dB)
referenced to an entered
and
straightforward; all measurements are made through a single
(rms
calibrated) detection through special functions. Accurate
to
this type of detection through special functions.
to
meet the requirements specified by CCIR 468-3.
or
measured value.
0.003%
or
two keystrokes. For
is
no need to
or
complete
is
required, the analyzer can
(-90
dB)
between
is
required, the analyzer
20
in
more
off.
The
Hz and
Audio Testing
The Audio Analyzer has numerous features which make audio testing simple and convenient.
These features include flexible data entry and display formats, convenient source control, and swept
For
measurements capability.
measurements can be displayed in volts, dBm into 600R,
%
or
dB
in
is simplified by using the source frequency increment and decrement keys together with the relative
display feature.
When sweeping, the Audio Analyzer tuning steps
an x-y recorder, hard copy measurement results can be obtained. X-axis scaling
entered start and stop frequencies. Y-axis scaling
the plot limits entered through the keyboard. Any valid display units (except mV) are allowed when
plotting. To change the scaling from frequency response to swept distortion plots, simply key in new
HP-IB: Not just IEEE-488, but the hardware, documentation and support that delivers the shortest path to a
measurement system.
relative to a measured
A
major contribution of the Audio Analyzer is its ability to make swept measurements.
example, distortion results can be displayed in
or
watts. Measurement results can be displayed
or
entered value. Finding the
its
source frequency in logarithmic increments. With
is
determined by the measurement units selected and
3
dB
points of filters and amplifiers
%
or
dB.
AC level
is
determined by the
1-3
General Information Model
8903B
values for the plot limits.
No
adjustment of the x-y recorder
is
necessary. The Audio Analyzer also
features high accuracy. The instrument can typically measure flatness
of
20
Hz to
20
and
1-2.
kHz and swept distortion over the same range to
Figure
9
w
v,
p
'0
g
'?o
-
I-
+0.2,
1-1.
npical Combined Source and
-70
-75
-80
-80
-85
I,,
0.003%
AC
!
9
-95
D
2
-100
3
0
-105
v)
-110
20Hz
5OHz
2OOHz
500Hz
FREQUENCY
PkHr
5kHz
to
0.5%
(0.05
(-90
dB).
I1
Level Flatness
20kHz
dE3)
over the range
See Figures
1-1
Balanced
Figure
Input.
1-2.
Typical Combined Source and Analyzer Residual Distortion
(80
kHz
With Vsource Set to 1.5V
BW)
The Audio Analyzer has a selectable balanced input configuration for testing balanced
devices. For example, in the quest for higher output power, many audio amplifiers use bridged output
stages. Such amplifiers can be difficult to characterize because their outputs cannot be grounded. To
to
test these devices, the usual approach has been
use a balanced, calibrated isolation transformer
connected to an analyzer with an unbalanced input. Balanced inputs on the Audio Analyzer make
transformers unnecessary. With the analyzer input in the float position, connect the bridged device
directly to the Audio Analyzer to make measurements.
Transceiver Testing
The Audio Analyzer has several measurements and features specifically designed for transceiver testing.
It
has SINAD and signal-to-noise ratio measurements for receiver testing, optional internal plug-in
weighting filters for testing to international standards, a reciprocal counter for measuring squelch tones,
400
and an optional internal plug-in
Hz high-pass
transmitter audio distortion.
SINAD is one
sensitivity
of
the most basic receiver measurements. It must be made repeatedly when performing
or
adjacent-channel sensitivity tests. In the Audio Analyzer, the SIN AD measurement is
more heavily filtered than the distortion measurement in order to smooth the noisy signals encountered
in receiver testing. The filtering is optimized for excellent repeatability and speed
typical). Some automatic distortion analyzers have
SINAD on noisy signals. The Audio Analyzer overcomes this problem by tuning the notch filter to
filter
for eliminating squelch tones when measuring
(2
readings/second
a
tendency to become untuned when measuring
1-4
Model
8903B
the source frequency when measuring SINAD. SINAD measurement results are indicated both by the
digital display and a front-panel analog meter. The meter is specifically marked for
25
dB,
sensitivity and selectivity. For SINAD ratios less than
0.5
dB
rounded to the nearest
Signal-to-noise ratio measurements are also filtered for improved repeatability and speed
ing/second typical), and automatic display rounding
Audio Analyzer uses true
instruments employ average detection which reads low for noise. The discrepancy can be
greater and varies with the ratio being measured. For correlating results with past test data, the Audio
Analyzer’s detector can be switched via special functions
For those applications where quasi-peak detection is required, the analyzer (Serial Prefix
above) can be switched
to
meet the requirements specified by CCIR
For transceivers, the Audio Analyzer has an optional, internal plug-in seven-pole 400 Hz high-pass filter
for rejecting squelch tones. Rejection of squelch tones up to
audio distortion measurements
squelch tones.
Under remote control, the Audio Analyzer can generate
is
maximum count rate
applications such as unsquelching pagers (see Figure
8
to reduce digit flicker.
is
provided. For accurate noise measurements, the
rms
detection for both SINAD and signal-to-noise measurements. Most older
to
to
this type of detection through special functions. This detector is designed
468-3.
to
1%
residual distortion can be made without disabling the transmitter
or
ms/reading and the minimum tone duration
1-3).
the digital display
an average responding configuration.
250
Hz
is
greater than
count burst tone sequences. Typically the
is
12
General Information
EIA
is
40
dB.
ms. This
is
fast
and CEPT
automatically
1.5
2730A
Therefore,
enough for
(1
read-
dB
and
or
Figure
1-3.
Two-Tone
Burst
Sequence
(15
ms
Duration)
Systems
The Audio Analyzer features capabilities for general systems applications. The audio source
programmable in frequency, level, and output impedance has very low distortion. The distortion
measurements are fully automatic, programmable, and
is
1.5
first distortion measurement
The combined distortion of the internal source together with the measurement section is typically
0.003%
Often systems applications involve measuring low level ac signals. The Audio Analyzer features a full
range ac level display of
and from
Quasi-peak detection. The
Since many systems have noise problems, the Audio Analyzer has both
reject high frequency noise. In addition, the optional internal plug-in
line-related hum and noise by more than
Two special binary programming modes are available in remote operation. A rapid frequency count
mode provides a packed, four-byte output for fast counting. Also, a rapid source binary programming
mode
of data.
(-90
dB)
between
20
Hz
to
20
is
available which allows the internal oscillator tuning to be programmed directly with five bytes
20
0.3000
kHz). The ac detector is switchable between true rms, average-responding, and
3
seconds with a measurement rate of 2 readings/second thereafter.
Hz
and
20
kHz at a
mV with an accuracy of
dB
measurement bandwidth for each detector is greater than
68
dB.
1.5V
fast.
The typical time
level.
4%
of reading
to
(2%
of reading for levels
30
and
80
kHz low-pass filters
400
Hz
high-pass filter attenuates
tune and return the
500
>50
kHz.
is
mV
to
1-5
General Information
1-7.
OPTIONS
Electrical Options
Model 8903B
Electrical Option
001.
This option provides rear-panel (instead of front-panel) connections for both
the INPUT and OUTPUT HIGH and LOW BNC connectors.
Internal Plug-in Filter Options.
The Audio Analyzer has
two
plug-in filter positions; each position
can be loaded with any one of six optional filters. Each filter is referenced to its corresponding filter
position by one
as Option 010 which corresponds to the left-most filter position,
of
two
option numbers. For example, the 400 Hz high-pass filter option can be ordered
or
as
Option
050
which corresponds
to the right-most filter position. These optional plug-in filters can be configured in any combination
desired.
there is no filter ordered for a position, a jumper
is
loaded and a label marked
(If
is placed above the filter key on the front panel.) The following list includes the name and option
numbers for each available filter.
0
400 Hz High-Pass Filter (Option 010,050)
0
CCITT Weighting Filter (Option 011, 051)
0
CCIR Weighting Filter (Option 012, 052)
0
C-MESSAGE Weighting Filter (Option 013, 053)
0
CCIR/ARM Weighting Filter (Option 014,
0
“A”
Weighting Filter (Option 015,
055)
054)
Specific information on each plug-in filter option can be found in the Detailed Operating Instructions
in Section 3 under “Filters”.
Mechanical Options
The following options may have been ordered and received with the Audio Analyzer.
ordered with the original shipment and are now desired, they can be ordered from the nearest HewlettPackard office using the part number included in each of the following paragraphs. The mechanical
options are shown in Figure 1-4.
If
they were not
“No
Filter”
Front Handle Kit (Option
HP
part number 5061-9689.
Rack Flange
Kit
(Option
907).
908).
Ease of handling
is
increased with the front-panel handles. Order
The Audio Analyzer can be solidly mounted to an instrument rack
using the flange kit. Order HP part number 5061-9677.
Rack Flange and Front Handle Combination Kit (Option 909).
a
a rack flange kit packaged together; it is composed of
HP
Order
part number 5061-9683.
unique part which combines both functions.
This
is
not a front handle kit and
1-6
Model
8903B
General Information
SPARE INTERNAL FUSES
OPTION
909
RACK FLANGE AND FRONT
HANDLE COMBINATION KIT
BNC TO BANANA PLUG ADAPTERS
’
OPTION907
FRONT HANDLE KIT
Figure
1-4.
OPTION
908
RACK FLANGE KIT
NOTE:
Refer
to
ACCESSORIES
HP
8903B Accessories Supplied, and Options
SUPPLIED,
for
more
details.
907,
908, and 909
1-7
General Information Model 8903B
1-8.
HEWLETT-PACKARD INTERFACE BUS
Compatibility
The Audio Analyzer is compatible with HP-IB to the extent indicated by the following code: SH1,
T5,
AH1,
bus via open collector TTL circuitry. An explanation of the compatibility code can be found in IEEE
Standard 488,
ANSI Standard MC1.l.
Analyzer, refer to
TEO, L3, LEO,
IEEE Standard Digital Interface for Programmable Instrumentation
Remote Operation, Hewlett-Packard Interface
SR1,
RL1, PPO, DC1, DT1,
For
more detailed information relating to programmable control of the Audio
CO,
El.
The Audio Analyzer interfaces with the
or the identical
Bw
in Section 3 of this manual.
Selecting the HP-IB Address
The HP-IB address switches are located within the Audio Analyzer. The switches represent a fivebit binary number. This number represents the talk and listen address characters which an HP-IB
two
controller is capable of generating. In addition,
to talk only
HP-IB
1-9.
ACCESSORIES SUPPLIED
or
Address Selection
listen only. A table in Section 2 shows all HP-IB talk and listen addresses. Refer to
in Section 2
of
this manual.
more switches allow the Audio Analyzer to be set
The accessories supplied with the Audio Analyzer are shown in Figure
Fast
blow fuses with a 1.5A rating for 100/120 Vac operation (HP 2110-0043) and a
220/240 Vac operation (HP 2110-0001) are supplied. One fuse is installed in the instrument at the
time of shipment. The rating of the installed fuse is selected according to the line voltage specified by
1-1
the customer.
to the country of destination.
Four type BNC-to-banana-plug adapters (HP 1250-2164) are also supplied for use when double-ended
inputs
conductor of the BNC connector adapted to. These adapters are used when the front-panel INPUT
or
0.
ELECTRICAL EQUIPMENT AVAILABLE
(Also refer to Service Accessories, Table
HP-I6
The Audio Analyzer has
controller
or
OUTPUT FLOAT switches are set to FLOAT.
Controllers
If
the voltage
outputs are desired. The conductor of the banana connector is connected to the center
or
computer for automatic systems applications.
is
not specified, the rating of the installed fuse will be selected according
an
HP-IB interface and can be used with any HP-IB compatible computing
Front-to-Rear-Panel Connectors Retrofit Kit
This kit contains all the necessary components and full instructions for converting instruments with
front-panel connections for INPUT and OUTPUT HIGH and LOW to rear-panel connections.
serial prefixes 2730A and below, order
above, order HP part number 08903-60199. After installation and calibration, performance will be
identical to the
HP
8903B Option 001.
1-4.
1.OA
1-4.)
HP
part number 08903-60171. For serial prefix 2742A and
rating for
For
Rear-to-Front-Panel Connectors Retrofit Kit
This kit contains all the necessary components and full instructions for converting instruments with
rear-panel connections for INPUT and OUTPUT HIGH and
serial prefix 2730A and below order HP part number 08903-60172.
order HP part number 08903-60200. After installation and calibration, performance will be identical
to the standard HP 8903B.
1-8
LOW
to front-panel connections. For
For
serial prefix 2742A and above,
rev.26JU.9
Model
1-1
1.
8903B
MECHANICAL EQUIPMENT AVAILABLE
General Information
Chassis
This kit
components
part number
adapters for non-HP rack enclosures.
Chassis Tilt
This kit
instrument up
part
AC/OC
HIGH
IN^
c>-
I" I
%?
ACfOC
Slide
number
ATTFTOR
Mount Kit
is
extremely useful when the Audio Analyzer
or
the rear-panel
1494-0060
Slide
is
INPUT
-
Mount Kit
the same as the Chassis Slide Mount Kit above except
or
down
90".
1494-0061
OVER- TO-SINGLE- PROGRAMMABLE
VOLTAGE ENOEO- GAIN
PROTECTION
-
OVFII-
VOLTAGE
PROTECTION
for
OIFFERENTIAL-
AMPLICIER AMPLIFIER
VOLTAGETO-TIME
CONVERTER
is
possible without removing the instrument from the rack. Order HP
for
431.8
mm
(17
Order HP part number
the correct adapters for non-HP rack enclosures.
I
is
rack mounted. Access
in.) fixed slides and part number
it
also allows the tilting of the
INTERNAL
PLUG-IN
HP/BP
I
1494-0062
1I
FILTER
for
431.8
mm
PROGRAMMABLE PROGRAMMABLE
to
internal circuits and
1494-0061
(17
for the correct
in.) tilting slides and
!t
MONITOR
1-12.
1-13.
SINAO METER
-0
RB8giE;o
2
rn
KEYBOARO AN0 OISPLAY
a8
ooDD
..--
D
w..
0
-P
Figure
1-5.
Simplified
HP
8903B
Audio Analyzer
Block
Diagram
RECOMMENDED TEST EQUIPMENT
Table
1-3
lists the test equipment recommended for use in testing, adjusting, and servicing the Audio
If
Analyzer.
any of the recommended equipment
specifications may be substituted. Table
1-3
is
unavailable, instruments with equivalent minimum
also includes some alternate equipment listings.
PRINCIPLES OF OPERATION FOR SIMPLIFIED BLOCK DIAGRAM
The HP
a general purpose voltmeter with
Measurements are managed by a microprocessor-based Controller. This combination forms an
instrument that can make most common measurements on audio circuits automatically. To add to its
versatility, the Audio Analyzer also has selectable input filters, logarithmic frequency sweep,
outputs
The operation
Counter, Source, and Controller. Refer to Figure
8903B
for
Audio Analyzer combines three instruments into one: a low-distortion audio source,
a
tunable notch filter at the input, and a frequency counter.
plotting measurement results vs. frequency, and HP-IB programmability.
of
the instrument
is
described in the following order: Voltmeter and Notch Filter,
1-5.
x
and
y
1-9
General Information Model
8903B
Voltmeter
The amplitude measurement path flows from the INPUT connectors (HIGH and LOW) to the MONITOR output (on the rear panel) and includes the Input RM$/Average and Output RMS/Average/QuasiPeak Detectors, dc voltmeter (the Voltage-to-Time Converter and Counter), and SINAD meter circuitry.
Measurements are made on the difference between the signals at the HIGH INPUT connector and the
LOW INPUT connector
Signals that are common to both the HIGH and LOW connectors are balanced out.
The input signal
Input Attenuator to
Protection circuit opens whenever its input exceeds 15V. The differential signal
single-ended signal (that is, a signal referenced to ground) and amplified. In the dc level mode, the dc
voltage
Gain Amplifier which
Amplifier are programmed to keep the signal level into the Input Detector and Notch Filter between
1.7
modes.
The output from the first Programmable Gain Amplifier is converted to dc by the Ranging RMS
Detector and measured by the dc voltmeter. The output of this detector is used to set the gain of
the input circuits. The signal then passes through the
Detector and becomes the numerator of the SINAD measurement and the denominator of the distortion
measurement (refer to
to make the ac level measurement; the Output RMS/Average/Quasi-peak Detector is used for this
measurement. For dc level measurements, the Ranging RMS Detector also monitors the ac component
(if there
otherwise, the gain of the input path is determined by measuring the dc level.
two internal plug-in filters can be inserted into the signal path. The
used to suppress line hum
weighting filters have bandpass frequency responses that simulate the “average” response of human
hearing. In the SINAD, distortion, and distortion level modes, the frequency of the input signal is
counted at the output of the internal plug-in HP/BP Filters.
When measuring SINAD, distortion,
the Notch Filter. The output from the filter
and signal-to-noise ratio modes the Notch Filter
the output from the Notch Filter is converted to dc by the Output RMS/Average/Quasi-peak Detector
and measured by the dc voltmeter.
When measuring distortion
counted at the input to the filter. Coarse tuning
circuitry internal to the Notch Filter. When measuring SINAD, the Notch Filter
the Controller to the same frequency as the internal source. Thus, a SINAD measurement
only made with the internal source as the stimulus and permits measurements in the presence
large amounts of noise (where the Controller would be unable to determine the input frequency).
external source
of
Filter, amplify the low-level noise and distortion signals from the Notch Filter. The overall gain of the
two amplifiers is normally set to maintain a signal level of
The 30 kHz and
the
often used to remove the high-frequency noise components in low-frequency SINAD and distortion
measurements. The output from the second Programmable Gain Amplifier drives the rear-panel
MONITOR output connector. The frequency of this signal
ac
The Output Detector is read by the dc voltmeter in the ac level, SINAD (the denominator), distortion
(the numerator), distortion level, and signal-to-noise ratio measurement modes.
and
Notch
is
measured at this point by the dc voltmeter. The signal
and 3 Vrms
is
one) and lowers the gain of the input path
the frequency of the internal source. The
3
dB
bandwidth of the measurement system is approximately
level
and signal-to-noise ratio measurement modes because of the increased sensitivity at this point.
Filter
(or
ground). Differential and common-mode levels can be as high as 300V.
is
ac coupled for all measurement modes except dc level. The signal
a
level of 3V
is
ac coupled. The gain
to
optimize their effectiveness and accuracy, particularly in the distortion and SINAD
Basics
or
less. To protect the active circuits that follow, the Over-Voltage
of
this amplifier and the Differential-to-Single-Ended
of
Audio Measurements).
is
further amplified by a Programmable
HP/BP
The Input RMS/Average Detector
if
the signal will overload the input amplifiers;
filters to the Input RMS/Average
At
400
Hz high-pass filter
or
the low frequency squelch tone used on some mobile transceivers. The
or
distortion level, the fundamental of the signal is removed by
is
the distortion and noise of the signal. In the ac level
is
bypassed. After amplifying and low-pass filtering,
or
distortion level, the Notch Filter
is
via the Controller. Fine tuning and balance are via
is
used in the SINAD measurement mode, the source frequency must be within
two
Programmable Gain Amplifiers, following the Notch
80
kHz LP Filters are selected from the Keyboard. With no low-pass filtering,
is
automatically tuned to the frequency
0.3
to 3V at the MONITOR output.
750
kHz. The filters are most
is
also measured by the Counter in the
It
is
scaled by the
is
converted
this point, one of the
is
coarse tuned by
is
is also used to set the
is
not used
is
usually
normally
If
to
5%
a
of
an
1-10
Model
8903B
gain
of
the
two
Programmable Gain Amplifiers. Both the input and output detectors can be configured
via special functions to respond to the absolute average of the signal instead
In the SIN AD mode the outputs from the Input RMS/Average and Output RMS/Average/Quasi-peak
of
Detectors are converted to a current representing the log of the ratio
to
Meter Amplifier
very noisy conditions, the panel meter makes
The Voltage-to-Time Converter converts the dc inputs into a time interval which
Counter. The Output Detector can also be configured via special functions to respond
of the signal. This type of detector
types. The Quasi-peak Detector has a fast rise time coupled with a slow decay time constant which
“captures” impulses
drive the SINAD panel meter. Since SINAD measurements are often made under
it
or
other
signals
easier
is
designed
with a high crest factor (noise
to
to
average the reading and to discern trends.
respond to impulse type signals better than other
the
or
repetitive signal bursts).
General Information
of
the true
two
signals by the SINAD
is
measured by the
to
the quasi-peak
Counter
rms
value.
The Counter
of the signal at
The reference
Counter has four inputs and three modes of operation:
Voltage Measurement.
accumulated count is proportional
and distortion level), the count
display. For ratio measurements (SIN
measurements are processed and displayed. For SINAD and distortion, the ratio of the output of the
Input RMS/Average Detector and Output RMSIAveragejQuasi-Peak Detector
to-noise, the ratio of
computed. One output is with the Oscillator on, the other is with the Oscillator
Input Frequency Measurement.
Filters is conditioned by the Counter Input Schmitt Trigger to make it compatible with the Counter’s
input. The period of the signal is then counted, the count
frequency is displayed on the left display.
Source Frequency Measurement.
when the Oscillator
of the source frequency, the output
the result processed by the Controller.
is
a reciprocal counter. To measure frequency, it counts the period of one
its
input, then the Controller divides the number of periods by the accumulated count.
for
the Counter is the 2 MHz Time Base which also is the clock for the Controller. The
The time interval from the Voltage-to-Time Converter
to
the dc voltage.
is
processed directly by the Controller and displayed on the right
AD,
distortion, and signal-to-noise), the counts
two
consecutive outputs from the Output RMS/Average/Quasi-peak Detector is
The signal from the last Programmable Gain Amplifier or the HP/BP
The Counter measures the frequency
is
being tuned. The frequency is normally not displayed. To make a measurement
of
the Oscillator is fed
For
direct measurements (ac level, dc level,
is
computed. For signal-
off.
is
processed by the Controller, and the
of
the internal source only
into
the Counter, the period measured,
or
more cycles
is
counted. The
of
two
successive
and
Source
The source covers the frequency range from
from Keyboard by the Controller using a tune-and-count routine. (Note that the frequency is not
obtained by frequency synthesis.) The switch following the Oscillator is normally closed except in the
signal-to-noise ratio measurement mode
is
The output from the Oscillator
The Output Amplifier sets the source output level in fine steps. The Floating Output Amplifier converts
the single-ended input into a floating signal (either output can be grounded
The Output Attenuator sets the output level in coarse steps. The maximum signal to the OUTPUT
connectors is 6V into an open circuit
the source is
level.)
HP-IB
programmable to either
approximately
or
20
Hz
to
100
kHz.
It is tuned to the frequency entered
or
when an amplitude of OV
3V.
3V into the matching termination. The output impedance of
50
or
600R. (The keyboard-selected level
is
entered from the Keyboard.
or
floated up to
is
the open-circuit
1OV
peak).
1-11
General Information Model
Controller
The entire operation of the instrument is under control of a microprocessor-based Controller. The
Controller sets up the instrument at turn-on, interprets Keyboard entries, executes changes
of operation, continually monitors instrument operation, sends measurement results and errors to the
is
used
front-panel displays, and interfaces with HP-IB. In addition, its computing capability
For
circuit operation.
into ratios (in
’3%
example, it forms the last stage of the Counter, converts measurement results
or
dB),
etc. It also contains routines useful for servicing the instrument.
to
8903B
in
mode
simplify
1-14.
AC
BASICS
The “audion frequency range is usually taken to be from
that good, but the term is a convenient one to describe sub-RF frequencies encountered in electronics.
The frequency range of the Audio Analyzer extends beyond the audio range
up
Electronic instrumentation provides most of the tools for quantitative analysis of audio signals. Thus,
if
signal by a transducer of some kind (for example, strain gauge or microphone) before
Apart
in the audio range
frequency (pitch), and shape (timbre). You can also determine
are stable, and you can even make some quantitative measurements on it (for example, peak level, dc
offset, period, risetime, etc.). Many times, however, the parameter sought does not lend itself
visual analysis. Thus, the Audio Analyzer was designed.
general and specialized instruments, under microprocessor control, that make it easy for you to obtain
accurate, quantitative measurements on audio signals of any general waveshape.
OF
AUDIO MEASUREMENTS
to
100
kHz.
the signal is non-electrical (for example, mechanical
from attentive listening
is
visually with an oscilloscope. Here you get a feeling for the signal’s size (loudness),
to
a hi-fi system, the most intuitive way of analyzing an electrical signal
20
Hz to
or
acoustic),
It
combines into one instrument a series of
20
kHz. Few people have hearing
to
include fundamentals
it
must be converted
it
can be analyzed.
if
these parameters change with time
to
an electrical
to
Level
Consider the very common measurement of a signal’s ac rms level. To make this measurement with
an oscilloscope, you must first decide the nature of the signal, because from it, the relationship of the
rms
peak level to the
the rms value
This measurement is greatly simplified with a rms voltmeter which electronically measures the rms
level and displays the result. However, no other information about the signal is provided. The Audio
Analyzer contains both an rms- and an average-responding voltmeter. The
displayed whenever the AC
SPCL. The quasi-peak level can be displayed by entering
which converts the measurement result into watts for
is
level can be mathematically determined. If the signal is sinusoidal, for example,
the peak amplitude divided by
LEVEL
mode is selected. The average level can be displayed by entering
a.
rms
level of the signal
5.7
SPCL. A special function
a
specified (external) load resistance.
is
also provided
or
easy
is
5.2
1-12
Another important ac signal characteristic
you can easily set a reference level (such as
the change in level as the input frequency is changed. (The source’s level
too
must be checked.) The Audio Analyzer makes this measurement easier in three ways. First, the
it
analyzer contains a flat, wide-range oscillator that can be used as the stimulus. Second, the reference
100%
or
0
dB
can be set to
automatically swept and the results can be plotted by connecting an x-y recorder to the (rear-panel)
Y
X AXIS and
An additional parameter related to ac level is gain, and more often, gain vs. frequency. To make a gain
measurement, measure the input to the device, then the output, and take the ratio. This measurement
is
made easier by the Audio Analyzer when used with
input level, then either measure
ratio reference. Then measure the output. The result can be expressed in either
the input can be swept and the gain plotted
logarithmically, the result
AXIS outputs.
by the press of a button (the RATIO key). Third, the measurement can be
it
and set it as a reference (press RATIO)
is
a Bode magnitude plot if
is
the variation in level vs. frequency (flatness). Of course
1V)
at a particular frequency (such
is
its
internal oscillator. You
as
a function of frequency (since the frequency plots
dJ3
is
used).
as
assumed
first
or
key in the
1
kHz) and monitor
to
be flat; otherwise,
key in the desired
level
as the
’%
or
dB.
If desired,
Model
Frequency
8903B
General Information
Another common and basic measurement
time interval between like points on the repetitive waveform and take the reciprocal. With
is
counter, frequency
much more accurate than could be made visually with an oscilloscope.
The Audio Analyzer contains a counter which displays the frequency of the input signal for all ac
measurements.
the signal (as you do with an oscilloscope) and computes the reciprocal
advantage of this technique
measurement time.
DC
Level
Although not part of an audio signal, dc level
example, bias voltages and outputs from ac-to-dc converters). Sometimes plots of dc level vs. frequency
(as
are desired
The Audio Analyzer has dc level as one of
in the case of
measured electronically and displayed. The measurement
It
should be noted that the counter
is
that for low (audio) frequencies, higher resolution
an
ac-to-dc converter).
is
frequency. With an oscilloscope, you simply determine the
is
easier and usually
is
a reciprocal type; it measures the period
to
obtain the frequency. The
is
obtained in a shorter
is
a quantity often encountered in audio equipment (for
its
measurement modes.
Signal Impurities
Distortion, SINAD, and signal-to-noise ratio are used to describe the impurity content of a signal.
These terms are somewhat related and
is,
sinusoid, that
are not always undesirable. Impurities, for example, are what add character
instruments. Pure
a pure signal is applied
is
degrading the signal. There are several common classifications of impurities: harmonic distortion
(harmonics of the fundamental), intermodulation distortion (beat signals of
signals), noise (random signals), and spurious signals (for example, line hum and interference). All but
intermodulation distortion are easily measured by the Audio Analyzer.
one whose frequency spectrum contains only a single spectral component. Impurities
signals
in music sound monotonous. However, when testing a linear audio system,
to
the input, anything but a pure signal at the output indicates that the system
can
often be confused. A pure signal
is
defined
to
the sound of musical
two or
as
more non-related
a
frequency
a perfect
of
if
Distortion
Harmonic distortion on a spectrally pure signal is created by non-linearities in the circuit through
it
which
running the active device into saturation
signal level, filtering,
According to Fourier mathematics, the non-linear terms in the circuit’s transfer function give rise
harmonics of the signal. Total harmonic distortion (THD) is usually defined
sum of the harmonics to the rms level of the fundamental. The ratio
An oscilloscope gives only a rough indication of the amount of distortion present on a signal. A general
rule of thumb is that if the non-linearity causing the distortion
a trained eye can discern distortion as low a
examples of waveforms with
distortion would be considered quite high in a quality hi-fi amplifier.)
An audio spectrum analyzer, which allows the user to see the magnitude of all harmonics,
the best instrument to measure harmonic distortion. The audio spectrum analyzer method, however,
requires a fairly expensive instrument and some mathematical manipulation.
passes. The non-linearities can arise in the transfer characteristics of the active devices
or
cutoff. Often, distortion can be reduced by reducing the
or
adding negative feedback.
as
the ratio of the rms
is
is
“gentle” (for example, not clipped),
5%
on an oscilloscope display. Figure
5%
THD and the components that combined
usually converted
to
produce them.
to
1-6
shows several
7%
or
is
perhaps
or
dB.
(5%
by
to
1-13
General Information Model
8903B
SIN X AND
SIN
X
+
0.05
SIN X AND
0.05
SIN
0.05
SIN
SIN
2X
2X
3X
SIN X AND
SIN
X
+
0.05
SIN X AND
0.05
COS
0.05
COS
2X
COS
3X
2X
SIN
X
+
0.05
SIN
3X
Figure
1-6. Several Waveforms Each With
The traditional method
is
with a distortion analyzer. The method
of
measuring distortion (accepted by the Institute of High Fidelity and others)
5%
THD
is
analyzer, you simply measure the signal level and set
of
tuned to the frequency
the fundamental, and measure the’output of the filter relative to the input.
This is the method used by the Audio Analyzer in the DISTN mode where the tuning and measuring
are done automatically. When using the distortion analyzer method,
is
the measurement result
not “total harmonic distortion” as defined above except under the condition
that the distortion is not too excessive but that it does predominate over any other signal impurities.
Some examples will illustrate these restrictions.
The Institute of High Fidelity, Inc., Standard Methods
High Fidelity, Inc., New
1-14
York
(1978),
p.
9.
SIN
X
+
0.05
COS
3X
and the Signal Components Which Produced Them
simple and adequate for most situations. With a distortion
it
up
as
a reference, then you insert a notch filter,
it
is
important to understand that
Of
Measurement
For
Audio Amplifiers,
The
Institute
of
Model
8903B
Consider the case of excessive harmonic distortion. Let us use the example of a signal with 10% actual
total harmonic distortion in which all the distortion comes from the second harmonic. The second
is
harmonic
measured by a distortion analyzer, an error results from the first part of the measurement (measuring
the input level) because the input level is not quite the same
the fundamental level were 1 Vrms, the second harmonic level would be
fundamental). The total input level (measured with a true rms voltmeter)
components, namely,
or
0.5% high. Thus, the measurement result would be 9.95% distortion instead of the true 10%. Actually
you can see that the distortion must really be excessive to affect the measurement significantly.
Now consider the case where other types of impurities are significant. Suppose the actual total harmonic
distortion
level. The distortion measured by a distortion analyzer will be 1.4% (that is, 40%
then, can you be sure that the result is a valid measurement of distortion? One way
(rear-panel) MONITOR output with an oscilloscope. If the waveform
to the fundamental, the measurement
are provided to remove unwanted signals. Use the optional 400 Hz High-Pass Filter
hum. Use the
filters that do not affect the fundamental and the harmonics of interest. Sometimes
include hum and noise as part of the “distortion” measurement. For this reason, the measurement
often referred to as a THD + N (total harmonic distortion plus noise) measurement.
then 20
is
1%
dJ3
below the fundamental as viewed on
Input
=
,/(1)2
+
(0.1)2
but that there is an additional hum component that has a level
is
actual total harmonic distortion.
30
kHz
or
80
kHz Low Pass Filter
to
remove out-of-band noise. However, select only
a’
spectrum analyzer. When this signal
as
the level of the fundamental.
=
1.005V
is
clean and harmonically related
0.1
If
General Information
Vrms (one-tenth of the
is
the rms sum of the
1%
of
the fundamental
or
3
dB
high). How,
is
to observe the
it
is not, selectable filters
to
remove line
it
is
desired to
is
If
two
is
SINAD
For most practical purposes the SINAD measurement, as made by the Audio Analyzer,
It
reciprocal of the distortion measurement.
that the notch filter
the signal at its input). This permits measurements in the presence of large amounts of impurities and
assures that the fundamental is tuned out.
frequency setting of the internal source.
SINAD is an acronym for SIgnal, Noise, And Distortion. The ratio (normally expressed in
computed in the
SINAD
The equation eliminates the
SINAD is used most often in determining the sensitivity of a receiver. Receiver sensitivity
as the RF level that, when modulated in a specified manner with a pure audio tone, creates a certain
SINAD (usually 10
noise.) Sometimes a psophometric (that is, noise measuring) filter is required in the receiver sensitivity
measurement. Optional plug-in weighting filters modify the frequency response of the Audio Analyzer
with a bandpass characteristic that approximates the response of human hearing. Weighting filters
which meet most international standards are available.
is
coarsely programmed to the frequency of the internal source (but fine tuned to
SINAD
measurement
=
20
or
12
dB)
rms value
log
two
rms value
restrictions discussed in connection with the distortion measurement.
at the receiver’s audio output. (The tone can just be discerned in the
is usually expressed in
If
an external source is used,
is
of
signal, ndse and distortion
of
ndse and distortion
dB.
The one subtle distinction
it
must be within 5%
is
equal
is
defined
to
of
dB)
the
is
the
Signal-to-Noise Ratio
Measurement of the signal-to-noise ratio requires the use of the Audio Analyzer’s internal source. The
off
Audio Analyzer simply turns the source (set to a specified level) on and
is
for both conditions. This
comfortable volume, then lifting the tone arm and listening to the level
similar to the experience you have when listening to a recording at a
and measures the ac level
of
the residual hiss and hum.
1-15
General Information
Internal Source
Model 8903B
The internal source
is
distortion
permits measurements
about the same
is
used when a low-distortion stimulus
as
that
of
the
Audio
Analyzer’s measurement system. The combination
of
distortion
as
low as
0.003%
(-90
for
the device under
dB).
test
is
Plotting
When used in conjunction with the sweep mode, any of the measurements vs. frequency can be plotted
using
the rear-panel
stimulus. This simplifies traditionally time consuming measurements such as flatness, gain, distortion,
and SINAD vs. frequency,
be used via HP-IB).
X
and
Y
AXIS outputs and
and
does not require the use
an
x-y recorder. The internal source is used as the
of
an external controller (although this
desired. Its
too
can
1-16
Model
8903B
General Information
lhble
All parameters describe performance in automatic operation or with properly set manual controls with a 1/2hour warmup
period.
1-1.
Specifications
SYSTEM SPECIFICATIONS
(1
of
5)
I------
Characteristic
DISTORTION
Residual Distortion and
Noise
(the higher
80 kHz BW
500
SIG/NOISE
Frequency Range
Display Range
Accuracy
Input Voltage Range
Residual Noise (the
higher of)
of):
kHz BW
Performance Limits
-80 dB or
-70
-65 dB or
50
0
f
1
50
-85 dB or
-70
17
pV
dB or
50
pV
50
pV
Hz to 100 kHz
to 99.99 dB
dB
mV to 300V
17
pV
dB or 50pV
20 Hz to
20
Hz to 50 kHz
50
kHz to 100 kHz
80 kHz BW
500 kHz BW
SOURCE
20
Conditions
kHz
FREQUENCY
Range
Resolution
Accuracy
OUTPUT
Range
Resolution
Accuracy
Flatness
Distortion and
Noise (the
higher of)
Impedance
SlNAD
Fundamental
Frequency Range
Display Range
Accuracy
Input Voltage Range
LEVEL
20 Hz to
0.3% increments
0.3% of setting
0.6 mV to 6V
Better than 0.3%
f2%
f3% of setting
f5%
f0.7%
f2.570 (f0.22
-80
-70
-65 dB or 38pV
6000
20 Hz to 100 kHz
0 to 99.99 dB
fl
f2
100
of setting
of setting
(f0.06
dB or 15pV
dB or 38pV
fl%
dB
dB
50 mV
to
kHz
dB)
dB)
or
500
300V
Open circuit
60 mV to 6V; open circuit;
6 mV to
0.6
mV to 6
20
Hz to
20
Hz to
20
Hz to
20
Hz to
50
kHz to
f2%
MEASUREMENT
Front-panel selectable
20 Hz to
20
kHz to
20
Hz to
50
kHz
6V;
open circuit;
rnV;
open circuit;
20
kHz; 1 kHz reference
100
kHz; 1 kHz reference
20
kHz; 80 kHz BW
50
kHz;
500
100
kHz; 500 kHz BW
20
kHz (unfiltered or with low-pass filters)
100
kHz
20
Hz to
kHz BW
(HP-IB)
100
20
Hz to 100 kHz
kHz
Residual Noise and
Distortion (the
higher of)
rev.
30DEC88
-80 dB
-70
-65 dB or
or
dB or
15
45
45
pV
pV
pV
20
20
50
Hz to
Hz
to
kHz
20
kHz; 80 kHz BW
50 kHz;
to
500
100
kHz; 500 kHz BW
kHz
BW
1-17
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