HP 3575A User manual

t:
OPERATING AND SERVICE MAttIUAT
MODEL 3575A
GAIN.PHASE M ETER
Scrial Number: 1.150A016.16
IMPO BTANT NOTICE
Th s loose leaf rnanual does not require a change sheet. All change information
has been inteqrated into rhe manual by meansof r-"vised pages Each revised page
rs denlified by a revsion letler located al the boltorn of the page. A reference,
locared directly below the revislon lerter, indicates which of the backdating
changes in Appendix C apply to that page. lf the serial number of yoLrr
nstrurnent rs lower than the one on this title page, the manual contains revisions
thar may nor appy to your nstrument. Refer to Appendix c for complete
birck dat ing information.
-hp' Port No. 0.1575'90002
(Completc Ilanual includins Binder)
Nlicrofiche No. 0-3 575-9005.1
Ci)pyright HervlettJ']ackard Conrpanl' 1972
P. O. tsox 301. Lovclund. Colorado 80517 U. S. A. MA
P nted: June 1976

HEWLETT ;hE
aPACKARD
CERTIFICATIO N
Hewlett-Packdrd Company ccrtifies thdt tltis instrutterrt tnat its publislrcd
specifications .tt the time of shipment fron the factory. Hewlett-Packard
Company further certifies that its calibrdtion medsuremetlts ure trdceable to thc
United States National Bureau of Standards, to the extott allowed by the
Bureau's calibration facility, and to the calibrution facilities of other
lnternational S t dndard s Organi: at io n me mb er s.
WARRANTY AND ASSISIANCE
This Hewlett-Packard product is warranted against defects in materials and
workmanship for a period of one year from the date of shipment, except that
in the case of certain components, if any, listed in Section I of this operating
manual, the warranty shall be for the specified period. Hewlett-Packard will, at
its option, repair or replace products which prove to be defective during the
warranty period provided they are returned to Hewlett-Packard, and provided
the proper preventive maintenance procedures as listed in this manual arc
followed. Repairs necessitated by misuse of the product are not covered by this
warranty. NO OTHER WARRANTIES ARE EXPRESSED OR IMPLIED,
INCLUDING BUT NOT LIMITED TO THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.
HEWLETT-PACKARD IS NOT LIABLE FOR CONSEQUENTIAL DAMAGES.
lf this product is sold as part of a Hewlett-Packard integrated instrument
system, the above warranty shall not be applicable, and this product shall be
covered only by the system warranty.
Service contracts or customer assistance agreements
Hewlett-Packard products.
For any assistance, contact your nearest Hewlett-Packard
Office. Addresses are provided at the back of this manual.
are available for
Sales and Service

Modcl 35 75A Table of Contents
TABLE OF CONTENTS
Scction Page
I GE\ER.{Ll\FOR\lATIOlr- .......1-l
I'1. Descripti,ri ......1-l
1-10. Sp!'.ilijJllons .............1-i
1-l -i. Optioni ......... 1-l
l-16. Acce:sLrrie: Supplied . .. . . .. .l-4
l-18. .-\.i.ssori.: \rrilrble . ....... l'1
1-10. Inrrrunr.'nt lnrl \llnull Identificrtion ... . 1".1
Section
II I\ST{ LL \TIO\ A\D I\TERFACING 1.37.
4.48.
.+-5 3.
1.57.
.1,66.
.1-69.
.1-96.
l-r. I ,'r . I,. .f-- ., .
1,5. Ptr* c r Requrr.'mcnts
2-1 P rr< (s11.
2.q. Cr.J.r.Jrr,- R< luitrrn<n .... .. ...
2-l l. Ertrr ,r m. r. . I Rc.1 ri,rmcnr. . . . . .
2- 13. InstrlLr i',n
2-l-1. B. r .', \!. ..tr,t.rr:
2-16. R:.'k \lounting
2-18 Rep,.L.-.r,t i. Slrrpmcrrr
2-ll. Iu., :,.r'- rOpr ,rr 00J.00J) ...... ..
2-15. C,),npur.r Int"'rircing
2-:7. Prr. lr.tr"Jur..l
Section Page
III OPERATI\G I\STRL'CTIOI,iS.... , ... , ,., . .3-I
3'1. In lrodu. rir,n . . . . . . . . . . . . . . 3-l
3-3. Ctrntrolr rn,l Indicrtors . ....-l'l
3-5. Gc'rlerul Op.raliig Inft)rmation . .. .. .. . .3-l
3-6. lnput Conn.ctions ........3-l
3-8. GrounJingandTerminatiorl .........-l-l
3-19. InpurClinsrraints ..........1-5
3-2.1. \'oltes.Runses ..........-l-5
3-)7. Frrquen$ Ranges.. ......3-5
3--10. \l!'1.rInJi.i11ion .........3-5
3--17. Anrlo!Outpuls ..........3-6
3-.11. Basi. OperrtinuProcedure ............. 3-6
3-1)- l 5trunl.,rt Turn Ol .. ... ..... . ... .3-6
-3-.13. AmpirruJ.'\lcasurernents ...........3-1
3-48. Phrse\leasurements ...............-l-8
3-59. Lsins i0:l Divider Probes .. . .. .. .. .3-10
3-64. Oprions ........-l-ll
3-65. Op.rol 001 .... ... ..3'll
3-11. Oprjon00l.003 .........3'll
3-87. Using r Pnnter . .. ... . . ... -l'1.1
3-89. Trisg.nn! . ...3-1.1
-l-91. Print,rut . . ...3'14
Section Page
V MAINTENANCE . . . . , . -...,....5.1
5-1. lntroductiolt . . . . . . . . . . . . . .5-l
5-,1. RccommendedTestEquiprnent.........5-l
5-5. Perlbrrnance Checks .. ......5-2
5-7. Test Card . ... .... . .... ..5-?
5-9. Panel Meter Accuracy Check .........5-2
5-ll. Amplitude and Phase Accuracy Checks . 5-3
5-13. High Lgvel Accuracy Checks . .... . ...5-6
5-15. Shunt Capacitance Check ......... .5-6
5-17. Supplellrental Phasc Accuracy Chcck . . .5-7
5-19. AdjustmentProcedures ......5-9
5'll. Test Equipment ..........5-9
5-13. Tcst Point and Adjustnrcnt Location . . .5-9
5-15. + l2 V Rclerence Adiuslrllcnt ........5-9
5-:7. Power Supply Voltagc Chccks . . . . . . . . 5-9
5-19. Output FiltcrZero Adjustmcnts ...... 5-9
5'31. Panel Mcter Zero Adiustnrent
(Standard&Optio[s)...... .. .....5-10
Phasc Detcctor Zcro Adjuslnrcnt.. . . . . .5-10
Curre0t Source and Current
Srrrk Adlu:trnent.
Pancl Nlctcr/Anaiog Output
A,llrrstrrrerrt>.
AmpliruLle Oltscl AJI r.lnrerl .......
I .rg A rrr plite r AJltr:ttrtctt 1..
..4-r0
..........4-l l
5-35.
s-3 7.
5-U9
5-11 .
.5-10
.5-1 1
.s-1I
.s.1 1
lll

Table of Contents
Section
V 543. Input Attenuator Adjustments . . . . .
545. High Frequency Phase Adjustments . .
547. High Frequency Log
AmplifierAdjustment ..........
549. Factory Selected Components. .....
5-51. GencralServicinglnformation. . . .. . .
5-5 3. Caurions
5-55. Assenbly Removal .
5-65. ComponentReplacement.
5-67. Servicing Etched Circuit Boards. . . . .
5-70. Cleaningthe Display Window ......
5-72. Troubleshooting . . . . .
5.74. Cuidelines.
5-76. Syrnptoms.
5-78. Tr,-rubleshool inB Trees.
5"82. MeasurementConditiotrs
5-84. Control Settings . .
5-86. Power Supply Troubleshooting . . . . .
TABLE 0F C0NTENTS (Cont'd)
Page
. .5.12
..5-12
. .5-13
..5-14
..5-15
. .5.1 5
..5.15
. .5.16
..5.16
..5.16
..5.18
..5.18
..5.18
..5-18
..5-18
..s-18
. .5.r 8
Section
VI REPLACEABLE PARTS
6-1. lntroduction .... ..........6.1
64. Ordering Information . ......6-l
6-6. Non-Listed Parts . . . . .......6-l
6'8. Proprietary Parts . . . . .......6-1
Model 3575A
Page
. . 5 -,i
..5-l
..5.E
APPENDICES
A. CODE LIST OF MANUFACTURERS
B. SALES AND SERVICE OFFICES
C. BACKDATING
Figure Page
l-1. Model 3575A Gain-Phase Meter . . . . . . . . . . . . . . 1'0
2-1. Power Cords ..........2-l
3-1. Front Panel Description ...........3-2
3-2. Rear Panel Description ...........3-3
3-3. Power-Line Ground Loop .........3-3
34. Source-Induced Ground Loop .... ...........34
3-5. Power lnput Module A, B and C . . . . . . . . . . . . .3-j
3-6. dBV to Volts Conversion ..........3-8
3-7. Worst Case Error Produced by
Odd Harmonics .......3-9
3-8. Simple RC Network . . . . . . . . . . . . . .3-9
3-9. Remote Pin Connections .........3-12
3-10. Flag Timing Delayed Mode .......3-14
3-1 1. Flag Timing Non-Delayed Mode .. . . . .. . . .. .3-14
4-1. Simplified Block Diagram .........4-l
4-2. Phase Difference + 60 Degrees . . . . . . . . . . . . . . . 44
4-3. Phase Detector Output .. ... -.... .44
4-4. Phase Control Filter Output . . . . . . . . . . . . . . . . 4-5
4-5. Basic Filter CDnfiguration .........4-5
4-6. Phase Control Logic Functional Block
Diagram . ... -.... .. . -4-6
4-1. Logic Gates... -.......1-7
4-8. Aand BInPhase -No Distortion . . . . . . . . . . . . . 4-8
,1-9. Even Harmonics Cancelled . .. . ... ..4-9
4-10. A and B Clean - No Error ..-.......4-9
4-11. l-arge Error Produced by Noise . ... -.. -......4-9
4-12. Panel Meter Block Diagram . ......4-11
4-13. Analog and Digital Timing ...,,.4-13
Figure
4-14. Timing Circuits and Functional
Block Diagram
5.1 . Power Splilter. . .
5-2. Arnplitude and Phase Accuracy Checks . . . . .
5-3. Shunt Capacitance Check
54. R/C Phase Shifr Network .
5-5. Removing the Front Panel, Panel Meters
andAl2 . ........5-17
5-6. Location of Main Assemblies and
Adjustments ,...5-21/5-12
5-7-" Location of Panel Meter
Adjustments ... .5-2115-22
Amplitude TroubleshootingTree ........5.23'5.:4
Dig.ital Panel Meter Troubleshooting Tree .5-25/5-26
Phase Troubleshooting Tree .. .5.27'5.28
Phase l,ogic TroubleshootingTree .......5-29/5-30
Mechanical Parts (Main Frame) . . . . . . . . . . . . . 6.17
Mechanical Parts (Panel Meter) . . . . . . . . . . . . . 6- 1 9
Functional Block Diagram ......7-5 7-o
Preamplifier (Al/A2) and Log Converter
(A3/A4) Schematics and Component Location
Diagrams . ........7-711-8
7-3. Phase Detector (A5) Schematic
and Component Location Diagram . . . . . . 7 -9 l7 -10
7-4. Current Source (46) and Phase Control
Logic (Al 1) Schematics
and Component Location Diagrams .....7-ll 17-12
7-5. Phase Control Filter (A7) Schematic
and Component l-ocation Diagram .....7-1317-14
LIST OF ILL USTBATIO NS
5-8.
5-9.
s-10.
5-11.
6.1 .
6-2.
'7-1.
7.2.
1V

Model -1575A
Figure
7-6. Funct r.,n Srr1l.hrnS(A8)and Front
Pin.'l S\\ itihinr ( .\ I -l ) Schematics
rnd C(rrrp!)ianI L!)calion Diagrams . . .
7-7. Ourpul Fiher r.\') Al0) Schematic
and Conrpr,n.'nt LLrclrlion Diagram . . .
7-8. Pan.'1 \leter t \10. Al 1. A21) Schematics
rnd Conp.,nen t L,rcltion Diagranrs
Figure Page
7-9. Powcr Supply (Al4) and Power Supply
Mother Board (Al5) Schematics
and Component Location Diagrams .. .. .7-2111-22
7-10. Interface Board (Al68) Schenratic
and Conrponent Location Diagram .....7-2317-21
7-l l. Panel Meter Connector (Al 2A, A l2B) Schcmatics
and Component Location Diagrams . . .1-2517-26
LIST 0F ILLUSTRATI0 NS (Cont'd)
Page
..7-ts11-t6
. .7-t7l7-t8
.7 "1911-20
Tahle of Contents
Page
. . .4-t8
....5-l
....5.5
....5-6
....5-9
...5-1.1
...5,19
....6-2
....1-l
LIST OF TABLES
Table
l-1. Spe. it.;r t .
l -2. General lnlornlalion
l-3. A.'ir...,r c5 Supo .(J
l -4. A(.(r.,rrrc] \\,il,bl- ........
3-1. lrpiurl setL.. -' [.nrc ....
3-2. Eiicit' \ ,r.c \lr'.rnrzcd
j-j. ReJ..,1.,..1 l,pFpruhL, ....
J-,1. Prirrre-C, l.lr:rrr r C.,Jrrr- ... ..
3-5. Prrrrtir (",1 1'1111 ,., t-, Jr,: .
4-1. Filter C.,r.t- . I.,-ri
1-2. nre.lr 'rJ D(r,.r. r Ou-pLrt . . . .
,l--1. Err.rr C,,r'.'.r ' f.l,rrti, tr' .
4-4. Amplit u,ic F.lrcrion Siritching
Page
.,.,1{
....r-).
....11
.. . . t4
....3-5
....1,9
... -t- 10
...3-15
. . .3-15
....1.6
....4.1
....4-9
. . . 4-10
Tabie
-1.5. Panel \,letcr Suitehing L,'rii .......
.l-6. Variable Time Delays
5-1. Recommerlded Test Equipment.....
5-2. Amplitude and Phase Accuracy Checks
5-3. High Level Accura(y Clreck. . . . . . . .
5.,1. P,,wcr Suppll Checks
5-5. Fr.'t,rr1 Selectcd Component. . . . . . .
J r'. P,,vys1 Supply Rating:
'.-1. ReplarcahleParls....
7-t .
7-2.
7-3.
Assembly Cross Relerence .......
Morher Bo.rrd Pin Conne.tions . . . . , . . , . , .7-31'74
7 -2317 -24
Truth Tahle for Remote

Section I
3575-A-2843
'r.,, ,;i[ ; '{ir
&w{e
;t
Figure 1-1. Model 35754 Gain.Phase Meter.
Model 3575A
Table 1-1. Specifications.
PER FORMANCE RATING
Phas6 Accuracy (At Analog Outpur)*
Amplitude Accuracy (Al Analog Output)+'
'Conditions:
'l) Temperature Range 15o to 35o C.
2) Lowest applicable Voltage Range settings must be
3) Lowest applicable Frequency Range s€tting must be
4) Analog Output Voltage-10mV per degree with
> 2 Megohm load resistance.
5) Phase Stability and Accuracy is specified for a period
o{ 90 days;fter calibrarion.
**Conditionsl
1) T€mperature Range 150 to 35o c.
2) The accuracy of ratio (B/A) measurements is deter-
mined by the lowest input level and highest input
frequency. lf the two input signals are nol of the same
frequency, add I 0.5 dB to existing ratio tolerances.
3) Analog Output voltage = 10 mV per dB/dBV with
> 2 I\,4egohm load resistance.
4) Amplitude Stabi,ity and Accuracy is specified for a
period of 90 days after calibration.
Panel Meter Accuracy: t 3 counts (0.3 degrees, O.3dB/dBV)t
tl!4ust be added to Amplitude Accuracy and Phase Accuracy
specifications to obtain total error tolerances for panel
meter readings.
Input Shunl Capacilance: < 30 pF (Also see lnput lmpedance
listing in Table 1-2.)
t-0

Model 3575A
I
Sectiorl I
SECTIO N
GENEBA[ INFOR ATION
dBV (l V rms = 0 dBV). Input levels from 0.2 mV rms
(" 74 dBV) to 20 V rms (+ 26 dBV) can be measured with
0.1 dBV resolution in two voltage ralges. When bg B/A is
selected, thc panel rneter indicates the relatiye amplitude of
the two input signals in dB. The display range for relative
measurements is from - 100 dB to + 100 dB with 0.1 dB
resolution. Since the two input channels each contain ac/dc
corverters and are totally indgpendent, relatiye measure-
ments can be made between two signals that dilfer in
frequency.
1-7. The 3575A amplitude functions are particularly useful
fbr measuring gain, attenuation and other characteristics
where amplitude comparison is required. The I-og B/A
function eliminates the need for separate input and output
measurements and time conslming difference calculations.
1-8. Mlen Phase Dsplay is selected, the 35754 measures
the phase difference between two input signals. The phase
measurement range is from - 180 degrees to + 180 degrees
with 12 degees overrange and 0.1 degree display reso-
lution. Due to the wide dynalnic range of the instrumelt,
phase difference can be measured between two signals that
differ in amplitude by as much as 100 dB.
l-9. An accurate phase meter is of little value unless the
accuracy oan be maintained in the presence of troise and
distortion. Udike conventional phase meters, the 3575A
uses two phase detectors rather tian a single phase
detector. This, in conjunction with a highly effective error
correction scheme, greatly reduces the elfects of noise and
distortion on phase readings.
1-10. SPECtFICATT0NS.
l-11. Table l-1 is a complete list of the Model 35754
critical specifications that are controlled by tolerances.
Table l-2 contains general information that delcribes the
operatirg characteristics of the Model 3575A.
I-12. Any changes ill specifications due to manufacturing,
design, or traceahility to the U.S. National Bureau of
Standards are included in Table l-l in this manual_
Spscficatiols listed in this manual supersede all previous
specfications for the Model 3575A.
1.13.0PTr0NS.
1-1.1. There are presently three instrument and two acces-
sory options available for the Model 3575A. These options
are as follorvs:
I
M
1.1. D ESCRTPTT0 N.
1'1. The Hewlelt-Packard Model 1575A Gain-Phase Meter
is a versatile. wide-range ac voltage analyzer which affords
diect. convenicnt mcasurenent of amplitude and phasc
paranletcrs. Thc nrajur featurcs of the instrument includg
broadband fiequertcl response, wide dynamic range, digital
readout plus a unique detgction soheme which ensures
accurate phase measuremcnts in the prescnce of noisc artd
distortion. These standard leatures, along with a variety ol
options including dual panel meters, BCID output and
remote control. nrake ths -3575A a truly flexible instrurnent
that is well suited for bench or systems applications.
l-3. rhc broadbrnd liequency response of the Model
3575A extends frorl I Hz to l3 Nlllz in four overlapping
frecluencl' rartges- For JnaxiJnum operating corlvenience,
each range is designed to cover a wide band of frequencies
while range seleciability allows the user to optinrize
measuremenl accuracv ar:d scttling tinle over the entire
frequencl spe{l.unr.
l-4. The -1575A is equippcd with two independent input
clunnels. Each channel provides an lJodB dynamic range
which allorvs "hands ,rff" operatioii with a wide range of
input levels. In addition, each channel is equipped with a
20dB input attenurtor rvhich provides an extended oper-
ating capabiiit) ol 100 dB in two voltage rangcs. Input
sensitivity is fron 0.] mV rnrs b l V mls on the lower
range and I mV nrrs to 20 V rins on the higher range. The I
Megohm ( 30 pF input impedance of each channel permits
the use of l0:l divider probes which further extend the
]rl&rinum input level to ]00Vrms and the overall oper-
ating range to I 20 d B.
l-5. The i575A.ontains a buiit-in dc digital voltmeter
which providcs ! direcl indication ol amplitudc or phase on
a 3 l/2 digil (LLD) display. Lighted annunciators oo the
panel rlletcr indicatc dB V, dB or degrees dependinB on the
paranreter being rneasured. Thc pancl nrctcr displa) is deter-
nlincd b) thc iiont panel Displa) switch rvhich permits
selection oi AurplitLrde or Phase presentatiorl. For recording
purposcs. ar1 Analog Output (BhvC) connector is providcd
on the rear panel ol thc instrument. The Ana)og Output
supplies a dc voltage proporlional to the panel nteter
reading.
l-6. Wren Amplitude Display is selected, the panel Ineter
presentation is controlled by the ftont panel Amplitude
Func'!io11 switch which permits selection of three different
functiols. These tunctions are Log A, Log B and Log ts/A.
When Log A or Log B is selected, the panel meter indicates
the logarithrnic amplitude oI the respectiye input signal in
1-l

Section IModel 35 75A
* Field installable option kits are av6ilable.
** Options 002 and 003 are identical
except for assertion states of BCD
ourp(s (se€ Table 1-2).
Option Factory lnsralled*
Dual Panel Meters
Dual Panel Meters,
8CD Outputs and
Remote Control
Kit, Rack lvlount
Additio'ral Manual
Ofiion 001
Option 002
Optio'n 002,
003**
Option 908
Option 9'10
Table'l-2. General lnformation.
INPUTS
Fron! Panel lnputs: Female BNC connectors
lnput lmpedance: 1 [.4egohm (nominat) shunted ty < 30 pF
Rear Pan€l lnpuls: Holes are p,ovided on the rear panet for
installing BNC input connectors in ptace of rhe front panel
input connectors. When reaFpanel inputs are used, the shunt
capacitance increases to approximately 40 pF (not compat-
ible with 10:1 divider probes).
ANALOG OUTPUTS
Connecrors: Female BNC connectors, tabeted ANALOG OUT-
PUI 1 and ANALOG OUTPUI 2 are tocared on the rear
panel of the instrument. Analog Output 2 is used only in
instruments equipped with dual panet metsrs loptions OO1
and 002).
Resistanc€: 1 Kilohm {nominat)
Output Voltaq6:
Amplitude l!4easurements: 1O mVdc per dBldBV with
> 2 Megohm load resistance.
Phase Measurements: 10 mvdc per degree with > 2 M€gohm
load resistance.
RESPONSE TIME
Typical S6ttling Tim€: (rollowing a chanqe in
DISPLAY MODES
Amplitude or Phase {front panel DISPLAY switch)
AMPLITUDE MEASUREMENTS
Amplitudo F'rnctions: AdBV, BdBV, or B/A (front panel
AMPLITUDE FUNCTION switch)
Display Rango (AdBV, BdBV): -74.0dBV to +26.0d8V (in
two Voltage Ranges)
Display Rangs (B/Al: - 100.0dBto+ 100.0d8'
' Both input signals must be within the range of 0.2 mV rms
to 20 V rms.
Display Resolution: 0.1 dBV,0.'l dB
Amplitud€ Refer€nce (A dBV,BdBV): 1 Vrms=0dBV
R6f6ronce channel (B/A)i channel A'
' A neqative reading means that the signal applied to Channel
B is lower in amplitude than the signal applied to channel
A; a positive reading means that the signal applied to
Channel B is qreater in amplitude than the signal applied
to Channel A.
PHASE MEASUR EMENTS
Phas€ Measuremsnt Banger - 'l80 degrees to + 'l80 degrees with
'12 degrees overrange
Display Resolution: 0-l degr€€
Phss€ Referenco: A or -A (front PHASE REFERENCE
'1) Channel A is the reference channe,. A negative reading
means that B lags A;a positive reading means that B leads
'2) Wirh rhe Phase Reference set to "A, Channet A is
inverted and the phase reading is offset Lly 180 degrees.
Error lntroduced by Noise: < 2 degrees {nominal) for a I V
10 kHz sine wave and 1 MHz gaussian noise on one channel
with 30dB signal to noise ratio using the 100 Hz to I MHz
Frequency Range.
Error Introdrrc€d by Distortion:
Even Harmonics: Cancelled - No Error
Odd, ln+trase Harmonics: No Error
input parameters):
907.*
Seril.d
17 sec.
1.7 sec.
0.17 sec.
17 ms.
100%r
Se lad 95 0/o '
Seril6d
RANGES
Frequency Rang€: 1 Hz to i3lvlHz jn four ranges:
1 Hz'1 kHz
10 Hz - 100 kH2
100Hz-1MHz
1 kHz - 13 MHz
l H2 to
10 Hz to
100 Hz to
1 kHz to
30 sec.
3 sec.
0.3 sec.
30 ms.
20 sec.
2 sec-
0.2 sec.
20 ms.
kHz
00 kH2
MHz
3 MHz
Dynamic Range: 80 dB
Operating Range (Each Channel): 100 dBin two ranges:
0.2 mV rms to 2 V rms (, 74 dBV to + 6 dBV)
2 mV rms to 20 V rms (-54 dBV ro + 26dBV) Odd, Out-of,Phase Harmonics: < 0.6 degrees (nominat
when total odd harmonic distortion is more than 40d
below the fundamental
Percent of final reading
1-2

Model -i5 7-i.{ Section I
Table 1.2. General Information (Cont'd).
DIGITAL R EA DOUT
Reading Rate rlnrernal Sampling): 4 raadinqs per second
GENERAL
Display: -i : t r:: ,! ih frxed decimat indicator, po ariry sign
a.rd:---_.::r.:
Operating Ternperaiure Range
Storage Temperature .1Oo C 1
Power Requrrements I 15 V
440 H, a0 \'i ^-aximum
Net tle onr 13 : .1 bs
Shipp.|r , r,ir!i: :a bs
: 0o C to + 55o C, untess orher
o+75oC
or 230V i 10'\, 4aH2 b
In 3575A Option 003, 8CD Outpurs are H,qh True
8CD Outputs: Provide parallel trinarv.odecl data thst corre
sponds wiih the respecrive panel meter reading. Fo!rreen
lines for each panel merer ircl!de three 84 2I 8CD
coded disits, a singl€ lrne overange ('1") digit and a
sing le line poiariry indicaror.
Overload Outpurs: Three output llnes, AOL, BOL and
"overload", indicate overlo3d on A, overtoad on B and
overload on A OR B
Romote Contro Lines: Eighi input tines accept para
binary lnstructions for remote co trol of alt front
il obtain panel meter readi,rgs or BCD oulputs init
by the R€mote Measure command. tn the
mode the time is variable and is contro ed by
Frequency Ranqe setring:
functlons, raoses and sertLngs (excepr LINE ON/OFF)
lnterna storaq€ is not provided.
Conlrol lvlodesr Local or Remore (1 conlrot li.e)
Remote lUeasure: 1 conrrot tine'
' ln the Remole Control rnode, the panet meters mUst be
externally rriggered by apply ng a ground true momen
tary pulse (> 1 ors) to the Rernote Measure t,ne each
time E reading is reqLrired. The Remore f\4easure
command shou d nor be apptied for ai teast O 5 ms
following any change that affects rhe Droqrammed
state of ihe irrstrunrent
lsolation. R€more input.nd ourput lines are /1.)/ isotaled.
Trigger Mode: Delayed or Non Delaye.l (1 conrrot tine).
'The trigger mode determ nes the time required to
Delay Time (nominal)
OPIIONS
Dual Panel Merers (Oprion 0O1): The 3575A Option O0t is
eq! pp:d f,r!. du.i pane metersanddua anatog ourputs Ior
sim! tareo!s a..! r!de and phsse presenrarions.
Lefl.Ha.cr P:.. '!'eter tndrcates A dBV, B dBV or B/A as
deter-.-pd b! the A,np itude Funcrion switch seiting.
Righl Hard Pe". lrleler: lndicates B dBV or phase as deter
m red br ihe Ampt rude B/Phase swirch serrinq.
Dulr A.a oo Ourputs Re,rr panet 8NC connectors provi.l_-
dc ourprr vclrages rhat correspond wth rhe resOecrive
p.ner rr.1e. r!.€di.gs (a so see Anatoq Ouipur headino).
Dual Panel Meters, BCD Output and Remore Controt {Options
002, 003): The 3575A Options 002, and 003 are equipped
u/ith dLra p€.pi rn.lers and dual analog outputs ($me as
Optio. 001) p,!5 dual BCD outpuis and a complere remore
conrr ol caoabl tv
I
lHrtolkHz
l0 Hz ro 100 kHz
10O Hz ro 1 MHz
1 kHz ro 13 MHz 0 66 secords
ln the Non-Delayed mode, the rneasurement rime is
fixed at 600 ms regardlass ()1 the Frequency Range
serting-
Data Flags: + Data Flag and - Dara Flag (2 ourplr tines)'
'Provrde a "Data Readv" indication to the exrerna
controller. Flags are "set" by the Rernote [\4easur€
pulse and reset" a1 rhe erd of the d€lay lTriqqer
N4ode) cycle
Remote Loq c The 35754 Oplion 002 uses Low True TTL
logic lcr BCD outputs and remote controt tines. The
3575A Oprion 003 uses Hiqh True TTL toqic for BCD
Outpui! a.d Low True TTL logic for remore conrrol
"O' | +2.1Vto+5V I Openor*2.4Vto+5V
"1" | 0Vio+04V l Gnd.or.0.5Vro+0.4V
,z --r \
/.r,\
/il--r \
\ T li:; r / -
\ -*- /\ \.
fir----'') T rl
| !:r !j
l! ,n l
, i!
I-l

Section I
l-15. For further information concerning these options.
refer to Table l-2 (General Infonration) or &ction Ill in
this manual or contact the nearest -hp- Sales and Seryice
Olfice.
1.16. ACCESSoRIES SUPPUED.
l-17. Table 1-3 is a list cif accessories supplied with the
Model 3575 A.
1.18. ACCESSOBIES AVAILABLE.
t-19. Table l-4 is a list of Hewlett-Packard accessories that
are available for use with the Model 3575A.
1.20. INSTHUMENT AND MANUAT IDENTIFICATION.
l-21. Hewlett-Packard uses a two-section serial number.
The first section Grefix) identifies a series of instruments.
The last section (suffix) identifies a particular instrument
within the series. If a letter is included with the serial
number, it identifies the country irl which the instrument
was manufactured. If the serial number of your instrument
is lower than the one on the title page of this manual, refer
to Append8 C for backdating information that will adapt
this manual to your insfument. A]l correspondence with
Hewlett-Packard should include the complete serial
number.
Model 3575A
Table 1-3. Accessories Supplied.
Descrlption Ouanrry | .hp- Part No.
Inrerrd,p Connei ror I I ea. | 1251.0086
(Opt.002,003)
ac(Pssory <.r I I ea. I 03575-Ba4l l
lncludes the followlng
PC B^.,d E.renoo, r22 pin) | I ed. | 5060 5980
PC Bo"rd L rrpnoer r12 pin, | 1 ea. | 5060-5988
PC Bo"rd F rrende, r l0 oinr I 1 ea. | 5060-598 /
Table 1-4. Accessories Available.
'hp- Mod€l D6!cription
10004A
456A
562Al6C
11048C
1 1094 B
11095A
5060-8739
Voltage Divider Probe (miniature)
AC Current Probe
Printer Cable
(for 50504 and 50558 Printers)
50 Ohm Feed-Thru Termination
75 Ohm Fe€d-Thru Termination
600 Ohm Feed'Thru Termination
Rack Mountinq Kit
t4

Model 35 75A
2,I. INTRODUCTION.
2-2, This section contairs informatioD alld instructions
na:cssary for installing, shipping and interfacing the Model
3575A Cain-Phase trleter. lncluded are initial inspection
procedures, power and grounding requirements, environ-
mental information, mounting instructiol1s, inslructions for
repackaging lor shipment and interfacing information for
Option 001 arld 00-l instlumcnts.
2.3. INITIAL INSPECTION.
24. This instrument was carefully inspected both nlechani
cally and electrically before shipnrent. It should be physi-
cally free of mars or scratchcs and in perfect electrical ordcr
upon receipt. To confirm this, the instrument should bc
inspocted for physical damage incurred i[ transit. lf the
instrurnent was damaged in transit, file a clairn with the
carrier. Check for supplied aocessorics (Table l'3) and test
the electricai pcrforrrrance of the instrument using the
performance check procedures outiined in Section V. lf
there is danage or deficicncy. sec the warranty oll the
inside title page of this manual.
2.5. POWER B EOUIREMENTS.
2-6. The ltlodel 3575A can be operated from any source of
ll5 or 230 volrs (1 l0%), 4t{ Hz to 440 Hz. Power
dissipatiol is 50 VA: nlaximum.
2-7. Power Cords.
2-8. Figure 2-l illustritcs thc standard power plug cotrfig-
urations that lrc used throughout lhe United Stxtc! xnd ili
orher countriqs. The -hp- part number shown directli, below
each plug drawing is tlie part numbcr foL a 3575A powel
cord equipped with thc propcr plug. ll the approprirte
power cord is not lncluded witlt the insttumcnt. notlfl thr'
nearcst Hcwlctt-PilckaLd olllcc and a replacemcnt cord will
be provided.
sEcTl0N il
INSTATLATION AND INTEBFACING
Section I
,.n: - 125 V 64" 250 V 64'
ri -,] :ttr'7-1'':i-.,-,'',,a'.,..... I \,
..,,..,+,,1, t ;j'i-".,,.," =r'..\
8t20- 35 8r20-t369 8t20 16A9 8120-1348 8120-0698
rUL LISTEO FOR USE ]N THE UN ITEO SAATES OF AMERICA
2.9. GBO UNDING BEOUIREMENTS.
2-10. To protect operating personncl. the National Electri-
cal Manufacturer's Association (NEMA) recomrnends that
the instrumcnt panel and cabinet be grounded. The Nlodel
3575A is equipped with a three-conductor power cable
which, when plugged irto ar) appropriate rcccptacle,
glounds the instrunlent. Thc oliset pin on the power plug is
the ground connectior.
2,11. ENVIRONMENTAL BEOUIHEMENTS.
2'12. The Modcl 3575A is a low powcr. fully transistorized
instrunlent; thereforc. no special cooling arrrlgements arc
requiLed. The 3575A should not be operated where thc
ambient tempcraturc is below 0'c (32"F) or above 55'C
(13t" F) or where thc relative hurnidity exceeds 95%. The
instrumcnt should ttot be stored whcre the ambient
temperature is below '.10'C (-40" F) or above 75'C
( 1 6 7'F).
2.13. INSTALLATION.
2-14. Bench Mou nting.
2-15. The Model 3575A is shippcd wjth pllstic fecl and tilt
stand in plilce, ready for usc as a bcnch instrumellt. The
plastic leel a|e shaped so that the 3575A can be lnountcd
on top of anothcr Hewlett-Prckard instlumcnt.
2-16. Hack Mounting.
l'17. The Nlodel 3575A ca be tack rnounted usirtg the
Rack Mounting Kit ({p- 5060'8739) separately available
as an accessory. Installatioo instructions are included with
tllc kit. The rack mount for tlrc Model 3575A is an EIA
standard widtlr of l9 incires.
2.18- REPACKAGING FOR SHIPMENT.
2'19. The following paragraphs conlain a gcncral guide for
repackagiiS the instrument lbr shipment. Rcfer to Para-
graph 2'20 if the original contriner is to be used;2-21 ilit
is not. II you have any questions, contrct the nearest -hp-
Sales and Service Ofllce (See Appendix B for office
locations ).
NOTE
lI the instrunlcnt is to ba shipped tu Hawlett Packard fir
servir:e or repair, qttuch a tag to llrc i strunent lentif)'ing
the owner atll indicqti g the servirc or repoir to be
accomplished. lnclucle the nodel nuntber antl full serial
nurnber of tlrc i$tntmenL In any correspontlence, idefitify
the instrunrc t br nodel number arul full sarial truntber.
Fisure 2-1. Power Cords.
2-1

Section ll
2-20. Place instrument in original container with appropri-
ate packing matcrial and seat well with strong tape or metal
bands. If original container is not ayailable, one can be
purchased from your nearest -hp' Sales and Service Office,
2-21. If original container is not to be used, proceed as
follows:
a, Wrap instrument in healy paper, or plastic before
placing in an inner conlainer.
b. Place packing material around all sides ofinstrument
and protect panel face with cardboard strips.
c. Place instrument and inner container in a heavy
calton or wooden box and seal with strong tape or metal
bands.
d. Mark shipping container "DELICATE INSTRU-
MENT", FRAGILE'" EtC.
2.22. INTERFACING (Options 002,003 only).
NOTF:
The 3575A Options 002 and 003 are identicol except that
Option 003 instruments use high-true logic for the BCD
outputs. ln qll other respects, the following ittforrnation for
Option 002 instruments also applies to Option 003 instru-
ments.
2-23. The 3575A Option 002 supplies BCD outputs that
correspond with the panet meter readings and is equipped
for remote control of all front panel functions, ranges and
settings (except LINE ON/OFF). The remote input and
output lines are available at the rear panel Interface
connector, A19Jl.
2-24. Fig)te 3-9 (Section III) illustrates the 3575A Option
002 Interface connector as viewed from the rear of the
instrument. The connector drawing and the table within the
figure provides complete input/output and control infor-
mation. A 50-pin mating connector (-hp- l25l-0086*)and
a 46{onductor cable are required to connect all input and
output lines, cicuit Sround and + 5 Vdc to an external
controller or I/O card.
2-25. Computer lnte acing,
2-26. For interfacing the Model 3575A Option 002 to an
-hp- computer, it will be necessary to utilize the informa'
tion in this Inanual to develop I/O circuitry and software
that n)eets individual system requirel]lents. For more
Model 3575A
detailed information concerning the 3575A Option 002,
refer to Paragraph 3-71.
2-27. Printer I nterfacing.+*
2-28. The 3575A Option 002 can be connected directly to
an -hp- printer (Model 50508 or 5055A) using the -hp-
562A-l6C printer cable. The 3575A BCD output and data
flag connections are compatible with the 562A-l6C cable
and modifications to the printer or pdnter cable are not
required. The printer, however, must be set or wired to
accept ground-trus BCD inputs ard an external ground Iead
must be connected between the printer chassis and the
35754 chassis. In addition, there are two minor modifi-
cations that should be performed on the 3575A:
a. The l-ocal/Remote control line (J1 pin 50) is
automatically grounded when the 562A-l6C printer cable is
connected. Grounding the Local/Remote line enables the
timing circuits in the 35754 but also disables the front
panel controls and enables the remote control lines. Besides
being inaccessible with the pdnter cable connected, the
remote control lines (Jl pins 9 through 12,34 through 37)
are connected to the BCD input lines that control unused
printer columns, 5 and 6. If remote contol operation is
desired, it will be necessary to fabdcate an adapter that will
isolate the unused printer-input lines and permit external
connections to the 3575A control lines. If front panel
operation is desired, connect thejumper wire on the 3575A
lnterface Assembly (4168) between points I and 3 (see
Paragraph 3-86).
b. When using a printer it is necessary to supply a
Remote Measure command to the 3575A to initiate the
measurement cycle. When the printer cable is connected to
the 3575A, the Remote Measure line (Jl pin 2l) is not
accessible. For this reason, a test point labeled "TRIG-
CER" is provided on the Intedace Assembly, 4168. The
'lrigger" test point is connected directly to the Remote
Measure line. For convenience, install a female BNC
connector (-hp- 1250-0083) in one of the holes provided on
the rear panel (Item 13, Figure 3-2) and connect a short
piece of wire between the BNC connector and the 'higger"
test point on Al68. Apply the Remote Measure command
to the BNC connector.(Also see Paragraph 3-80)
NOTE
The 562A-16C pinter cable does not prot ide a solid
ground connection bet\t)een the printer and the 3575A. For
this reason, it is necessary to connect an extemal ground
lead (short piece of copp* braid) between the pinter
chassis and the 35754 chassis.
2-29. For further information concerning the use of a
printer with the 35754 Option 002, refer to Paragraph
3-87 .
* Cinch No.57 3050G375
** For Option 003 instruments, the printer must be set or wired to accept high-true BCD inpuls.
2.2

Model 3575A
SECTI
PERATING !
3.1. INTBOD UCTIO N.
l-2. This section contains completc operating instructions
for the Nlodel .1575A Gain"Phase Meter. Included is a
description of controls. general operating information, a
basic operatins procedure ard information concerning
Optior) 001 thrrrueh ()Oi instrunreDts.
3.3. CONTRO LS ANO INDICATORS.
-3-,1. Figurcs -i- I lnd -l'l illuslrate and describe the Iunction
of all front and rear panei controls, connectors and
indicators. The dey:ription ()f eacir item is keyed to the
drawing within the figure.
3.5. GENEBAL OPERATING INFORMATION.
3-6. lnput Connections.
3-7. The input si8nals can be applied to the 3575A through
twisted pairs, shielded cables equipped with BNC connec-
tors (-hp- l050iA ('ablc Asscmbly ), or 10:l divider probes
(hp- 1000.1A Voltagc Divider Probe). Test leads should be
kept as short as possiblc to n)ininize extraneous pickup
and/or loss due to cable capacitancc. When using l0:l
divider prr.)bes. it is first .ecesMrv to compeuate the
probes as outlined in Paragraph 3-62.
3'8. G rou nding and Termination.
3"9. ln the design of the 3575A, extra care has been talen
to control internal gound currents that could degrade the
accuracy of anplitude and phase readilgs. Due to it's wide
dynamic range and high sensitivity, however, the 3575A
can be affocted by external ground currents or "ground
loops" that are caused by poor grounding or incorrect
tennination. This nrcans that when usirg the.l575A,
particularly at low levels and low frequencies. the operator
must be extremely "ground conscious ' if accurate. repeat-
able readings are to be obtained.
3-10. There are basically two types of ground loops that
can cause measurernent errors in the 3575A. The flrst type,
commonly knorvn as a powcr-line ground loop, is encoun-
tered at frequencies trelow the power,line frequency or at
Section UI
0N ilt
NSTRUCTIO NS
integral multiples of the poweriine frequency where either
or both input signals are below 50mV. Il1e power-line
ground loop is caused by extraneous curents that ci0ulate
between the signal source and the 3575A by way of
power-line ground. The other type of ground loop is
introduced by the signal source and is generally encoun'
tered at frequencies below I MIJZ where the signal 3pptied
to one channel is greater than I V nns and the signal
applied to the other channel is less than l0 mV rms. These
two types of ground loops are illustrated in Figures 3--l and
-l-4 and arc discussed in the following paragraphs.
311. Power'Line Ground Loop. Figure 3-3A shows the
hput arrangement for a simple grounded measurement. Ein
represents the source being measured along with any noise
associated with it and is generally called the "nornal"mode
source". Rs represents the source resistance and the
resistance of the high leadl Rg represents the resistance of
the ground lead. Current from Ein (normal-mode current)
flows tluough Rs, Z; ald Rg and the instrument responds
to the drop across 21. As long as the grounds on both sides
of Rg are identical, extraneous currents cannot ciculate
between the source ground and the instrument ggound. If.
howevcr. the grounds are differcnt due to voltage drops in
the ground lead or currents induced into it. a new source is
developed and the measurement appears as shown in Figure
3-38. The new source, Ecm (the dilference between
grounds) is called the "common-mode source" be.cause it is
'comflron to both the high and ground iines. Common'mode
current can flow through Rg or through fu and 21. Since
Zl is usually much larger than Rs and since they are both in
parallcl with Rg, most of the voltage across Rg will appear
acrr.rss Z1 causing an error in the amplitude or phase
reading.
3-12. To mininTe power-line ground loops. the following
guidelines rhould be observed:
a. Keep input leads as short as possible.
b. Provide good ground connections to minimizc the
resistance of Rg.
c. Connect the sigrul source and the 3575A to the same
power bus.
d. lf a removable ground strap is provided on the signal
source, float thc source to brcak thc comnlonrnode current
p3th.
0
-3,1

Section lIl Model 3575 A
STANDARD MOD EL
OPTION 001-003
Figure 3-1. Front Panel Description.
o
o
o
o
o
Pancl Meter (Standard l!4odel 35754): lndicates ampli-
tude or phase d€pendinq on position of DISPLAY switch
(See Paragraphs 3-30 through 3-33).
Left'Hand Panel Meter (Options 00'l-003): lndicates
amptitude only and is controlled by the AMPLITUDE
FUNCTION switch (See Paragraphs 3-32, 3-65 through
3-68).
Rlght-Hand Panel l!4eter (Options 001 003 only): lndi-
cates B dBV or phase depending on position oI AMPLI-
TUDE B/PHASE *vitch (See Paragraphs 3-33, 3'68 and
3-69).
LINE Switch: Applies line voltage to the instrument
when set to the ON position.
DISPLAY Switch (Standard Model 3575A): Selects
AMPLITUDE or PHASE presentation.
Al\4PLITUDE B/PHASE Switch (Options 001-003: Se-
lects ANIPLITUDE B (B dBV) or PHASE presentarion for
the Righl'Hand Panel N4eter.
Channel A Voltage Range Swirch: Selects the input range
for channel A (See Paragraphs 3-24 through 3-26).
FREOUENCY FIANGE Switch: Selects any of four
overlapping frequency ranges. The upper limit within each
range appliEs to phase only. The lower limit applies to
both amplitude and phase (See Para 3"27 through 3'29).
o
@
AIVIPLITUDE FUNCTION Switch (Standard Model
35754): Controls the meter presentation when the DIS'
PLAY switch is in the AMPLITUDE position. The
A|PLITUDE FUNCTION switch selects any oI three
functions: Log A (AdBV), Log B {BdBV} or Log B/A
(dBl.
AIVIPLITUDE FUNCTION Switch (Options
001-403): Controls rhe Left-Hand Panel [,4eter presenta-
tion. As in the Standard Model 3575A, selects Log A
{A dBV}. Los B (B dBV) or Los B/A (dB).
PHASE REFERENCE Switch: controls the phase o{ the
reference channel, Channel A. Wirh the PHASE REFER-
ENCE switch set to the A position. the phase rarding is
direct. With the switch set to the - A position. the channel
A signal is inverted and the phase reading is olIset by 180
degrees (See Paragraphs 3-34 through 3-36).
Channel B Voltage Range Switch: Selects the inpul range
for channel B (See Paragraphs 3-24 through 3-26).
Channel A lnput Connector: Fernale BNC connector
accepts 0.2 mV rms to 20 V rms, 1 Hz to 13 MHz input
signal for channel A. lnput impedance is 'l l,4egohm
(nominal) 30 pF (See Paragraphs 3€ and 3-7).
Channel B lnput Connector: Femle BNC conncctor
accepts o.2 mvrms to 20 vrms, I Hz to 13 MHz input
signal for channel B. lnput impedance is 1 l!4egohm
(nominal) 30 pF (see Paragraphs 3-6 and 3-71.
3-2

Model 35 75A Section III
@
lnterface Connector, A'19J1 (Oprions 002, 003
only): Accepts low-true binary inputs lor remote control
of all front panel functions, ranges and settings. Supplies
8-4-2-1 BCD{oded outputs for the two panel meters (See
Paragraphs 3'71 through 3'74).
Holes: Provided for installingr€r p6nel input connectors
in place of the front panel connectors.
Ground Terminal: Connected to circuit ground and ouler
chassis ground. Terminal permits connection to chassis o,
signal source or to other external ground to help minimize
ground loops {See Paragraph 3-17).
ANALOG OUIPUT 2 (Oprions 001-003 only): Supplies
dc voltage (10 mV/dBV or 10 mv/deg.) that corresponds
Figure 3-2. Rear Panel Oescription,
with the Righr-Hand Pan"l Meter reading (See Paragraphs
3-37 through 3-40).
ANALOG OUTPUT 1 (Standard N4odel 35754): Supplies
dc voltage (10 mV/dB or 10 mv/deqree) that corresponds
with the panel meter reading. (See Paragraphs 3-37 and
338).
ANALOG OUTPUT 1 (Options 0O1-{03): Supplies dc
voltage (10mV/dB) that corresponds with Left-Hand
Panel Meter reading (See Paragraphs 3-37 through 3-40).
Power lnpur N4odu,e (A'l8l: Accepts power cord supplied
\,!ith the instrument. Contains line fuse and 1 15 V/230 V
selector switch (See Figure 3-5).
R.
HIGH SOURCE
R ES LSTAN CE
GROUNDED
I\4EASURING INSTRUIVENT GROUNDED
MEASURING lNSTRUIVENT
R9
GROUND LEAD
RESiSTANCE L
c0rv Nl0N
IVOOE
SOURCE
B
IN STRU IV EN T
GROUND
A
HrGHI
I
Figure 3-3. Power-Line Ground Loop.
3-3

Section lll
3-13. Source-induced Ground Loop. Figure 3-4 i.llustrates
a ground loop that is introduced by tllc signal source. [n
Figurc 3-1, the signal applicd to channel A is I V nns and
the siSnal applied to channel B is 0.1 mV rlns. As illustrated
h the figure, part of thc currcnt from the 2 V source
returns through the ground lead of the 0.2 mV source
producing a voltage drop across the ground lead resistance,
Rg. As in the power-line ground loop, the source resistance,
Rs and the ground lcad resistance Rg are in parallel with
Zb. Due to thc 50 olun terminatior place directly across
Zb. howeycr. less than half of the voltage dropped across
Rg is present across Zb. Although this voltage is very small,
it is largc crlough to affeot thc amplitude and/or phase of
the 0.1 rnV signal.
-l-14. Note that r)rost (,f the currert from the 2 V source is
flowing through the 50 ohm tennination of the channel A
input and depending on the rcsistance betwcen the A and B
input conl lons, a good portion of the current is returning
through thc chanuel B ground lcad. lf the 50 ohm
ternrination was placcd directly across the output of the
2 V source, howevcr, very little current would flow in the
ground leads. Lowering the current in the ground leads
rc,lu;c: tlrc tlrop rcross \ :rnrJ thercbl rninirDi/cs llre
c()rrtlnon- lodc voltage and llre resullinS cIlor.
l-15. Fortunately, this type of ground loop is predomirate
at low lrequencies (below I MHz) where it is possible to
tenrinate at the signal source rather than at the input of
the nreasuring instrunrent. At high frequencies where it is
nocessrry to terminate at the end of the transmission line,
the error is normally insignificant asir.lngas shielded cables
or twisted pairs are used for the input connections.
3-16. To midmize ground ourrents introduced by the
signal source. observe the following quidelines:
a. At frequencies below I MHz, place the termination
for the high-level signal directly across the output of the
highJevel signal source.
l) At frequencies above I MHz. tenninate at the
3575 A input.
b. lf ternination for the low-level signal is required,
place the termination at the input of the 3575A.
c. Provide good ground connections by using strielded
cables equipped with BNC connectors. If shielded cables are
not aYailable, use twisted leads.
d. Keep rnput cables and leads as short as possible.
3-17. Checking For Ground Loops. To check for prwer-
linc ground loops. proceed as follorvs:
a. Apply a 0.1 mV to 50 nrv rms. I [Iz to 60 Hz (or
other powcr-line frequency) signal to either or both of the
3575 A inputs.
34
Model 3575 A
Figure 34. Source-lnduced Ground Loop.
b. Set thc 3575A to rneasure the amplitude ol the
applied signal and note the panel meter reading.
c. Connect a short piecc of copper braid bctween rhe
conunon terminal of the sigrul source and the 3575A input
common (on one of the BNC input connectors).
d. A.uow time for the instrument to stabilize and acain
note the panel meter reading.
e. If connecting the copper braid has produced a
significant change (t 0.5 dB) in the reading, a ground loop
is present and corrective action (Paragraph 3-12) shouid be
tatr en.
NOTII
A gnrund tenllinol (ltent 11, Fipra 3-2)is proyidetl ort tltt'
J57-5A rear pancl to parnit axtanwl gruualing. In tast,s
wlrcrc grourtd knps arc LritiLal attd dilliL\tlt Io cr tol, it i\
sotltatinrcs bctteficial to qD|tc('t q sht)rt piecc ol cLtytptr
braid ltetwcc'rt tltis grolutd tcrttitul akl tltc cltossis o.l tltc
signol sourcc. 1"0(tur.t' tests ltoya in.licotctl, ho\r'crcr, tltat
tllc lc gtlt and positio ing ol tlrc u)ppcr braid L'an hc
rritical. Bj,,ri rttittg tltis lc.-lutitluc itt ,t tttoyrrttttittt
appli('dtio , exparifirc t ttitlt vorioLts gruutul poi ts, lcaLl
latlgths arul l€sd pt,sitio s to cstoblislt a gnwncliug rttctltLtl
llwt e surcs ouuratc, repcatahl( rcaLlittgs in .t'ut porticular
sitLtatiolt-
3-18. To check for source induced ground loops. proceed
as follows:
a. Apply a I V to l0 Vnus. l0 Hz to l0 kllz sigrul to
one channcl and u 0.1 mV to l0 nlv nns sienal to the other
cha nnel
b. Set the -1575A to rneasurc tlle xmplitudc of the lorv
level signal and llotc ths panel meter reading.
c. Disconnect the higl) levcl signal lrorrr lllc 3575A.
50n MEASL]R NG N STRUM ENT
2V
M ODE
O.2 mV
MOOE
souRcE PEOA\'E
R!
s0n
)[l 50 oirM a
6N0
R9 GND
)l
50 oHrv l, -la
9l v

Model 1575A
d. A.llow time for thc instrumert to stabil2e and again
note the low level anrplitude reading.
e. If disconnecting the high level signal ltas produced a
significant change (1 0.5 dB) in the bw level reading, a
ground loop is present and corrective action (Paragraph
3-l(r) should bc taken.
3-19. lnpul Constrainls.
3-10. The E0dB dynamic range of the 3575A provides
wide freedonr lion) input constraints. In rnauy cases. it will
be possible to nral(c all the necessary mcasurcments without
changing voltage ranges. It is irnportant. howcver. to
obscrve the nr&\irnunr input levcls (l V rrns or l0 V rms)
indjcated b! lhe Voltage Range settirlg. Exceedilg tliese
input levels rvill causc the display to blank. thc overload
indicator (AOL or 861) to illullliDatc alld car datnage thc
instrurllcnt if the applied voltage is greater than l5 V rms or
50 V dc.
3-21. DC lsolation.
3-::. Thc -1575.\ inputs are cquippcd with coupling
capacitors to pr()\'ide dc isolation. The maxinunr dc voltage
that ca be :afeLy applied Lo the inputs is i 50 Vdc.
Excceding lhis lirnit can cause breakdown of the input
capacitors rL'sulting in ddnragc to the ilput arnplifier
circuitr!.
3-1.1. fhc -i575-{ ca not be operated in a floating con-
ditioo. All IupLrt ard Output conrmons are connected
dire.tl) to outer chassis (iiame) gound which connects to
earth ground rluough the offset pin on the powcr cord
connector.
3-24. Voltaqe Banges.
3-15. E3ch input channel is equipped with a range switch
which pennits selzution of two overlapping voltage ranges.
lnput voltage Iirnits rvithin each ralge are as follows:
0.1 rnv rrns (- 74 dBV) to I V mrs (+ 6 dBV)
I mV rnrs t 5.1 dBV) to l0 V nns (+ 26 dIJV)
3-26. As long as the applied sigul is within the lirnits ol
both ranges (2 mV to I V), either range settiirg can be used.
Changing the voltage range settilB does not alfect the
display resolution- For optimum accuracy. however. it is
recomnrended that the 0.: nrV to I V ran8e by used at all
tirnes uniess the applied sigoai is greater than I V rms. The
reason ior this is that on the I mV 1o l0 V ralgc the input
signal is divided by the l0 dB inpul atteirullor. Any noise
tlut is gcnerxted withir the 15754. however. is not
attenuated and the sigrul to noisc ratio is decrcased.
Decreasing thc sigml lo noise ratio rnakes thc instrunrertl
nrorc suseptable to noise which can affect tl)e accuracy of
amplitudc and phase rcadings. It should bc noted that the
Phase Accuracy spocificrtions (Tabie l-l) are nret only'
when the lowest applicable voltage range scttings arc Llsed.
Section III
3-27. Frequency Ranges.
-l-18. The broadband frequencl response of the -]575A
extcnds from l tlz to 13 MHz in four overlapping ranges.
frequency limjts within each range are as foUows:
lHztolkHz
I 0 Hz to 100 kHz
100 tlz to I Nltlz
I kHz to 13 IlHz
3-29. The FRIQUENCY RANGE setting determines thc
amount ol filtering that is used throughout thc iustruntent.
The filtering, in turn, controls the frequency response and
overall settling time (See Tablc 3-l). The frequcncy ranges
are designed such that the lower limit ol each range applies
to both amplitude and phase and the upper lirnit applics
or y to phase. For exarrplc, it is possible to use the 1 FL to
I kHz rangc for al anplitutlc mcasurcments witllirl the
liequency range of I Hz to l3 NlfL. For most arnplitudc
measuremcnts, however, it is best to use one of the upper
rarlges k) minimize settlin8 tiine. The main thing to
remember when making amplitudo n)easurenlents is that
the frequency of the input signal(s) must be above the
lower limit of the selected frequency range. Vhen mea-
s.rring phase. it is necessary to observe both the upper and
Iower limits of each freque|cy range. The Lrppcr linlits.
which apply to phase only. are dctennined by noise filters
which control the high frequency cutoff characteristics of
the phase detector circuits. For optimurn phase accuracy. it
is nocessary to use the frequency range that provides the
greatest noise immunity ar./ the required bandpass. This
means that the 1r)i1'.,J1 range Lhat covers the frequency of
the input signals must be used. It should be Doted that the
Phase Accuracy specifications (Table 1-l) are rnet only on
the Iowest applicable frequency range.
Table 3-1. Typical Settling Time.
(Iollowinq a change in input parameters)
100%*
settled 95%*
Settl€d 90%"
Setrled
1 Hz'1 kHz
10 Hz-lO0 kHz
100 Hz 'l MHz
l kHz . l3 MHz
30 sec.
3 sec.
0.3 sec.
30 ms
20 sec.
2 sec
0.2 sec.
20 ms
17 sec.
0.1 7 sec.
17 ms.
- Percent of finrl reading.
3-30. Meter lndication.
.l-31. nre -1575A panel nleter indicates direotly in dB or
dBV for anlplitude nreasurenrents and in degrees for phase
rleasurenler)ls. The iront panei DISPLAY stvitch penlits
sclcctiorl of cithcr ANIPLITUt)E or PHASE prcscltatiorr.
3-32. Amplitude Presentation. With thc DISI'LAY sritch
ir, tlre L\IPLlltLrl p,,.ili,,I. IIrc rr.lcr l,re,er,rJIr'.. r'
deternrined hy lhe ANIPLITtiDI: FtINCTIO\ control
sctting. -llle tlrr.e irnplitude iilllctio s :rrc: Log A. Log B
Li

Section Ill
and Log B/4. When A or B is selected, the panel meter
irdicates the anlplitude of the correspotding inpul signal in
dBV (l Vrrns=0dBV). The overall mcasurement range for
the Log A and [.og ts an]piitude lunctions is from - 74 dBV
(0.1 nrV rns) to + 16 dBV (J0 V nns) providing a total of
100 dB in two voltage ranges. The 3575A alnplitude
readings are displayed with 0.1 dBV resolution over the
cntire Ineasurenrent range. \\4ren ll/A is selected, the 3575A
nleasures the relative amplitude of (differcnce bctwecll) the
two ilput sigrlals in dB. The disptav range for relative
rneasurerrents is from - 100 dB to + 100 dB with 0.1 dB
resoiutior. Relative arnplitude readings are displayed with
respe[t lo clunnel A which is the rcference channel. A
ncgative reading indicates that the signal applied to charnel
B is /orler in amplitude tlun the signal applied to channel
A. A positive reading indicates that the signal applied to
channel B is greater i\ amplitude than the sigral applied to
channel A.
333. Phase Presentation. With the DISPLAY switch in the
PHASE position, the panel rneter indicates the phase
difference between the two input signals in degrees. The
display range for phase measurenents is from - 192 degrees
to + l9l degrees with 0.1 degree resolution. The r 192
degree limits provide a t ll degree oyerrange capability
which eliminates alnbiguous readings in the t 180 degree
region.
3-34. Phase Reference. The 3575A phase readings are
dirylayol with respect to channel A which is the rclerence
r:hannel. A negative pluse reading indicates that ts lagsAi
x positive phase reading means lhat B leads A.
3'35. With the PHASE REFERENCII switch in the + A
position. the panel meter indicates the actual phase
difference between the two input signals. With the PIIASE
REFERENCE switch in the - A position, channel A is
inverted and the phase reading is offset by 180 degrees. For
example, with a phase difference of +60 degrees (B leads
A) apptied to the inputs and the PHASE REFtr,RllNCli
switch set to the + A position. thc pancl metcr will indicate
+60 degrees. lf the PHASE REFERENCE switch is
changed to the - A position. ohannel A will be inverted and
the panel rneter will indicate - 120 degrees.
3-36. Uccause of thc 1 ll degree overrange capability, thc
3575A never gives alnbiguous phase readings. This means
lhat it is not necessary to change the phase reference for
measurements in the t 180 degree rggion. fhe ability to
charge the phase refercnce is strictly a convenience fcaturc
rvhich is uscful for some measurernent applications. One
exarnple of this is where it is neccssary to make a
continuous phase vs. lrequency plot over 360 degrees of
range. Consider the case where two signals are initirlly in
phase and as lrequency is varied 1he phasc diffcrence
increases in a positive direction. With the ph-ase reference
set to + A, the plot starts out at 0 degrees and increases
with frcquency until the phase difference reaches approxi-
mately + 192 degrees. At this time, the 35754 reading
automatically jurnps to " 168 degrccs and again goes more
positivc with frcquency. 'fhe result is a discontinuous plot.
-l-6
Model 3 575A
By initialy setting the phase reference to - A, howcyer, a
continuous plot could be obtained. The plot would start
out at - 180 dcgrees and continue in a positiye di.rection
through + 192 degrees extending the continuous range by
180 degrees.
3-37. Analog 0utputs.
3-38. Two BNC connectors, labelcd ANALOC OUTPUT I
and ANALOG OUTPUT 2, are located on the rear panel of
the instrument. On the standard Model 3575A, ANALOG
OUTPUT 2 is not used. The remaining connector, ANA-
LOG OUTPUT 1, is connected through a I kilotun resistor
to the aDalog (dc) voltage applied to the panel nleter. Since
this voltage is not affected by errors within the panel meter.
it is more accurate than the panel meter reading. For tliis
reason, the amplitude and phase accuracy specificatiorls
listed in Table 1-l apply to the analog output and do nor
rcflect the :t 3 count panel meter tolerance. The arulog
output voltage is delined in the accuracy specifications as
l0 InV per degree for phase measuremelrts and l0 mV per
dB/dBV lor amplitude measurements (with >2 Nlegohnl
load resistance). In the Amplitude Display mode, the aiulog
output voltage ranges from " I Vdc ( 100 dB) to + I Vdc
(+ 100 dB). ln the Phase Display mode the voltagc ranges
from - l.9l Vdc (- 192 degrees) to r l.9l Vdc (+ l9l
dcgrees). The analog output resistance is I Kilohrn and
short-circuit protection is provided. To obtain an output of
l0mV per degree or l0mV per dB/dBV, the load
resistance connected to the analog output must be
2 Megohrn or greater. Additional loading will not damage
the i|strunent or degrade the linearity but it will reduce
the output voltage by an amount proportional to tlte load
resistance.
3-39. Dual Analog Outputs (Options 001 through 003).
-l-.10. For instruntents equipped with dual panel nreters.
ANALOC OUTPUT I is connected to ihc left,hand (facinc
the lront panel) panel meter (allrflitude) and ANALOG
OUTI'LJT I is connected to thc righrhand panel meter
(plt.rse). The anaiog output nrltagcs correspond with rhe
respeclive panel nleler readings and can be used fnr
sirnL taneous amplitudc and phase plotting. For further
infbr rution conccrning Options 001 00-1. refer to Para-
graph 3-6,1.
3,41. BASIC OPEBATING PROCEDUHE.
3-42. lnstrument Turn 0n.
a. Rcfer to Figure 3-5 and perform the following:
l) Remove the fuse and set the line selector switch
to correspond with thc line voltage to be used (l15 V or
230 V).
2) Replace the fuse using a 0.64, 250 V slo-blo for
l15 V operation or a 0.3A, 250 V slo-blo for 230V
operation.

Model 3575A Scction III
3575A, the instrument will rcspond to extraneous pickup
and residual noise. For this rcason, the displa) ma)' not
stabiiize until inputs are applied.
3-43. Am plitude Measurements.
?44. Log A and Log B Measurements. The single channel
anplitude lunctions A or IJ. permit direct nleasureinent of
either input level in dBV. These readings can be converted
to ac volts using the graph shown in Figurc 3-(r. To measure
the level applied to either input channel. proceed as
follows:
a. Set the DISPLAY switch to the AMPLITUDE posi-
tion.
b. Set the {\{PLITUDE FUNCTION switch to A or
depending on rvhich input is to be measured.
c. Set the Voltage Rangc and FITEQUEN'CY RANGE
switcher to appropriate settings as outlined iu Paragraphs
.l-2zl and -1-17.
1.
2_
3.
5.
POWE R CORD RECEPTACLE (A18P1}
FUSE COMPA RTMENT COVE B
]]5 V1230 V SELECTOR SWITCH (A18S1)
F USE PU LLE R
LINE FUSE (A18F1), 0.6A,250V SLOBLO
OPERATION)
0,3 A, 25O V SLO-BLO
OPE RAIION )
(11sV
(230 V
a. DISCONNECT POWER CORD AND SLIDE THE COVER
TO THE LEFT TO GA1N ACCESS TO THE FUSE COM
PARTMENT,
b, RE[,4OVE THE LINE FUSE BY PULLING OUTWARD
ON THE FUSE PULLER,
c. WITH THE FUSE PULLEB POSITIONEO AS SHOWN.
SET THE 1]5V/230V SELECTOR SWITCH TO THE
POSITION THAT CORRESPONDS WITH THE LIN E VOLT.
AGE TO BE USE D.
d, REPLACE THE LINE FUSE USING A 0.6A, 25OV
SLO.BLO FOR 115V OPERATTON OR A 0.3A, 25OV
SLO.BLO FOR 23O V OPERATION
Figure 3-5. Power lnput l\4odule A. B and C.
b. Connect the detachable ac power cord to the rear
panel power receptacle ard to the power source (l l5 Vor
230 V, 48 HZ to 44O Hz).
c. Set the LINE switch to the ON position. The panel
meter display w l illuminate. With no inputs applied to the
Apply sigral to the appropriatc input channel
A]low tirne tbr the readinS to stabilirc.
f. Observe the alnplitude reading in dBV.
g. II desired, convert the d BV read,ng to rnrs volts using
the graph shown in Figurc -l-6.
3-45. Relative Measurements (Log B/A). In the B/A ampl-
tude function. the 3575A measures the relativc amplitude
of the two input signals in dB. Tlris iunction is particularly
useful for measuring gain. attenuatiorl nnl frecluency
response. The use oI siinultaneous conrparisor) elinri|ates
the need for separate input and output measurcmcnts and
provides relative readings thrt are independent of source
variatioIls.
3-46. Because the two input channels are totally indcpen-
dent. relativc nlcasurcrrents can be madc between two
signals that dilier in tiequcrtcy. It should be noted,
however, that both input iiequencies rnust be dlr.n (, the
lower limit of the selected frequency rarge (see Paragraph
3-.17. For relative measurements using thc B/A function.
proceed as lirllows:
a. Se1 the DISPI.AY switcli to tl're ANIPLITUDE posi-
tion.
b. Set the A,\IPLITUDE f UNCI ION switch to B,/.\.
c. Set the Voltage Ilarrge and FREQUENCY RANCE
switches as outlined in Paragraphs -l-:.1. -l-17 anLl -1J6.
d.
l-'1

Section III
d. Remembering tnat channel A is tile reference
channel, connect the signals to be mea$.rred to the 3575A
Input colnectors.
e. Allow time for the reading to stabilize.
f. Observe the relative amplitude reading in dB. A
negatiye reading indicates that B is lower than A;a positive
reading means that B is geater than A.
g. When making relative measurements ensrre that the
input levels are within the limits of the voltage range
settings being used.
3-48. Phase Measrements
349. With the DISPLAY switch in the PHASE position,
the 35754 measures the phase difference between the two
input signals in degrees. To measure phase, proceed as
follows:
a. Set the DISPLAY switch to the PHASE position.
b. Set the PHASE REFERENCE switch to + A or as
outlined in Paragraph 3-34.
c. Set the Voltage Range and FREQUENCY RANGE
switches as outlined inPangrapts 3-24 and 3.27 .
d. Connect the signals to be measured to the 35754
Input connectors.
3-8
Model 3575 A
e. Allow time for the reading to stabflize.
f. Obsewe the phase reading. Since A is the reference
channel, a negatiye reading indicates that B lags A; a
positive reading indicates that B leads A,
3-50. Effects of Harmonic Distortion on Phase Read-
ings. In the 3575A, phase difference is measured between
the zero crossing points of the applied signals. If an applied
signal contains harmonics of the fundamental frequency,
the zero crossings may be shifted with respect to a pure sine
wave. If the instrument responds to the false crossings
introduced by the distortion, an eroneous offset will
appear in tlle phase reading.
3-51. The amount of enor introduced by harmonic
distortion depends on the magnitude, phase and order of
the harmonics. Harmonics that are in phase with the
fundamental (such as in a square wave) do not cbange the
zelo crossing points and do not affect the phase readi€. In
the 35754, the effects of even harmonics are cancelled b1
two phase detecton that operate 180 degrees out ofphase.
For this reason, wen harmonics, regardless of their phase,
do not affect the phase reading. This leaves only odd
harmonics that are out of phase with the fundamental.
3-52. The amount of eror introduced by odd harmoaic
distortion again depends on the magnitude and phase of the
harmonics. The largest error occurs when the odd harmon-
bs are 90 degrees out of phase with the fundamental. In
Figure 3-6. dBV to Volts Conve6ion.