A D A 0?4 409 TEXAS LRIIV AT AUSTIN APPLIED RESEARCH LABS n e insEVALUATION OF THE AN/SQS—23 TR—208A TRANSDUCER (SERIAL BTD 2—69 CTC(U)DEC 69 .1 0 TRUCHARD. D 0 BAKER N0002* 69 uCeiO66

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ARL.TM.69-35 Copy No. ~?23 December 1969

EVALUAT ION OF THE AN/SQS.23 TR.208A TRANSDUCER (SERIAL BTD.2-69)

NAVAL SHIP SYSTEMS COMMANDD. D. Bak.r Cont rac t N00024.69.C.1Ob6J. .1. Truchord A Proj Sir . No. SF 1fl21300. Tas k 08048

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IA RL-TM.69.35 23 December 1969

EVALUATION OF THE AN/SOS.23 TR.208A TRANSDUCER (SERIAL BTD.2.69)

D. D. BakerJ i. Trucba,d

NAVAL SHIP SYST EMS COMMAND~Contr act N00024 .69-C.I066/Proj. Sir. No, SF 11121300 , Tas k08048

A P P L I E D R E S E A R C H L A B O R A T O R I E ST H E U N I V E R S I T Y OF T E X A S A T A U S T I N

• AUST1PI, TBXAS 78712

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ABSTRAC T

Applied Research Laboratories evaluated the AN/ SQ~ _23 TR-208Atransducer (serial BD- . -t~9) by measurements at the Lake TravisTest Station in April 1969 and by shipboard measurements inSeptember 1969. The principal measurements made were compleximpedance (z and 0) of individual transducer elements, drivenindividually at operating power. A conclusion drawn from thiswork is that impedance data measured on the bare transducerin open water compare (to within measurement accuracy) withthe shipboard measurements made in the dome . This is a highl yfavorable indication and is a further incentive for the wide-

• spread use of element impedance measurements for transducerevaluation. In the past , such measurements have proved to bevery effective at diagnosing transducer failures and impendingfailures.

NT1S~~~~~~ID~~ TABUn~mnouncedJustific~ition ________

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ILTABLE OF CONTENTS

Page

ABSTRAC T iii

I. INTRODUCTION I

II. BACKGROUND 3III. A.BL TEST PROC EDURE 5

A. Tests Aboard ARL’s STEP Bar ge 5B. Shipboard Tests 6

IV. ABL TEST RESULTS 9A. Bare Transducer Measurements 9B. Measurements in the Dome 12

C. Shipboard Measurements l~V. COMPARISON OF RESULTS WITh PREVIOUS TESTS AT T}~ 17

BOST ON TPFVI. SUMMARY AND CONCLUSIONS 19

A. Baseline Measurements 19

B. Shipboard Impedance Measi~irements 21

I-

5:~~~~~~~~~~~~~~~~

I. INTRODUCTION

Applied Research Laboratories conducted an evaluat ion of theAN/SQ~-23 TR-2O8A transducer (serial BTD-2-69) at the Lake Travis

Test Station (LTTS) during April 1969. This transducer was shipped

to ARL at the request of Naval Ship Systems Coimriand (NAVSHIPS) from

the Transducer Repair Facility (TRF) at Boston Naval Shipyard. In

May the transducer was reshipped to Boston where it was subsequently

installed aboard the USS VOGELGESANG (DD 862). ARL personnel repeated

measurements on this transducer aboard ship in September 1969. This

• teehnical memoranthnn contains the results of both sets of measure-

ments on this particular transducer. ARL’s data are also compare dwith data measured at the Boston TPF prior to shipment of the trans-

ducer to ARL. The data from Boston were forwarded to ARL at NAVSHIPS

request (NAVSHIPS letter OOV3M:HCE:sl, 967k, Ser: 52, dated ~~ Decem-

ber 1969) and were received on 15 December 1969.

______________________ — -.---—— —--. ~~~~~c___&_~ -.... .~~~~~~~~~—__ —.—-— — — - — . , . ..~~~ . . , . . - .

— - — 5--- - - - - — --

II. BACKGROUN D

NAVSHIPS has provided ARL a well-equipped barge to serve as a

pilot facility for the Navy’s three TRF’s. Each of the TEF ’ s has

transducer test facilities equipped with the AN/FQM- 1O(V) Sonar Test

Set , as is ARL ’ s STEP barge (nickn amed for Standardized Transducer

Evaluation Program) .

One of the uses envisioned for the STEP barge was that new types

of transducers would be sent to ARL so that baseline measurement s

could be obtained. From these measurement s ARL would be able to recom-

mend meaningful tests for the TRF ’ s to use on the transducer and to

provide reasonable test parameters and tolerances.

The first transducer sent to ARL for baseline measurements was

the TR-208A, serial BTD-2-69 . It did not represent exactly the “new

transducer” case because the TR-208A is merely a relatively new design

of an existing type of transducer, for which the TBF ’ s already have

meaningful test requirements. Test tolerances have been established

but not thoroughly checked.

ARL ’ s first objective was to make the “TRF measurements” on the

bare transducer to verify existing tolerances or suggest changes in

them. These data would also be compared with previous data from the

Boston TBF . The second objective was to establish the validity of

shipboard single-element impedance measurements by investigating the

correlation between such measurements made on the bare transducer and

made on the transducer installed in the standard hull-mount dome . The

STEP barge Is equipped with a standard 360 in. AN/SQ~ -23 dome .

3 _ _

~~ QL~JG p~~-: ~~~~~~~~~~~~~~~~~~~~~ -~~~~~~~

- :-

- - ---—-—- - -- --5-—- —--——~~~~--

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5 - 5 -

It was requested by NAVSHIPS that ARL personnel follow this

• particular transducer and repeat single-element impedance measure-

ments after its installation aboard ship . The purpose of these

measurements was to investigate the comparison between shipboard

measurements and measurement s made in ARL ’s dome at LTTS, as well asto affirm that the transducer was correctly installed. It is planned

that ARL will continue to make similar measurements on thi s transducerperiodically--perhaps each six to twelve months. This procedure ofevaluating a new (or relatively new) type of transducer at ARL andthen monitoring its performance during its life cycle is one thathopefully will be followed on all types of new transducers in thefuture . This cradle-to-grave transducer monitoring will enable

NAVSHIPS to maintain realistic test tolerances on transducers (bothfor the TRF ’s and for shipboard measurements), as well as to monitortransducer performance for the onset of any aging effects or possiblefai lure modes.

- - - - -— -

~~~~~~~~~ — -

-—- —-— - - - • - -.5-- --

III. ARL TEST PROC E~ JRE

A. Tests Aboard ARL ’s STEP Barge

A.RL received the TR-20 8A, serial BTD- -69 , on 9 April l969~ ithad tc~ be received back at the Boston TRF by 15 May 1969 . Afterallowing time for uncr ating/ crating, loading/offloading, conne - ing,

disconnecting cables, and reshipment to Boston, the actual test period

was J April through 5 May 1969.

The test plan for the bare transducer may be simimarized as

fellows:

1. Each of the 1432 elements was driven individually, with a

5 kBz 100 V signal ; its impedance and source level were

measured.

2 . Each of the l~8 staves of the transducer was driven m di-

vidually (with the element s in parallel), with a 5 kHz 100 V

signal ; the source level of the stave was measured. In

this same driving configurat ion, spot checks of the impedance

of the individual elements were made .

Item 1 represents the TRF tests on thi s type of transducer . Item 2

was done to investigate how element impedance shifted as t.he driving

configuration changed and to obtain an additional check of source

level uniformity.

S

-— -5-••~~5-~-~ •~~~~~_ ~~~~~~~~~~~~~~~~~~~~ - - ~~••

~5-•~~~~ --!-w-r ’5~~~~~~

With the transducer in the 360 in. dome, the following test~:were perfonried :

3. Individual element impedance measurements were conducted

exactly as in item 1; however , no source level measurement swere made .

14 Each stave was driven as in item 2 and its source levelmeasured; no impedance measurement s were made .

The tests of item 3 were for the previously stated purpose of

investigating correlation between individual element impedance meas-

urements with and without the dome. Tests of item 14 were done primarily

to compare with the similar source level measurements done in item 2

to see what dome effects existed .

The AN/FQM-lO(V) Sonar Test Set was used for all measurement sat ARL . A block diagram for the exact setup used in the individualelement impedance measurements is shown in Fig. 1(a).

The accuracy of impedance magnitude (z ) measurement s with thePulse Vector Immittance Meter (Scientif ic-Atlanta Model 1700) is ±2 ~2 .Its accuracy for impedance phase (0) measurement s is ±2 deg.

B. Shipboard Tests

Tests on the TR-20 8A, serial BTD-2-69, were conducted aboard

the USS VOGELGESANG (DD 862) on 214 - 25 September 1969. The tests

consisted of only single element impedance measurements , with eachelement driven individually with a 5 kHz 100 V signal provided byan external power amplifier ( not the shipboard sonar equipment).ARL personnel were greatly assisted by a shipyard mechanic familiarwith the installation , who disconnected and reconnected the trans-ducer leads. The short time available was dictated by the ship ’s

schedule for sea trials.

6

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ — --_ - - _ _ _ _ _

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PULSE432 SINGLE VECTORELEMENTS ELEMENT IMMITTAN CESCANNER M E T E R

FIGURE 1(o)MEASUREMENT SYSTEM USING AN/FQM ~O(V) AT LAKE TRAV IS

EAToR~~~~~~~~~~

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F,ER

FIGURE 1(b)MEASUREMENT SYSTEM USED ABOARD USS VOGELGESANG

ARL . UTAS-69 . 129~• JJT . RFO

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The block diagram for the test instruments used for the sl~ipbuai - imeasurements is shown i~ Fig. 1 ( b ) . t\ 1)r ~u iet:- m~del _

~ 7 samplingvoltmeter was used to measure the voltage and ~‘ui - r - ; amp l itu i e s . Adual channel Tektronix type 5614 storage oscilloscope was used tomeasure phase . The external power source f’r driving individual ele-ments was an ARL-built portable s~ 1id state amplifier. The accuracy

~-f this shipboard instrumentation was ± ~2 for Z and ± ~ deg for ~~~.

8

-_ _ _ _

- -

-

- -.5-5-—-,

I

IV . ARL T~- : T h~~1 IT:

A. Pai-e Tran sducer ~easur em ent~

The published speoif icatic-ns Ic r the T~’— : 3~ A that are ap~ 1 Icafle

~o the TAL~~s are taken from ~AVS ’dlP~ publication 9E 7-~ C~ -~~3~ J . The

inz~e-ianoe magnitude of an element ‘it 200 W c n er a t i n c power at 5 kHz

is spes~ fied to be between ~~~ -rid 53 fl; the ~-hase shcu~d r~ ’ige fro ~.-

~~~~~ deg to +15 de~ at the same driving level. Single element s -urce

level should be 97.5 ±1.0 dB re 1 ~bar at 1 yd.

The results of ARL ’ s single element impeWtnce measurements

(each element driven individually) on the bare transducer at L1~S

are shown in Fig. 2. It can be seen that all elements met the phase

specification ; however , 35 element s lay outside the acceptable S r~u~~e.

All but one of these Lay in the range 5~ - 58 ~~~. These out-of- t- — e~-ance

element s represent ~ of the transducer.

As statei in ecticn III, each element was driven individua~~ y

w i t h a l2~ V sign a~ , not at precisely 200 W as the source level

speci f isa t ic:’. sa ’,ls for. The actual driving power levels varied from

~(‘: to 222 V , a range of approximately 1.3 ii~. Based upon these

driving levels, corrections were made to measured source level values

to simulate the 200 W drive level. After these corrections were

made, there remained 814 elements that did not fall within the

96.5 - 98.5 dB range; however, onl y 5 of the:e fell below ~~~~ dF.

9

- ~~~~~~~~ ---~~~~~ - -5- - - - - - —~~~~~~~~~~ ‘ ~~~- - _‘ —.5——- -—~~~~~-— -~~

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90

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70

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~~50

20

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040I

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10

• 00 .5 .10 .15 ARL . UT

•— d . AS.69.1292a JJ T . RFO12. IS. 69

FIGURE 2HISTOGRAMS OF Z AND

~ OF BARE TRANSD UCER AT 5.0 kIli

10

‘5- — -

~ -~~~

5-~~~~

’ 5 -~~~~~~~~~~~~~-- -

r

The mean value of the uncorrected asured oni’~’e level val i ies was

• ~ dP ; ‘by making a ~~~ rio ci ion to ~~~ mipon sat e for the average drivingpower of’ I ~~‘) W , t in ’ correct e~t mean source 1 evi l w:n ~h . ( ‘ dB, a

p ass ing value .

it C~Ui be noted from i ’i g . 2 t hat I lie spread ci ’ S and ~ values

was net great , a very fave r :ti’i e charad e ri st I c for :~~~‘ii a I i’an s1u ~’e r

as ray . Likewi so , even the uj i~’orrect e~t scu rce l evel value s variedon I y t ’ i’en ii i . ~ d]~ t o O (. ~~

Wh en staves of ’ I in t i-an sdu -er wer e Iriven , source level again

was u i t e uniform l ’or I he t ran s Pices n r r : i y . Val iies ci’ stave source

I eve 1 ( for wli i cii t h e re was no mean s of corn ‘ct ing each stave

i dentical 1.y the caine (lniv~ ng power) varied o n l y from 11 ‘.0 t~~ 11 1 4

Of these values , ~~ of the ~~ l a y ‘between 1114.0 and ll ’ ..~ dB; I Iii

mean value of stav e so’~rce level was ii 14. ~ ~~

The spot checks of element impedance measured while staves of’

the transducer (.) elements) were driven revealed signi f icant shi i l’l

in complex impedance of a given element between i-li e condition of it -

being driven alone versus being driven in parallel with i t s no ighi r. .This e f fect , due to element interaction, has been post u I al-ed and

“bce rved man y t. i nec previous y . On this particular frau sducer I Iii ’

shift both in 7 and in ~ is demonstrated by the t yp i cal values shown

in Table I . It can readily be appreciated that ciii t’t-s in S of’ t h eorde r of ~ 0 could cause one to reject good ci emeni;s i t ’ one mcn snr’d

element impedance while driving an entire stave . The value s ci’

Table I certainly indi cate t hat- two set s of element impedance fat a

are not equivalent and thus cannot be compared unless the drivingconi ’i gura t.~ ons are equivalent.

11

--

TABLE I

EL 1~2’11~NT WJMBFiR SHIFT IN Z SHIN’ IN ~

1 ( TOP) -0.7 0 -9 deg

2’ —4.7 0 -1” deg

— .6 1’? — 16 deg

0 -16 deg

._3.9 0 — 16 deg

—14.o 1? — 1 ’- ~teg

1 -3.5 11 -16 deg

8 — ‘ ‘ .7 0 — 1 ’ deg

( Borro~i) -u.8 o -8 j~-

~~. Measurement s in the Dome

Figure 3 contains histogram plots of Z and 0 measured with the

transducer in the dome. No significant variations were noted between

element measurements in the dome and out of the dome . The ~Lvel’at c

value ol S. in the dome was ~2’.2 0, as compared with 72’.~4 0 for the

bare transducer. Mean value s of ~ were 8. 14 deg and 8.2’ iieg, respec-.

~vei y. Although mean values did not shift appreciably, a ‘hiauige iii

shape of the histograms can be observed. The di stribution of val ues

is somewhat broader with the transducer in the dome . The i’t’ascn icr

this effect is not known . Particular attention was pai l to impedance

measurements on elements at a relative hearing of i80 dog. These

element s look directly at the baffle in the after portion of the

dome . No effect s due to reflections from the baffle were noted.

On the contrary, the stave source level measurements made in

the dome do show evidence of dome effects. Although without beam-

forming c i rcui t ry it is very diff icult to measure meaningfu l valuesof dome tran smission loss , it Is estimated that dome transmissionloss is from O.~ to 1 .0 d13, based upon examination ci ’ st ave scui’ce

1~’

I

100

90

so

~ 60 ~-

~~5O

40 LI30 ~

-

20 ~

I0

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-~~~~~~~~~~

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- - - F . ’ . ’

40 45 30 55 60 65Z - OHMS

)00

90

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HISTOGRAMS OF Z AND ~

OF TRANSDUCER IN DOME AT 5.0 kHz

I’,,

II

- -

~~ - - ~~~ ---~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

level measurements for groups of staves. This value would be applicable

at 000 deg, 090 deg, and 270 d.eg relative bearing.

C. Shipboard Measurements

The average value of Z obtained when individual transducer

elements were measured aboard the USS VOGELGESANG was 50.1 0. The

average value of Z measured in ABLt s dome was 52.2 0. Phase values

aboard the ship averaged 7.9 deg, which compared well with an 8. 4 deg

mean value of 0 measured in ARL’s dome. This phase comparison is

much better than one would expect with the basic phase measuring

accuracies involved. The 2 0 difference between mean values of Z at

LTTS and. aboard ship is more nearly what would be expected with two

entirely different schemes of measurement, both with ±2 0 accuracy.

An additional contribution to this 2 0 difference between L~~S and

shipboard measurements could be accounted for by 61°F water temperature

at Boston versus the L~~S temperature of 67°F.

One defective element was noted during the shipboard measurements;

element 2 of stave 26 was an open circuit. This failure is probably

accounted for by a cable or connector problem because this elementperformed well at ARL.

Figure 4 shows a histogram plot of the impedance values measured

aboard ship. The spread of values is again noted to be favorably

small. Although ARL’s dome measurements at LTTS show a greater spreadwith the transducer in the dome than bare, the shipboard measurement sshow a smaller spread than the LTTS measurements in the dome.

14

U -~~~ ~ ----— --—--- - - ~~

“— - -

~~~~~~~~~

- .-‘~~~~~~~~~~~~~~ - - -

80 ~-

70~

z 60’

~~so r

20’

10 -

0 . — - ‘ - —-.- — 740 45 50 55 60

2 - OHMS

- I

lO r-

~~30~

20

10k

_____00 •5 .10 .15 ‘20

A~~L . U TA S . 69 . 1~ 9S.1)7 . PFO

FI GURE 4 12 . 16 . 69

HISTOGRAMS OF Z AND o OF TRANSDUCERAT 5.0 kHz ABOARD U~S VOGELGESA NG

1,_I

- __ -~~~~~~~~~~ —--~~--- - -~~-—---- - ---~~- ____ _

- ‘ ‘~~~‘ -. ‘

V. COMPARISON OF RESUlTS WITH PREVIOUS TESTS AT THE BOSTON TRF

Tests on the TR-208A, serial BTD-2-69, were conducted at the

Boston T~F in March 1969, just prior to its shipment to AEL. Unfor-

tunately, due to administrative problems these data were not received

at ARL until 15 December 1969. In retrospect, it is unfortunate that

this technical memorandum was delayed pending receipt of the Boston

data, because examination of the data revealed that they are notcomparable with ARL ’s measurements. There are two reasons the data

are not comparable -- (1) the data were measured prior to installationof the AR/F~ vI_1O(V), and thus were measured by using only an oscillo-

scope for E, I, and 0 measurements; and (2) the transducer was drivenwith a set of AN/SQ,S_23 drivers and ~robably was driven stavewise .

If entire staves of the transducer were driven as the elements were

measured, the data would be greatly affected by the shifts in Z and ~values shown in Table I of Section IV. The use of the oscilloscope

method for these measurements results in accuracy much poorer thanthat of the AN/FQM-1O(V).

Because it was evident from examination that these data would notbe comparable with ARL’s data, only a cursory analysis was performed.This analysis bears out the poor comparison expected. For example, on195 of the 432 elements (4~% ), Boston data and ARL data differ by 10 0

or more. It was also noted that 48 elements (ii’~) show Z values fromBoston less than 4O 0, which is the published lower limit on Z. The

very poor comparison between ARL data and Boston data is again pointed

out by the fact that ARL’s data (as described in Section IV.A.) show

30 elements to be out of’ specification--but with high Z values rather

than low ones.

~-

~- - - - - --

~ - -~~~~~ -

IA —~~- -—-—- - ._. - -.-- ---

- - -~~--- ——~~~~~~~- - -- ~~~~~- -~~~~~ ~~~~~~~~~~~~~~~~~~~~ ---

~~~~- -

VI . SU~ 4ARY AND CONCLUSION S

A . Baseline Measurements

~4ith regard to ARL’s measurement of baseline data on the bare

transducer, several conclusions can ho drawn. This transducer

failed the present TRF tests--ll9 of the 452 ’ elements (27 .~’~~)

failed one of the tests. Thirty-five elements showed impedance

magnitude ~,z) values that were too high (greater than 55 O P . .:igI~t ~~four elements showed source level values that were too low (less than

~)b .’) dB). It is interesting to note that there is no overlap between

these groups of elements~ those with high impedance all showed good

source level values. Two conclusions can ho drawn. If one wishes

to accept this particular transducer, consideration should be givento raising the upper limit of Z and lowering the lower limit on

source level. The upper limit on Z should be increased to perhaps

0 while the lower limit on source level should he decreased to

perhaps 95.) d,B. Raising the lower limit on Z was investigated

because several elements with low source level showed relatively low

Z values (45 - 48 1). No conclusion was reached becau8e several low

Z elements checked good on source level. It is interesting to notethat no elements of this transducer fell in the acceptable range

from 40 to 45 0 or the acceptable 0 range -25 ° to 00 . Perhaps this

Indicates that these lower limits should be raised . NUSL (Code 22~ C . l ) ,who is charged with the responsibility of maintaining up-to-date TRF

transducer test specifications, was made aware of these results before

preparation of this menioranthmi.

19

____________

As stated previously, the suggestions to raise the Z limit and

lower the source level limit are based solely upon the desire to

accept the TR-208A, serial BTD-2-69. Because this transducer was

installed aboard ship and subsequently passed required sonar certifi-

cat ion tests, it is assimied that one should accept this transducer.However, it is understood that shipboard system source level measure-ments, though acceptable, were below average for this system. This

i~formatton corroborates ARL ’s low values of source level measuredon many elements.

No attempt was made to compare AEL’s measurements in detailwith those data forwarded from the Boston TRF. Boston measured no

source level values to be compared with ARL’s values; the impedance

data are not comparable for the several reasons stated in Section V.

Boston ’s data show that 48 elements were out of specification withZ values too low when the transducer left the TRF. It is surprising —

that the transducer was shipped to ARL in this condition . However,

ARL’s Z data indicate no elements with values too low. The attempted

comparison of ARL’s data with the Boston TRF data simply serves to

point out the tremendous increase in capabilities afforded by the

AN/FQM-iO(V) Sonar Test Set. This system allows more accurate

measurements of impedance, driving only one element at a time , andallows simultaneous measurement of single element source level. The

importance of the source level measurements cannot be overestimated,

based upon ARL’s measurements on this transducer. No meaningful

correlation existed between those elements that failed the source

level test and their impedance values. Source level must be measured .

Another conclusion reached, after all of the manipulations and

corrections involved in checking source level data, is that TRF source

level specifications should be in terms of’ voltage drive rather thanpower. The AN /FQ!4-iO(V) can normalize voltage (and current)

20

expediently but not power . It also would appear that voltage is a

more meaningful parameter with the AN/SQS-25 system because the drivers

are adjusted for a particular voltage output .

B. 3hipboard Impedance Measurements

The comparison between all of the single element impedance values

(L’rrS without dome, LTTS with dome , and shipboard) is a highly favorable

indication for the widespread application of this type of measurement

for shipboard transducer tosting. It was hoped that individual element

impedance measurements aboard ship in the presence of a dome would

prove to correlate in a meaningful fashion with such measurements made

on the bare transducer. Individual element impedance measurements on

bare transducers have proved to be very effective at revealing failure

modes in the transducer elements. The fact that measurements with and

without domes are identical to within the accuracy of measurement

represents certainly the most favorable correlation that could have

been obtained. It should be emphasized that this favorable comparison

between shipboard and TRF-type impedance measurements is based

strictly upon equivalent driving configurations . ARL’s measurements

aboard ship were made while driving each element individually . Had

similar impedance measurements been made while using shipboard drivers

to power an entire stave at one time, the resulting data would certainly

not have compared favorably with the bare transducer measurements. The

shifts in impedance shown in Table I of Section IV would have prevented

a favorable comparison.

~

- - ~~~~~~~~~~~~~~ —~~-~~~~~~~~~~~~~~~

2~5 December 1969

DISTRIBUTION LIST FORARL-TM-69- 155

UN DER CONTRAC T N00024-69-C-1066

Cop y No.

C ünmiande rNaval Ship Systems CommandDepartment of the Navy

— Washington , D. C. 20360

1 - 4 Attn: SHIPS OOV3M5 Attn : CDR W . E. Trueblood, Code PMS-386

6 Attn : !r. J. Babb, Code P~S-386.37 - 8 Attn : Mr. B. Heany, Code ~4S-386D

9 Attn : Nr. Charles Clark, SHIPS OOV1D

10 CommanderNaval Ship Engineering CenterNorfolk DivisionU.S. Naval StationNorfolk, Virginia 23511Attn : Code 6610

11 - 12 CommanderNaval Undersea Research and Development Cent erSan Diego Division271 Catalina Blvd.San Diego, California 92152Attn: Code 6O~4

13 C ommanding Officer and DirectorU.S. Navy Underwater Sound LaboratoryFort TrumbullNew London , Connecticut 06321Attn : Mr. Gordon Bishop

11+ Office of Naval ResearchResident RepresentativeThe University of Texas at Austin2507 Main BuildingAustin, Texas 78712

23

-I Ui ht~ ~~~~~~~~~~~~~~~~~

_ _ _

_______________________________ —~~~~--- - -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

n_

~~~~~~

- DISTRIBUTION LIST FOR ARL-Th1-69-35 (Cont ’d)

ropy No.

15 Electroacoustics Division, ARL/UT

16 J. E. Stockton, ARL/UT

17 .1. J. Truchard, ARL/UT

18 B. H. Wallace,

19 Library, A.RL/UT

III

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Sonar transducer evaluation

Complex impedance measurements

Shipboard transducer testing

DNC[J~SSLflg

D D .~? ..1473 (BACK ) UN CLASSIFIED(P AGE~ 2) kcurfty Ct.s.IfIc.Uon

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UNCLASSL~EU

THE UNIVERSITY OF TE XASAT AUSTIN

For Official Us. Onl y

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