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F. B. (Fedor Bogdanovich) Miller.

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iYDROMECHANIC



STRUCTURAL
MECHANICS



1 PPLIED

,03 HEMATICS



ml




DYNAMIC WAVE-HEIGHT RECORDER
TYPE 286-1A



by
P.B. Miller



INSTRUMENTATION DIVISION



RESEARCH AND DEVELOPMENT RETORT



August 1957



Report 1123



»IWC-TMB-6»8 (11-56)



DYNAMIC WAVE-HEIGHT RECORDER
TYPE 286-1A



by

F.B. Miller



August 1957 Report 1123



TABLE OP CONTENTS

Page

ABSTRACT 1

INTRODUCTION 1

PART I - DESIGN 2

GENERAL 2

GAGE 2

CARRIER SYSTEM 2

ADJUSTMENT 3

BALANCING UNIT 4

PART II - INSTALLATION, OPERATION, AND MAINTENANCE 5

INSTALLATION 5

OPERATION 5

MAINTENANCE 6

PERSONNEL AND ACKNOWLEDGMENTS 7

REFERENCES 19



ii



LIST OP ILLUSTRATIONS

Page

Figure 1 - Wave-Height Recording Console 11

Figure 2 - Dynamic Wave-Height Recorder, 12

TMB Type 286-1A,
Top, Front, and Bottom Views

Figure 3 - Bridge Balancing Unit, 13

TMB Type 286-2A

Figure 4 - Dynamic Wave-Height Recorder, l4

TMB Type 286-1A, Schematic Diagram

Figure 5 - Bridge Balancing Unit, 15

TMB Type 286-2A, Schematic Diagram

Figure 6 - Sanborn Company Driver Amplifier, 16

Schematic Diagram

Figure 7 - Sanborn Company Power Supply, 17

Schematic Diagram

Figure 8 - Sanborn Company Recorder, 18

Interconnection Diagram



iii



ABSTRACT

This report describes a dynamic wave-height recording
system which utilizes an insulated wire probe as a
capacitance-type transducing element . The electronic portion
of the system is designed as a plug- in component of a
commercial direct-writing recorder console. The output of
the system is in the form of a rectangular plot of wave
height versus time,, Schematic diagrams and operating
instructions are included.



INTRODUCTION

In a facility engaged in ship hull design, the problems
associated with the testing of the various models in waves
dictate that some types of tests be made in waves of known
and controlled dimensions. The waves desired for these tests
may be produced by the various wavemakers available at the
David Taylor Model Basin, It is desirable to be able to
record these wave profiles and produce a permanent record
for analysis and correlation with other data. Furthermore,
such a record allows the wavemaker to be more easily adjusted
to the desired condition.

In earlier work, some wave profile recording was done
by photographing a grid marked on one wall of the basin. As
the wall had an adverse effect on the wave shape, and as
any imperfections in the wall surface further distorted the
wave, the method left much to be desired. Also, the results
were not available until after the film was developed.

During 1952 5 the TMB Type 145-A Dynamic Wave-Height
Recorder" 1 was designed and produced and has met with notable
success in a number of tests since that time. This system
exhibited excellent linearity characteristics, and the gage
was easy to produce and simple to clean or replace when
necessary. No photography was required, and the gage
dimensions were small enough to cause little effect on the
wave under investigation.

In order to meet the needs of the expanding test programs
of the Hydromechanics Laboratory, more channels of wave-height
recording instrumentation were desired. In the meantime, a
commercial direct-writing recording system featuring semimodular
construction became available. It was decided to redesign the
circuits of the older Type 145-A recorder and package the
electronic portion in a plug-in chassis which could be used
with the new recording console. All the_ desirable features

_1 References are listed on page 19



of the prototype were retained and several improvements
contributing to simplicity of operation were incorporated in
the new design. The calibration method has been simplified,
as has the bridge balancing -null detection operation.. The
new units are known as TMB Type 286-1A and are used with the
Sanborn driver amplifier 2 , power supply 3 , and recorder „



PART I

DESIGN

GENERAL

The wave-height recording system consists of a gage, the
associated electronic system, and the recorder,. The gage is
essentially a capacitive transducer, the capacity varying
linearily with the water height „ This gage is used in a
capacitive bridge energized with a 10-kc carrier signal.
The signal recovered from this bridge is demodulated in a
phase-sensitive detector and further amplified . This
signal is then fed to* the Sanborn driver amplifier and to the
recording pens.



GAGE

The gage consists of a length of No. 28 enameled wire,
stretched taut, insulated from the water, and positioned
vertically through the water surface. The conductor forms
one plate of the capacitor, the water forms the other plate
of the capacitor, and the enamel is the dielectric. Since
the plate area formed by the water varies linearily with
the height of the water (if the thickness of the enamel
dielectric is uniform), the capacity of the gage is a linear
function of the water height. The gage gives a large AC of
about 50 uuf per inch of water. For a more complete
discussion of the gage, see TMB Report 859, "An Electronic
Wave-Height Measuring Apparatus o"" 1

CARRIER SYSTEM

Bridge drive is provided by a bootstrap oscillator and
driver of fairly conventional design. This drive is link
coupled into the bridge. Both the input and the output of
the bridge are resonated at the carrier frequency. Thus, a
high-drive voltage is obtained at a small outlay in power,
and the bridge output is multiplied by the resonant output
condition. Bridge output signal shifts 180 degrees in
phase with change in direction of bridge unbalance.



The bridge output is fed through an attenuator to a
pair of cascaded voltage amplifier stages . The output of
this second voltage amplifier is transformer coupled in
push-pull into the modulator grids. The carrier is
injected into these grids in parallel. The phase sense is
recovered by this action,, The signal is then fed to a
demodulator and voltage amplifier, then to the Sanborn
driver amplifier.

The injected carrier is taken from the driver amplifier
plate and fed to the injection point by means of a cathode
follower„

In order to detect bridge balance, a device to indicate
bridge signal voltage is necessary. In this unit, this
function is accomplished by removing the injected carrier
from the modulator and disabling one side of the demodulator,
leaving the other side as a straight amplifier. This removes
the phase -sensitivity of the demodulator, and any signal
present drives the recorder in one direction. It is then
possible to balance the bridge, using the minimum recorder
deflection as an indication of bridge balance.

In order that the unit may be used with two or more
gages by means of a multichannel balancing unit (for example,
TMB Type 286-2A, shown in the circuit section of this manual),
a switch is installed to disconnect the internal bridge
balancing system. This allows the components in the multi-
channel balancing unit to complete the bridge and supply the
balancing function, see PART I, BALANCING UNIT, page 4„

The front panel GAGE connector is paralleled by pins
6 and 9 of connector J-204 on the rear apron of the driver
amplifier (9 is ground). Thus, it is possible to bring the
gage cables into the rear of the unit rather than the front.

When two or more carrier systems are used close to one
another, the carrier oscillators may beat with each other
and produce a cyclic variation in the output signal at the
difference frequency of the individual oscillators.
Provision has been made in the Type 286-1A for synchronizing
the oscillators to avoid this undesirable effect.

The positioning of the recording stylus is controllable
from the front panel of the Type 286-1A.



ADJUSTMENT

The following adjustments are made as part of the
construction and should remain fixed short of a major change
in one of the associated components.

3



The oscillator frequency determining elements and the
bridge driver tank circuits are fixed-tuned and should
require no attention . Should the frequencies of a number
of these units be very different, it may not be possible to
synchronize the oscillators. Should this problem arise,
each of the oscillators should be set reasonably close to a
10-kc secondary frequency standard.

Phasing of the unit is accomplished by a slight variation
in the tuning of the bridge output. This is a broad adjust-
ment and is not overly critical . The phasing adjustment should
be made for maximum output with a slight capacitive unbalance
in the bridge circuit.

The bridge DRIVE (and injected carrier) is adjustable by
means of a deck-mounted potentiometer . This control is used
as a rough sensitivity control, with the front panel
PINE SENSITIVITY control being effective over a range of
about 10 percent of full scale. With the FINE SENSITIVITY
control at about midposition, the DRIVE control on the deck
should be adjusted until the full-scale deflection of the
recording stylus is satisfactory for the use intended. An
approximate full-scale signal may be secured by balancing the
bridge, setting the SENSITIVITY control to the 4-ineh-full-
scale step, then rotating the 0-0.001 ROUGH CAP. BALANCE
control one step in either direction. This adds or subtracts
100 u.uf in the gage arm, corresponding to approximately
2 inches change in the water level.

The CAL„ ADJ. allows the calibration step to be adjusted
over a narrow range. It is intended that the calibration
step be full scale on the 4-inch full-scale SENSITIVITY
step. The CAL. ADJ. control should be adjusted until the
calibration step corresponds to a 2-inch change in submersion
of the gage while on the 4-inch full-scale SENSITIVITY step.

In order to facilitate bench work on these units, the
bridge components are chosen so that the unit may be balanced
with no gage or cable connected. In operation, more than
100 feet of RG 62/u coaxial cable can be used, as the system
will balance with more than 4000 u.u.f of external capacity.



BALANCING UNIT

When it is desired to record wave heights from two
gages with the same wave-height recorder, a TMB Type 286-2A
Balancing Unit may be used to couple the two gages to the
single recording unit, and the recorder may then be switched
to either of the gages. The internal bridge balancing system



of the recorder is then disconnected by means of the switch
provided for this purpose, and the balancing function is taken
over by two sets of similar components in the balancing unito
Two sets of the bridge-balancing components are necessary in
order to achieve a balance on both gages simultaneously
because of the different values of capacitance and dissipation
associated with the individual gages. The balancing unit is
pictured in Figure j5, with the corresponding schematic
diagram in Figure 5°

PART II

INSTALLATION, OPERATION* AND MAINTENANCE

INSTALLATION

Installation of the Type 286-1A unit is similar to the
Type 145-A. The gage is positioned through the resting
surface of the water and clamped in this position. Approxi-
mately half of the gage should be immersed in the water. The
gage is then connected to the wave-height recorder by means
of any good quality coaxial cable. As the Type 286-1A is
used in the Sanborn console, the connections to the unit
are automatically made when the unit is placed in the rack.
The connections between the driver amplifier, power supply,
and recorder are already made by plug-in cables 4 inside the
rack and should offer no problems „

Should it be desired to use two gages with a single
Type 286-1A unit, a bridge balancing unit, Type 286-2A, may
be used to properly couple to the two gages. The internal
bridge balancing controls must be switched out of the system
by means of the INT-EXT deck switch in the Type 286-lA. The
GAGE connector and the two gage cables are then connected
to the bridge balancing unit. The functions of the ROUGH
CAP BALANCE, CAP. BALANCE, and RES. BALANCE on the Type 286-1 A
are then taken over by corresponding controls in the bridge
balancing unit. The gages are each balanced in turn in the
same manner as described in the next section. It is then
possible to record from either gage as desired.



OPERATION

Before use, the system should be connected to the power
line, turned on and allowed to come to operating temperature.
The direct-coupled amplifiers in the system may be expected
to drift during this period. A warm-up time of approximately
15 minutes should be allowed before measurements are made.



With the water still, the unit may be balanced by
depressing the OPERATE-BALANCE switch and advancing the
SENSITIVITY control as far as possible with the recording
stylus remaining on the paper . Then the CAP. BALANCE and
RES, BALANCE are alternately adjusted to obtain a minimum
indication on the recorder The SENSITIVITY is then advanced
and the process repeated . This operation is repeated until
a null indication Is obtained on the 0.6-Inch full-scale
SENSITIVITY step. The OPERATE-BALANCE switch is then
released. The SENSITIVITY control is then rotated back to
OFF and the position to which the stylus shifts is noted.
The SENSITIVITY control is then rotated back to the 0.6-
inch full-scale step, and the CAP. BALANCE control (or
controls, if necessary) rotated until the stylus shifts to
the same position to which it moved when the SENSITIVITY
control was placed in the OFF position. The stylus will
then be found to stay in the same place when the SENSITIVITY
control is rotated, provided that the bridge remains in
balance. The SENSITIVITY control is then placed on the
desired step and the stylus positioned to the center of the
paper (or to the desired zero position) by means of the
STYLUS POSITION control.

In calibrating the system, the SENSITIVITY control
should be turned to the 4-inch full-scale step. This is
because the calibration built into the unit represents a
change in water depth of approximately 2 inches in each
direction, or a total of 4 inches. After calibration,
the SENSITIVITY control may be returned to the desired
position. The system is then ready for use.



MAINTENANCE

The electrical components in the Type 286-1A Dynamic
Wave-Height Recorder are all operated well within their
ratings and should give very little trouble. The console
has a blower for cooling.

Cables should not be walked upon nor permitted to
stay in the water.

The gage should be cleaned occasionally with a soft
cloth. This is necessary to remove the foreign matter that
collects on the wire. Holes in the enamel have the effect
of a leaky dielectric and prevent the proper balancing of the
bridge. These holes will seldom be found in a new wire, but
will sometimes develop after use. In the extreme case, they
are evidenced by the inability to reach a resistance balance
of the bridge.

6



In the event of a damaged wire, a new length of No, 28
enameled wire should be installed. It is of interest to
note that ordinary Belden enameled wire has proven more
satisfactory than the more expensive types now on the market.
The new wire should be fitted with a bayonet-type fastening
on the lower end and must be cleaned and soldered in place
at the upper end. In preparing new wires, it is generally
more economical to discard the old bayonet fitting and drill
a new one from 1/4 inch diameter bakelite rod than to attempt
to reuse the bayonet device. The wire itself is completely
insulated from the water with automotive windshield sealing
compound or the equivalent. With the gage properly positioned
in the water, a d-c resistance measurement of less than
20 megohms indicates a questionable gage.

Because adjustment of the phasing of the unit is not
normally expected to change, the phasing procedure is
included under PART I, ADJUSTMENT.



PERSONNEL AND ACKNOWLEDGMENTS

The general design of the instrumentation described in
this report was the work of Mr. R.G. Tuckerman of the
Instrumentation Division. The detail design and final
adjustment and testing of the equipment was the work of the
author, also of the Instrumentation Division.



PARTS LIST FOR DYNAMIC WAVE HEIGHT RECORDER
DTMB TYPE 286-1A



C-l 0.10 [if ±1 percent Sprague Vitamin-Q,

C-2 0.01 u.f ±1 percent Sprague Vltamln-Q

C-3 l40 wif Hammarlund MC-140S

C_4 0-0.011 [if Cornell Dubllier CDA-5

C-5 0.005 [if Silver Mica

C-6 3900 uuT approx. Silver Mica

C-7 68 jjLjxf* Silver Mica

C-8 50 [i[if Hammarlund MC-50S

C-9 0.11 jxf ±1 percent Sprague Vitamin-Q

C-10 0.01 [if ±1 percent Sprague Vitamin-Q

C-ll 7000 [i[if approx. Silver Mica

C-12 0.15 ^f ^00 v

C-13 0.15 U-f ^00 v

C-l4 0.01 [if 400 v

C-15 0.15 M-f 400 v

C-16 0.01 [if 400 v

C-17 470 [i[if Silver Mica

C-18 0.15 M-f ^00 v

C-19 0.01 M-f 400 v

C-20 2400 [i[if approx. Silver Mica

C-21 0.001 u.f 400 v

C-22 1200 [i[if approx. Silver Mica

C-23 0.15 M-f ^00 v

C-24 100 uu.f Silver Mica

C-25 0.01 |if 400 v

C-26 0.01 u.f 400 v

C-27 0.01 [if 400 v

C-28 0.1 [if 400 v

C-29 125 mf Silver Mica

C-30 125 MM-f Silver Mica

C-31 700 [i[if Silver Mica

C-32 700 [i[if Silver Mica

C-33 .002 [if Silver Mica

C-34 .002 |xf Silver Mica

C-35 0.25 M-f ^00 v

R-l 125 k 1/4 percent wire wound precision

R-2 100 k l/4 percent wire wound precision

R-3 100 ohm 10 turn potentiometer

R-4 100 k l/4 percent wire wound precision

R-5 100 k 1/4 percent wire wound precision

R-6 1.5 k ± 1/4 percent

R-7 0.9 k ± l/4 percent

R-8 1.6 k ± 1/4 percent

8



R-9 2k ± 1/4 percent

R-10 4k ± 1/4 percent

R-ll 5k ± 1/4 percent

R-12 9k ± 1/4 percent

R-1J 16 k ± 1/4 percent

R-14 20 k ± 1/4 percent

R-15 40 k ± 1/4 percent

R-16 1 k 1/2 watt

R-17 22 k 1 watt

R-18 4.7 k 1/2 watt

R-19 1 meg 1/2 watt

R-20 680 ohms 1/2 watt

R-21 1000 ohms 2 watt potentiometer

R-22 4.7 k 1/2 watt

R-23 1 k 1/2 watt

R-24 1 k 1/2 watt

R-25 220 k 1/2 watt

R-26 220 k 1/2 watt

R-27 22 k 1/2 watt

R-28 3.9 k 1/2 watt

R-29 47 k 1/2 watt

R-30 47 k 1/2 watt

R-31 10 k 1/2 watt

R-32 220 k 1/2 watt

R-33 10 k 1/2 watt

R-34 47 k 1/2 watt

R-35 220 k 1/2 watt

R-36 4.7 k 1/2 watt

R-37 180 k 1/2 watt

R-38 1 meg 1/2 watt

R-39 100 k 2 watt potentiometer

R-40 47 k 1/2 watt

R-4l 4.7 k 1/2 watt

R-42 2.2 k 1/2 watt

r_43 470 k 1/2 watt

r_44 470 k 1/2 watt

R-45 220 k 1/2 watt

R-46 220 k 1/2 watt

R-47 220 k 1/2 watt

R-48 220 k 1/2 watt

R-49 56 k 1/2 watt

R-50 15 k 1/2 watt

R-51 470 k 1/2 watt

R-52 470 k 1/2 watt

R-53 2.7 k 1/2 watt

R-54 2.7 k 1/2 watt

R-55 15 k 1/2 watt

R-56 27 k 1/2 watt

R-57 27 k 1/2 watt

R-58 47 k 1/2 watt



R-59
R-60
R-6l
R-62
R-63
R-64
R-65
R-66



270 k
1 meg
1 meg
270 k
47 k
120 k
120 k
10 k



1/2 watt
1/2 watt
1/2 watt
1/2 watt
1/2 watt
1/2 watt
1/2 watt
2 watt potentiometer



L-l 5 mh Toroid, Bumell Type TC-3, 27 Turn Link Added

L-2 10 mh Toroid, Bumell Type TC-3

L-3 100 mh Toroid, Burnell Type TC-3

L-4 100 mh Toroid,, Burnell Type TC-3, 31 Turn Link Added

T-l 4;1 Transformer Audio Dev. Co. Type A-5311

Resistors 5 percent except as noted



10




Figure 1 - Wave- Height Recording Console

Two TMB Type 286- 1A wave- height units are shown installed in the upper part of the
Sanborn 4- Channel Recorder Console. The two blank panels are reserved for future units
of the same type.



11



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Figure 2 - Dynamic Wave-Height Recorder, TMB Type 286-1A Top, Front,

and Bottom Views



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18



REFERENCES



1. Campbell, W.S., "An Electronic Wave-Height Measuring
Apparatus/' TMB Report 859, October 1955.

2. Sanborn Driver Amplifier Schematic, from Driver
Amplifier Model 150-200B Replacement Parts List, Sanborn
Company, Cambridge, Mass. (Reproduced as Figure 6 of this
report. )

3° Sanborn Power Supply Schematic, from 60 Cycle Power
Supply Model 150-400 Replacement Parts List, Sanborn Company,
Cambridge, Mass. (Reproduced as Figure 7 of this report.)

4. Sanborn Recorder Interconnection Diagram, from Four
Channel Recorder Model 154-100B Replacement Parts List,
Sanborn Company, Cambridge, Mass. (Reproduced as Figure 8
of this report. )



19



INITIAL DISTRIBUTION

Copies

9 Chief, Bureau of Ships, Technical Library (Code 312)

5 Technical Library
1 Applied Science Branch (Code 370)
1 Special Devices Section (Code 851 )
1 Technical Assistant to Chief of the Bureau
(Code 106)

2 Chief of Naval Research

1 Director, U.S. Naval Research Laboratory,
Washington 20, D.C.

1 Commanding Officer and Director, Naval Electronics
Laboratory, San Diego 52, California

1 Commander, U.S. Naval Ordnance Laboratory, White Oak,
Silver Spring 19, Maryland

1 Commanding Officer and Director, U.S. Navy Underwater
Sound Laboratory, Fort Trumbull, New London, Conn.,
Attention Mr. Whannel

1 Commander, Norfolk Naval Shipyard (Code 227),

Underwater Explosion Research Field Unit, Norfolk, Va.

1 Director, National Bureau of Standards, Washington, D.C,

1 Director, U.S., Coast and Geodetic Survey, Department
of Commerce, Washington, D.C.

1 Beach Erosion Board, U.S. Army Engineers, Little Falls
Road and MacArthur Blvd., N.W., Washington, D.C.

1 Director, Experimental Towing Tank, Stevens Institute
of Technology, 711 Hudson St., Hoboken, N.J.

1 Director, Woods Hole Oceanographic Institution,
Woods Hole, Mass.

1 Director, St. Anthony Falls Hydraulic Laboratory,
University of Minnesota, Minneapolis, Minn.

1 Dr. Per Bruun, College of Engr., Univ. of Florida,
Gainesville, Fla.

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Online LibraryF. B. (Fedor Bogdanovich) MillerDynamic wave-height recorder type 286-1A → online text (page 1 of 2)