Ril 1039 C 1933
RIJKSWATERSTAAT The Hague, 10 November 1933
BENEDENRIVIEREN DEPARTMENT
(stamp: RIJKSWATERSTAAT DIR. BENEDENRIVIEREN, D348 LIBRARY)
Concerning: Report echo-sounding equipment of the British Navy
The English hydrographers' judgement concerning the echo-sounding equipment was favourable. All hydrographic vessels of the British Navy (8 in all, those of the Dominions not included) were equipped with similar apparatuses.
Fortunately none of the vessels were operating near London.
The company who supplies the apparatus (Hugh Brs. London) is well known to the English Navy. Indeed, they are keeping in touch, in which the Navy gives
assignments which Hughes Co. executes. The echo-sounding apparatus was developed in this way. At first sound waves were used but approximately 6 months ago they changed to the 'magneto-striction' principle.
Apparatuses of this new type of construction were e.g. delivered to Italy, Denmark and The Netherlands. (HMS Hertog Hendrik in October 1933). They told me that Hughes Co. had delivered already more than 300 'echo-sounders' in all
(of course not all of the new model).
Hughes Brothers' factory is large and well equipped. They employ qualified scientists. They mainly manufacture nautical instruments (compasses, field glasses, sextants, etc.).
It has been alleged that in modest depths of e.g. 1-60 metres the maximal error of the apparatus amounted to 10 cm.
EQUIPMENT INTERIOR. The apparatus is of modest measurements (± 50x40x25 cm). The operation is simple although an ordinary surveyor should not operate i t.
An ordinary car battery of 18 Volt, 100 AU provides electric discharge which shows a
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shape (strong damped sinusoid) . This process causes amagnetic oscillation in a nickel stave of 0 2½ cm and 10 cm long to shape into
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(less damped) while finally a third oscillation is generated (I do not exactly know how, although they have given me the titles of some books,but I could not find them in the library here) into this shape
4-This is the oscillation that is sent and recorded after returning. ln oraer LOavoid sideway oscillations they are aimed by means of a cone shaped sound board.
The oscillation period is
I
/6<000 sec., but despite this extremely fast movement the company's staff is able to photograph all the details as sketched above.
In addition to these oscillations the battery also feeds a small electromotor of½ 0 12 cm. This motor runs almost regularly which can be checked in a way
that i t rotates once per minute. It is essential for the motor to run regularly. By means of turning a knob one can increase or decrease the resistance in order to regulate the rotation.
C
A
The electromotor drives a so-called electric pencil
and a piece of paper on which the results are
registered. The electric pencil moves fast crosswise over the paper, from A to C and back with a speed of
240 periods per minute. Each time when the zero line is passed an oscillation is emitted which is
received back approx. 1/10 sec. later. This
reflected oscillation is amplified by an amplifier and the amplified oscillation is electrically registered in B. The distance AB is therefore covered in the abovementioned 1/10 sec. Thus a figure arises as in the drawing above.
The paper has been prepared in such a way that its becomes dark brown as soon as an electric impulse runs through the electric pencil. As a result of the enormous speed of the electric current time error is avoided in the
registration and actually also the error in depth. This is a considerable advantage of electric registration.
The speed of the electric pencil therefore determines the scale of the registration. The number of registrations is, as can be concluded from the above, 240 per minute.
TEST PROTOCOL. In a concrete tank as sketched here, the distance between AB
was determined for the various stations of the pulley.
Accuracy remained steady (± 10 cm) and slight changes in the distance between AB were immediately registered. It was also
$registered when the pulley was removed further away from B,
but also the distances DB on repetition, because the
oscillation was reflected every time from B to D and back. Also after repeated reflections the by then much larger distance could still be measured with great precision up to± 10 cm. The conclusion of the civil engineers on the test in which the maximum error found was 15 cm and 7½ cm,
respectively (fig. of the registration scale) I consider acceptable.
ADVANTAGES. The apparatus seems to be a multipurpose instrument. It can be
mounted in every iron boat without damaging the bottom and can therefore be
transferred form one boat to the other. It provides many soundings (240 per minute) and apparently with great accuracy. Measurement in shallow waters e.g.
1 m underneath the instrument is feasible but also measurement of great depths. It shows several advantages compared to the German echo-sounder. Not only that i t is half the price but the number of soundings per minute is no less than 60 x larger. At great depths, sounding with the German instrument occurs by telephone with an accuracy of no more than 1%. The personal element plays a role here.
The English instrument not only registers the bottom but also rocks, wrecks,
anchors, remains of poles etc. lying underneath. The Hughes Brs. however did not want to guarantee this as yet. I do not know whether the German instrument registers data substratum. Another advantage is that the personal factor is eliminated completely in the English instrument and that for the fix one just
presses a button to register the exact time when the fix was taken.
DISADVANTAGES. Some of the weak points that are not predominant are the
accuracy obtainable. I was told that the English Navy had also concluded this disadvantage but that already many tests had been made with very many
different types of paper. At my request tests will be carried out with aluminium sheets.
One has to check the steady running of the motor on a gauge (1 rotation per minute). This could be improved e.g. by putting a mark on a conveyor belt with divisions every minute. The running of the motor could then be checked easier and also be checked later on. They assured me however that the velocity of the motor should only be checked± 3x a day.
PRICE. The price estimates approximately NLG 2,800.- (the German one costs NLG 5,600.- ). They stated that they were willing to offer an instrument on trial provided that when the instrument is not purchased the costs of mounting, travel expenses of the mechanic etc. would be compensated.
For further details I refer to the brochures and drawings by the Hughes Brs. Co.
Marian Schillhorn van Veen Beedigd vertaler van Slingelandtstraat 117
2582 XL 's-Gravenhage
(signed) J van Veen, ENGINEER
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