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A simple integrating depth recorder
Deep-Sea Research, 1963, Vol. 10, pp. 457 to 458. Pergamon Press Ltd. Printed in Great Britain.
INSTRUMENTAL
A
NOTES
simple integrating depth recorder
B. V. HAMON, D, J. TRANTER and A. C. HERON (Received 25 Februal3, 1963)
Abstract---A simplc, free-flooding recorder, for use with sampling gear or longlines is described. The recorder gives a variable-density trace on a fixed photographic film, by means of a radioactive source. Maximum and average depths can be read off, also the variation about the average. THERE are few satisfactory instruments available to record the depth at which a particular piece of gear has sampled and it is still common practice to rely on calculations based on length of warp and stray angle. It is seldom sufficient to record maximum depth reached, as can be done with a Kelvin Tube or instruments of the T.S.K. recorder type (Tsurumi-Seiki Kosakusho Co. Ltd., Yokohama, Japan). On the other hand, it is seldom necessary (at least routinely) to keep a detailed record of depth versus time or distance towed (CuRRI~: and FOXTON, 1957), since most samplers give a single bulk or ' integrated ' sample. There appears to be a need for a simple integrating depth recorder which will record the average (modal) depth at which an instrument has sampled, the variation about that average, and also the maximum depth attained. Such an instrument has been designed specifically for use with the Clarke-Bumpus plankton sampler so that its potential for taking stratified hauls at depth could be exploited to the full. It has also been used routinely in a midwater trawling programme and should be suitable for recording the depth of hooks in experimental [ongline fishing.
~O'l
I
INCH j
INCH
Fig. 1. (a) Diagram of depth recorder, with cover plate removed. M : Mounting plate. B : Bourdon tube. T : Twin strip flexure system. S : Stylus. W : Window, with film pack on outside. RP : Retaining plate. (b) Collimating tube on stylus arm. D : Disc of low activity Stxontium 90 foil (United Kingdom Atomic Energy Commission). 457
458
Instrumental Notes
Fig. 1 (a) shows the main features of the depth recorder. A sealed Bourdon tube is used as the pressure sensitive element. The movement of its free end is magnified by the twin strip flexure system and stylus arm, which are similar to those used by CURRIE and FOXTON (1957). In the present instrument, the stylus arm carries a small disc of radioactive foil in a collimating tube (Fig. 1 (b)). The radiation from the tube acts on a photographic film in a light-proof and waterproof package, mounted so that the collimating tube just touches the outside of the package. After development, the film shows a curved trace representing the path of the stylus (Fig. 2). The density of the trace at any point is greater the longer the instrument has been at the corresponding depth. The strength of the source is only about 0'5 microcurie, so that no special handling precautions are necessary. The instrument is free-flooding, and can be used at any depth, provided the Bourdon tube is suitably chosen. The collimating tube dimensions and type of film depend on the application, in particular on the length of time in each operation. The collimating tube in Fig. 1 (b) has been found satisfactory for ~-hr horizontal tows with the Clarke-Bumpus sampler or l~-hr oblique tows with a mid-water trawl. For convenience, a standard dental X-ray film pack was used (llford No. 4; 3 x 4 cm), although a film with lower contrast would be less likely to saturate with long exposures. The film packs are numbered with a moderately sharp stencil stylus, the pressure being transmitted through the pack to the film and leaving a clear trace when the film is developed (Kodak D76 developer, 8 minutes at 20°C). After numbering, the film packs are waterproofed by enclosing each one between two pieces of adhesive household plastic (e.g. ' Fablon '), leaving a ¼ in. wide sealing edge. In use, the film pack is held by a metal backing plate against a window in the recorder casing. It is not necessary to position each film pack accurately, since the film is sensitive enough to record the full arc of movement of the stylus, and the zero depth mark can be easily identified. Typical records are shown in Fig. 2. The records are read from a scale based on a pressure tank calibration (Fig. 2 (d)). Field calibration by lowering the instrument to measured depths would be equally effective, if the cable can be kept nearly vertical. The accuracy of measurement is hard to estimate, and will of course depend on the nature of the trace, but it is not likely to be better than about 5 per cent of full scale. Arrangements have been made for commercial production. Enquiries should be directed to one of the authors. REFERENCES
CURRIER. I. and FOXTON P. (1957) A new quantitative plankton net. J. Mar. Biol. Ass. U.K. 36, 17-32.
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Fig. 2. Depth traces. Spot on extreme right : zero mark. (a) 45-minute horizontal haul with recorder attached to Clarke-Bumpus sampler. Spot on extreme left : maximum depth reached by unopened sampler during loading operations. The larger, slightly oval spot indicates that the haul was made at an almost constant depth (240 m). Faint spots between 240 m and surface : short stationary periods during paying out and hauling in when upper samplers were being attached or removed. (b) 45-minute haul with Clarke-Bumpus sampler. The record shows uneven sampling at depths between 40 and 90 m, although a horizontal haul at 50 m was intended. (c) 90-minute oblique haul, recorder attached to midwater trawl; 700 m wire paid out. This shows an almost uniform sampling, from the intended maximum depth o f 200 m to the surface. (d) Pressure tank calibration curve o f 75 m recorder; spots at 15 m intervals.
INSTRUMENTAL
A
NOTES
simple integrating depth recorder
B. V. HAMON, D, J. TRANTER and A. C. HERON (Received 25 Februal3, 1963)
Abstract---A simplc, free-flooding recorder, for use with sampling gear or longlines is described. The recorder gives a variable-density trace on a fixed photographic film, by means of a radioactive source. Maximum and average depths can be read off, also the variation about the average. THERE are few satisfactory instruments available to record the depth at which a particular piece of gear has sampled and it is still common practice to rely on calculations based on length of warp and stray angle. It is seldom sufficient to record maximum depth reached, as can be done with a Kelvin Tube or instruments of the T.S.K. recorder type (Tsurumi-Seiki Kosakusho Co. Ltd., Yokohama, Japan). On the other hand, it is seldom necessary (at least routinely) to keep a detailed record of depth versus time or distance towed (CuRRI~: and FOXTON, 1957), since most samplers give a single bulk or ' integrated ' sample. There appears to be a need for a simple integrating depth recorder which will record the average (modal) depth at which an instrument has sampled, the variation about that average, and also the maximum depth attained. Such an instrument has been designed specifically for use with the Clarke-Bumpus plankton sampler so that its potential for taking stratified hauls at depth could be exploited to the full. It has also been used routinely in a midwater trawling programme and should be suitable for recording the depth of hooks in experimental [ongline fishing.
~O'l
I
INCH j
INCH
Fig. 1. (a) Diagram of depth recorder, with cover plate removed. M : Mounting plate. B : Bourdon tube. T : Twin strip flexure system. S : Stylus. W : Window, with film pack on outside. RP : Retaining plate. (b) Collimating tube on stylus arm. D : Disc of low activity Stxontium 90 foil (United Kingdom Atomic Energy Commission). 457
458
Instrumental Notes
Fig. 1 (a) shows the main features of the depth recorder. A sealed Bourdon tube is used as the pressure sensitive element. The movement of its free end is magnified by the twin strip flexure system and stylus arm, which are similar to those used by CURRIE and FOXTON (1957). In the present instrument, the stylus arm carries a small disc of radioactive foil in a collimating tube (Fig. 1 (b)). The radiation from the tube acts on a photographic film in a light-proof and waterproof package, mounted so that the collimating tube just touches the outside of the package. After development, the film shows a curved trace representing the path of the stylus (Fig. 2). The density of the trace at any point is greater the longer the instrument has been at the corresponding depth. The strength of the source is only about 0'5 microcurie, so that no special handling precautions are necessary. The instrument is free-flooding, and can be used at any depth, provided the Bourdon tube is suitably chosen. The collimating tube dimensions and type of film depend on the application, in particular on the length of time in each operation. The collimating tube in Fig. 1 (b) has been found satisfactory for ~-hr horizontal tows with the Clarke-Bumpus sampler or l~-hr oblique tows with a mid-water trawl. For convenience, a standard dental X-ray film pack was used (llford No. 4; 3 x 4 cm), although a film with lower contrast would be less likely to saturate with long exposures. The film packs are numbered with a moderately sharp stencil stylus, the pressure being transmitted through the pack to the film and leaving a clear trace when the film is developed (Kodak D76 developer, 8 minutes at 20°C). After numbering, the film packs are waterproofed by enclosing each one between two pieces of adhesive household plastic (e.g. ' Fablon '), leaving a ¼ in. wide sealing edge. In use, the film pack is held by a metal backing plate against a window in the recorder casing. It is not necessary to position each film pack accurately, since the film is sensitive enough to record the full arc of movement of the stylus, and the zero depth mark can be easily identified. Typical records are shown in Fig. 2. The records are read from a scale based on a pressure tank calibration (Fig. 2 (d)). Field calibration by lowering the instrument to measured depths would be equally effective, if the cable can be kept nearly vertical. The accuracy of measurement is hard to estimate, and will of course depend on the nature of the trace, but it is not likely to be better than about 5 per cent of full scale. Arrangements have been made for commercial production. Enquiries should be directed to one of the authors. REFERENCES
CURRIER. I. and FOXTON P. (1957) A new quantitative plankton net. J. Mar. Biol. Ass. U.K. 36, 17-32.
D
i~i~il!i~!ii~iliil'~ii~
i i!!¸ ii!iiiii!ii ¸ i ~ ~!iii.!!iii~i~ ii~!~ i~ i i
C
¸
Fig. 2. Depth traces. Spot on extreme right : zero mark. (a) 45-minute horizontal haul with recorder attached to Clarke-Bumpus sampler. Spot on extreme left : maximum depth reached by unopened sampler during loading operations. The larger, slightly oval spot indicates that the haul was made at an almost constant depth (240 m). Faint spots between 240 m and surface : short stationary periods during paying out and hauling in when upper samplers were being attached or removed. (b) 45-minute haul with Clarke-Bumpus sampler. The record shows uneven sampling at depths between 40 and 90 m, although a horizontal haul at 50 m was intended. (c) 90-minute oblique haul, recorder attached to midwater trawl; 700 m wire paid out. This shows an almost uniform sampling, from the intended maximum depth o f 200 m to the surface. (d) Pressure tank calibration curve o f 75 m recorder; spots at 15 m intervals.