STUDY OF FREE-RANGING SHARKS 



OPAQUE VANE — i , — CdS CELL 



441 



KWvVWWvM 



JNWNMW" 



LIGHT SOURCE 



ADJUSTMENT SCREW 



WAMAMM/1 



i. 



v 



STAINLESS STEEL BELLOWS 

 A 



LINEAR TRIMPOT 

 I 1/2 INCH , 



RETURN SPRING 

 CdS CELL 



POINT OF DROGUE 

 ATTACHMENT 



LIGHT 

 SOURCE 



OIL-FILLED 

 HEMISPHERE 



LIGHT SOURCES 



MIRROR 



SHIELDED 

 PHOTOCELLS 

 4 PLACES) 



MAGNET 

 COMPASS JEWELS 



CdS CELL 



RETURN SPRING 



POINT OF DROGUE 

 ATTACHMENT 



LIGHT SOURCE 



1 INCH 



I 1 



1 INCH 



Figure 12 Some representative sensor types used in past CSULB shark transmitters: (A) 

 Depth (pressure). (B) Swim speed (water flow). (C) Compass heading (azimuth). All act as 

 variable resistors. The light/photocell types use low-power LEDs (light-emitting diodes) 

 powered by zener-regulated voltage from the battery. The compass sensor requires four 

 transmitter channels (one for each photocell). 



sensitivities may be used on separate channels, or a network of photocells 

 and resistors may be used on a single channel. 



Depth— Depth cannot adequately be sensed directly by a single resis- 

 tive component. In the shark units, a displacement proportional to depth is 

 achieved by the compression of a sealed, air-filled metal bellows. This is con- 

 verted into a resistance change by a linear trimpot or by moving an opaque 

 vane between a light source (LED, betalight) and a photocell. In the present 

 version, the bellows are partially filled with oil that limits compression and 

 provides absolute protection against overpressure. Some bellows sensors are 



