BODC HEADED DOCUMENT NO.  27840                         
                                                                                
 Applies to BODC Series Ref. Nos.:   33982,  33994,  34033,  34045,  34057,
                     34082,  34094,  34101,  34113,  34125,  34137,  34198,
                     34205,  34217,  34229,  34254,  34266,  34309,  34310,
                     34322,  34334,  36851,  36918,  47222,  47234,  47246,
                     47271,  47295,  47302,  47314,  47351,  47387

    Teleost Pressure Recorder                                                   
    This instrument was developed at I.O.S. Bidston.  Each recorder consists of 
    a  Bell  and  Howell  strain gauge or a Digiquartz pressure transducer. The 
    strain gauge sensor uses a  Bell  and  Howell  type  4-306  transducer  and 
    operates  as  a phase shift oscillator whose frequency is controlled by the 
    ratio of output to  input  voltage  of  the  transducer  Wheatstone  bridge 
    network.  The  quartz  crystal  pressure  sensor  consists  of a convoluted 
    bellows linked to a 40kHz quartz crystal resonator coupled by piezoelectric 
    action  to  an electronic resonator.  The pressure and temperature recorder 
    consists of an Aanderaa current meter type logger modified to accept  input 
    from  a  pressure  sensor  containing  a  Bell and Howell strain gauge or a 
    Digiquartz pressure transducer and a platinum resistance thermometer.   The 
    pressure  and temperature transducers are mounted in the same heat sink for 
    compatible data. The pressure sensors are mounted in a protective frame  of 
    dimensions  1.75m  by 1.14m by 0.66m, attached to a ballast plate or frame. 
    Teleost recorders are deployed as pop-up moorings and released  from  their 
    ballast frames by firing a pyrotechnic release by acoustic command.