BODC HEADED DOCUMENT NO. 27793 Applies to BODC Series Ref. Nos.: 33816, 33865, 33877, 33933, 33957, 34008, 34069, 34070, 34149, 34174, 34230, 34242, 47209, 47210 Aanderaa Current Meter/Pressure Recorder The instrument comprises a bottom mounted rig which utilises a Digiquartz sensor and an Aanderaa current meter (with the adaption of a small vane replacing the normal vane) both interfaced into a modified Aanderaa current meter logger. Current meter speed and absolute pressure count are integrated over a pre-selected period (usually 10 or 15 minutes) and sampled by the logger at the same pre-selected time interval, together with spot readings of vane direction, temperature, elapsed time and rig orientation. The pressure sensor consists of a convoluted bellows linked to a 40kHz quartz crystal resonator coupled by piezoelectric action to an electronic resonator. A quartz crystal clock is used for controlling the sampling interval. The data are recorded on magnetic tape as 10 bit binary words in serial form with the frequency count from the pressure sensor stored as most and last significant counts. The pressure sensor pack, containing the Digiquartz type 2-300a quartz crystal pressure transducer but no temperature transducer, is mounted approximately 1m above the rig base, with the current meter 0.7m above the base. The rig is 1.5m in height and the base is formed by a tripod with legs of length approximately 0.7m. The current meter/pressure recorder is usually deployed using a U-shaped mooring (i.e. buoy or pellet float to wire rope to tide gauge to ground line to anchor to wire rope to buoy), but W-shaped moorings are used in conjunction with either current meters or thermistor chains. A W-shaped mooring comprises pellet float to pellet line to sub-surface buoy to current meter or thermistor line to anchor weight to ground line to tide gauge to ground line to anchor weight to wire rope to surface buoy.