BODC HEADED DOCUMENT NO. 34098 Applies to BODC Series Ref. Nos.: 41066, 41091, 41110, 41134, 41158, 41171, 41214, 41238, 41343, 41447, 41539 I.O.S. Off-Shore Pressure Recorder Mark III The main part of the capsule is a forged aluminium sphere of 0.66m internal diameter, which contains the data logging system, acoustic command and release units and all battery supplies. Each half of the sphere is bolted to a central equatorial ring, a seal being provided by O rings. There are twelve outlets through this ring for Marsh Marine type electrical connectors. The sphere is housed in a free flooding tubular aluminium alloy frame. Also mounted on this frame are 2 pressure transducers, a sea temperature unit, 2 subsidary platinum resistance thermometers for measuring sea temperature and 2 wound nickel scrolls that act as acoustic pinger beacons. The frame and sphere, complete with attachments, have a positive buoyancy, and in order to anchor them, they are mounted on a steel tripod. The tripod is attached to the main frame by a central pyro-release unit. The system incorporates a commercial data logger modified to operate in the deep sea capsule. The logger will accept input from a total of twelve separate sources or channels. The temperature and pressure sensors have variable frequency outputs. The frequencies are counted over a 890 second period and the total count for each channel is then recorded during a scan of all channels which lasts for 10 seconds. Thus the averaged integrated pressure and temperature values are logged every 15 minutes. Temperature is measured to correct for the temperature coefficient of the pressure transducers.