A New Thermistor Chain for Underwater Temperature Measurement

The Applied Physics Laboratory has recently completed a series of underwater temperature measurements using a new thermistor chain developed in collaboration with Fathom Oceanology, Ltd., and Sippican Corporation. The chain is a 750 ft long cable with plastic nose and tail fairings to reduce the cable drag coefficient to less than 0.20. Thirty thermistors in glass envelopes are mounted in the nose pieces and exposed to the free stream. Response time constant in sea water when towed at 4 kts is 180 msec. Tests in January 1976 off the west coast of St. Croix have confirmed the reliability of the chain. The desired accuracy of deg Celsius has been obtained. Each thermistor is serviced by a pair of twisted #30 insulated wires which are carried in the tail fairings. A total of 77 pairs of wires was provided in two bundles, and there is space for an additional 36 pairs. The end of the cable is weighted with an 850 lb faired body which contains a pressure transducer and acoustical devices for tracking.