ON-CRUISE CALIBRATION OF XBT PROBES

A procedure is described to calibrate XBT probes at one temperature po int immediately before launching. The individual XBT temperature offse ts are determined by using a stirred calibration bath and a stable, ac curate reference thermometer designed for field use. The proposed cali bration procedure increases XBT temperature accuracy considerably, whi le it hardly raises time and effort spent on standard XBT drops. The p erformance of the system in the field and in the laboratory is describ ed. It is shown that the achieved temperature accuracy is about 0.03 K , and is basically limited by the used reference thermometer.