New Generation CTD Sensor Systems

A new microprocessor based CTD sensor unit is described. The uP is used to vary the A/D conversion process to achieve 16 bit resolution at a measurement rate of 500 per second to 18 bit resolution at 30 per second. Software control of resolution, sampling rate and sampling sequence permit the sensor unit to be software configured for a wide variety of missions. New pressure and conductivity sensors are expected to substantially improve the system accuracy. The new conductivity cell design has 7 electrodes which are all relatively remote from the external measurement volume (approximated by a 2 cm diameter sphere). This "recessed electrode" concept is expected to eliminate calibration drift due to electrode contamination, thus ensuring excellent long term stability.