Seawater probe

Claim 1

Apparatus for measuring conductivity and temperature of seawater, said apparatus comprising a seawater probe comprising a housing, a conductivity cell mounted on said housing so as to be exposed to seawater, a thermistor or other means for measuring temperature, mounted on said housing so as to be exposed to seawater, one or more stable reference resistors, power supply means for supplying an AC current to said conductivity cell, thermistor, and reference resistors, multiplexer means for alternately sampling the AC voltage across said conductivity cell, thermistor, and reference resistors, circuit means for converting the multiplexed AC voltage output of said multiplexer means into an output signal for transmission across said wire, means for storing on or in said probe unique characterization data for said probe in a manner accessible from outside said probe prior to launch thereof, said characterization data comprising data points relating actual conductivity to voltage at said conductivity cell and actual temperature to voltage at said thermistor, and circuitry external to said probe (e.g., onboard ship) for receiving and analyzing said output signal, said circuitry comprising means for receiving said characterization data prior to launch of said probe means for processing said output signal to determine said voltages sampled across said conductivity cell and thermistor, by comparing output signals corresponding to samples taken at said conductivity cell and thermistor to output signals for samples taken across said reference resistors, means for using said characterization data to convert said voltage measurements to actual conductivity and temperature measurements.

Claim 7

The method of measuring seawater conductivity and temperature comprising the steps of providing a seawater probe having a conductivity cell and thermistor exposed to seawater, providing one or more stable reference resistors in said probe, providing an AC current to said conductivity cell, thermistor, and reference resistors, alternately sampling the AC voltage across said conductivity cell, thermistor, and reference resistors, converting the sampled AC voltage into an output signal for transmission across said wire, generating in advance of use of said probe a set of unique characterization data for said probe, said characterization data comprising data points relating actual conductivity to voltage across said conductivity cell and actual temperature to voltage across said thermistor, reading said characterization data from said probe prior to launch thereof, determining the voltages of said sensors (conductivity cell and thermistor) from the signal received from said probe by comparing output signals for samples taken at said sensors to signals for samples taken at said reference resistors, using said characterization data to convert said voltage measurements to actual conductivity and temperature measurements by fitting a curve through said characterization data for a particular parameter (conductivity or temperature) and looking up said actual parameter on said curve using said voltage measurement.

Claim 8

The method of measuring seawater conductivity and temperature comprising the steps of providing a seawater probe having a conductivity cell and thermistor exposed to seawater, providing one or more stable reference resistors in said probe, providing an AC current to said conductivity cell, thermistor, and reference resistors, alternately sampling the AC voltage across said conductivity cell, thermistor, and reference resistors, converting the sampled AC voltage into an output signal for transmission across said wire, generating in advance of use of said probe a set of unique characterization data for said probe, said characterization data comprising data points relating actual conductivity to voltage across said conductivity cell and actual temperature to voltage across said thermistor, reading said characterization data from said probe prior to launch thereof, determining the voltages of said sensors (conductivity cell and thermistor) from the signal received from said probe by comparing output signals for samples taken at said sensors to signals for samples taken at said reference resistors, using said characterization data to convert said voltage measurements to actual conductivity and temperature measurements by fitting a curve through said characterization data for a particular parameter (conductivity or temperature) and looking up said actual parameter on said curve using said voltage measurement.