sample is thus determined the determined wellbore fluid sample resistivity is representative of the salinity of the borehole fluid sample in the each conductivity cell c the conductivity measurements are obtained in each of the cells c and an average of these values is determined and stored as the representative salinity of the wellbore fluid at the sample depth of interest the temperature sensor 30 is usually a thermal resistive device with a linear resistance to temperature relationship for temperature measurement resistance r of a thermal resistive device depends on the material 39 s resistivity u03c1 the structure 39 s length l and cross section area a the change in temperature can be calculated by measuring the change in resistance by the following formula using initial values of resistance and temperature r o and t o and the temperature coefficient u03b1 a platinum resistance thermometer prt is preferably used as the temperature sensor 30 platinum has a higher temperature range good stability and low tendency to react with surrounding material as required for downhole conditions these unique properties of platinum enable prt to operate in temperature range of u2212 272 5 u00b0 c to 961 78 u00b0 c the platinum resistor of temperature sensor 30 is typically fabricated on.