temperature transducer 14 is again supplied by an appropriate power supply in an electronics package 78 via electrical leads 74 and 76 the leads 74 and 76 are disposed within the borehole instrument wall 60 and within the thermal isolator insert 51 and terminate at the tool contacts 72 and 70 respectively fig3 a illustrates one means for thermally isolating the temperature transducer 14 from the wall 60 of the borehole instrument it should be understood that the desired thermal isolation of the temperature transducer 14 can be obtained using other embodiments such as fabricating the housing 12 with a thermally insulating material fig4 illustrates conceptually the temperature sensor assembly 10 disposed in a well borehole for measuring temperature of borehole fluids a borehole instrument 84 is suspended in a well borehole 92 that penetrates earth formation 90 the borehole instrument is operationally connected to a lower end of a data conduit 82 by a suitable connector 83 the upper end of the data conduit 82 is operationally connected to a conveyance means 80 at the surface 96 of the earth the conveyance means 80 is operationally connected to surface equipment 89 which can power and transmit down link data to the borehole instrument 10 and receive and process up link data transmitted from the temperature sensor assembly 10 and other instrumentation within the borehole instrument 84 the temperature sensor 10 responds primarily to temperature of borehole fluid in the annulus.