down hole instrumentation will carry out automatically the following sequence a energize a transducer eg temperature to voltage contained in the transducer housing 26 b convert the voltage analog the output of the transducer to a digital word in which binary 1 39 s and 0 39 s are identified by discrete voltage levels this digital word is then temporarily stored in a shift register not illustrated in the electronic cavity 25 c in a timing sequence consistent with the practicality of the system serialize the digital word by applying clock pulses to the shift register d by means of buffering and power amplifiers not illustrated use the serial digital word to activate the motor of the motor valve 27 whereby a portion of the drilling fluid is permitted to exit from the wash pipe 23 and enter the annulus 19 without having passed through the restrictive nozzles in the drill bit 11 because the valve is actuated by the digital word derived from the transducer the releasing of the drilling fluid from the wash pipe to the annulus will occur in a sequence of go no go events indicative of the physical measurement made by the transducer the electrical power required to carry out the foregoing operations is provided typically by a battery of dry cells not illustrated contained in the annular power supply cavity 28 electrical.