FIELD: drill-hole research; applicable in determination of velocity of downhole instruments. SUBSTANCE: method is based on measurement of velocity of load-carrying logging cable with downhole instrument secured to cable end. Applied preliminary to armor of load-carrying logging cable are magnetic marks presenting sequence of sections of different magnetization intensity. Arranged along moving load-carrying logging cable are two readers reading magnetic marks and converting them into corresponding signals. Distance between readers is fixed and memorized in form of respective signal. Standard deviation and correlation function of output signals of corresponding readers are determined. Coefficient of output signals correlation of readers is determined as ratio of correlation function and production of standard deviations of readers output signals. Prior to determination of said correlation function, output signals of corresponding readers are delayed so that obtained value of said correlation coefficient of output signals of said readers is maximum. Direction and velocity value of downhole instrument are determined by using values of distance between readers and delays duration of reader output signals. Device has besides said readers, two computing units of standard deviation, two delay units, multiplier unit, control unit, computer, memory unit, registration unit and also successively connected unit for determination of correlation function, correlation coefficient computing unit and processing unit. Output of registration unit serves as device output. EFFECT: higher accuracy of determination. 2 cl, 1 dwg
