Patent ID: 6646454
Filing Date: 2003-11-11
Classification: G01B,G01R

Abstract:
The method of measuring from only one of its ends the length of a cable whose capacitance per unit length is previously known, comprising the steps of:selecting an oscillator circuit into which a desired capacitor may be selectively inserted, the oscillator circuit being characterized by an operating frequency substantially proportional to the capacitance value of the inserted capacitor; inserting into the oscillator circuit a reference capacitor whose capacitance value is known; then operating the oscillator circuit a predetermined period of time while counting a first number of oscillations it generates; thereafter inserting the one end of the cable into the oscillator circuit in lieu of the reference capacitor, and again operating the oscillator circuit for the same predetermined period of time while counting a second number of oscillations it then generates; comparing the first and second numbers of oscillations to obtain a ratio; combining the ratio with the known capacitance to produce a result indicating cable capacitance; and then combining the cable capacitance with the previously known capacitance per unit length of the cable to produce a result indicating the length of the cable.