| 摘要 |
The length of an electrical cable is measured from only one of its ends, even though much of the cable may not be visible and its remote end may not be accessible. The ends of a conductor pair are selected to serve as contacts for a test capacitor. A reference capacitor having known capacitance value, and the test capacitor, are alternately inserted into an oscillator circuit while measuring the oscillator frequency. The two oscillator frequencies are compared to provide a ratio, which is then mathematically combined with a number indicative of the capacitance per unit length of the cable so as to produce an output number representing cable length.
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