An Automatic Computer-Controlled System for the Measurement of Cable Capacitance

A description is given of the application of automation to a classical measurement problem-determining the capacitance parameters of multiconductor communication cables. These parameters are important in the manufacture of cables and determine such factors as transmission efficiency, crosstalk, and noise. Although the desirability of automating these measurements has long been recognized, the problem of controlling stray capacitance in the switching equipment and connecting leads has previously prevented such automation. This problem has now been overcome by the use of a three-terminal guarded automatic bridge to measure the individual direct capacitances between conductors and a digital computer to calculate the desired parameters from these measurements. The benefits that have been realized by the inclusion of the computer in the measurement system are emphasized-increased speed, elimination of errors, flexibility of operation, data reduction and presentation, and self-testing.