초록 ▼

A non-intrusive electrical cable tester determines the nature and location of a discontinuity in a cable through application of an oscillating signal to one end of the cable. The frequency of the oscillating signal is varied in increments until a minimum, close to zero voltage is measured at a signa

A non-intrusive electrical cable tester determines the nature and location of a discontinuity in a cable through application of an oscillating signal to one end of the cable. The frequency of the oscillating signal is varied in increments until a minimum, close to zero voltage is measured at a signal injection point which is indicative of a minimum impedance at that point. The frequency of the test signal at which the minimum impedance occurs is then employed to determine the distance to the discontinuity by employing a formula which relates this distance to the signal frequency and the velocity factor of the cable. A numerically controlled oscillator is provided to generate the oscillating signal, and a microcontroller automatically controls operation of the cable tester to make the desired measurements and display the results. The device is contained in a portable housing which may be hand held to facilitate convenient use of the device in difficult to access locations.

대표청구항 ▼

[ What is claimed is:] [1.] An apparatus for determining the location of a discontinuity in an electrical cable comprising:a) a variable frequency oscillator for applying a variable frequency oscillating test signal to a signal injection point at one end of an electrical cable under test;b) a refere

[ What is claimed is:] [1.] An apparatus for determining the location of a discontinuity in an electrical cable comprising:a) a variable frequency oscillator for applying a variable frequency oscillating test signal to a signal injection point at one end of an electrical cable under test;b) a reference resistor disposed between said oscillator and said signal injection point; andc) a microcontroller for controlling operation of said oscillator, said microcontroller including means for determining a frequency of said test signal at which an electrical impedance at said signal injection point between said oscillator and said cable is a minimum, and determining from said frequency, the distance from said injection point to a discontinuity in said cable, said microcontroller further including means for comparing a voltage magnitude at said signal injection point to a voltage magnitude at an oscillator side of said reference resistor, and determining that said discontinuity is: 1) an open circuit if said voltages are approximately equal to one another, and 2) a short circuit if said signal injection point voltage is approximately zero volts.