Instrument and method for testing local area network cables

In a LAN cable test instrument, a method for evaluating near-end cross-talk between first and second twisted-wire pairs in a LAN cable, comprising:

• (a) measuring capacitances between a first wire of said first twisted-wire pair and one wire of said second twisted-wire pair and between a second wire of said first twisted-wire pair and one wire of said second twisted-wire pair within said LAN cable to produce first and second capacitance measurement values;
• (b) measuring capacitances between a first wire of said first twisted-wire pair and another wire of said second twisted-wire pair and between a second wire of said first twisted-wire pair and another wire of said second twisted-wire pair within said LAN cable to produce third and fourth capacitance measurement values;
• (c) calculating a first capacitance difference value between said first and second measurement values;
• (d) calculating a second capacitance difference value between said third and fourth measurement values;
• (e) comparing said first and second capacitance difference values to a predetermined figure of merit correlated to an acceptable level of near-end cross-talk;
• and
• (f) generating an error signal if at least one of said first and said second capacitance difference values exceeds said predetermined figure of merit.

In a LAN cable test instrument, a method for evaluating near-end cross-talk between a twisted-wire pair and a conductor in a LAN cable, comprising:

• (a) measuring capacitances between a first wire of said first twisted-wire pair and said conductor and between a second wire of said first twisted-wire pair and said conductor to produce first and second capacitance measurement values;
• (b) calculating a capacitance difference value between said first and second measurement values;
• (c) comparing said capacitance difference value to a predetermined figure of merit correlated to an acceptable level of near-end cross-talk;
• and
• (f) generating an error signal if said capacitance difference value exceeds said predetermined figure of merit.