Cable - Capacitance, Resistance,inductance

Discussion in 'General Electronics Chat' started by vineo763, Oct 2, 2006.

  1. vineo763

    Thread Starter Member

    Aug 13, 2006
    12
    0
    Cables often have specifications such as resistance, inductance, and capacitance. Does anyone know how I should measure these specifications? Is it as simple as using a multimeter?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,140
    1,789
    Cable parameters cannot in general be measured with a multimeter. Since they are distributed paramaters capacitance, inductance and resistance are usually measured per unit of length. DC resistance of a conductor can be measured with a multimeter but that measurement is of little practical value since we are generally more interested in the cable parameters as a function of frequency.

    The top of the line instrument to measure cable parameters is a network analyzer; it is a pricey bit of gear. There are also a variety of other instruments that take more work but yield similar results.
     
  3. bhavesh96el

    Member

    Apr 24, 2006
    11
    0
    Papabravo.. I did understand what you said that cable parameter is function of frequency.

    But i didn't understand is how can we measure the capacitance and inductance of cable using network analyser ?

    From frequency response impedance Z can be derived

    but then how can we derive capacitance and inductance?

    I guess we can say the attenuation dB/m using Network Analyser.

    REgards
     
  4. bhavesh96el

    Member

    Apr 24, 2006
    11
    0
    Papabravo,

    I understood that cable parameter is frequency dependant.

    Frequency respone,obtained from Network Anaylser, can be used to derive impdance (Z) of the cable.

    However, I can not figure out how can we obtain Capacitance and Inductance from it ?

    Regards
    Bhavesh
     
  5. CATV

    Member

    Apr 17, 2007
    11
    0
    Using a network analyzer, you can get the output presented in a Smith Chart format which will show you the capacitaive and inductive compnents of the transmission line. Call Comm/Scope in Hicory NC and they will give you more details.
     
  6. Tube Tech

    Active Member

    Jan 11, 2007
    46
    0
    With a tape measure. The paramaters you describe are listed in picofarads per 100 feet, et cetera. Measure and calculate.
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    With good cable, we don't need a tape measure. Footage should be printed on the cable every one or two feet.

    Network analysers are expenisve to buy, but there are many places where such can be rented.
     
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