L/R Ratio for the cable

For non (and) coaxial cables this ratio does not indicate inductance but rather the resistance per unit length.,"L" in this case. For power cable ,DC to 1000Hz, the "L" (Inductive) component usually plays no important role. "Z" or the impedance is also measured in "R" units

Wangito

You can think of a cable being constructed of a series of resistors inductors and capacitors arranged like this.

Which is actually a whole stack of band pass filters wired up in series. The response of each of these band pass filters it effected by the various values of the components and these are controlled by the specifications of the cable.

Understanding what goes on here is to complex for posting here but I suggest you read up on Transmission Line Theory. It's a bit heavy going but if you work through this it will give you a good understanding of what is going on in any cable from the coax that feeds your TV to the power lines that carry 135 KV

the L/R ratio is in time units. the meaning is the time constant of the current (rise time) within the cable. this value is very important since it can be used for fuse type selection.

It would indicate the frequency response of the cable, and therefore its suitability for transmission at the chosen signal frequency.

Hi Siddharth;

Cable L/R ratio is a critical parameter to determine if an instrument and its cabling could be used safely in a hazardous location. Inductors, including cabling, will generate a voltage spike when current flow is stopped (switches, relays and loses terminal connections). If there is enough stored energy in the inductor, the voltage spike will arch over the break and ignite the gases in the hazardous area causing an explosion. The high resistance in low L/R ratios cable will suppress the generation of dangerous arching. The low L/R cables have higher IR losses and limit the system cable runs lengths.

More information can be found in ISA-RP12.6 - Wiring Practices for Hazardous Area Instrumentation

can you please ellobrate your reply.

Intrinsic safety - Wikipedia

Instrumentation cable L/R ratio is critical parameter for Hazardous areas only?

What about non-hazardous areas?

<...What about non-hazardous areas?...>

The parameter is rarely of interest except in the transmission of high frequency signals, where it can be used to determine the loss of signal per unit length.

Please do not get involved with selecting cables for use on circuits in hazardous areas that are intended to be intrinsically safe without having completed appropriate training beforehand.