Program to Estimate Cat 5 Cable Length
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Posted by Dan P on October 1, 2004, 4:52 pm
Please log in for more thread options I just have a quick question. Has someone written a program that measures, say, the ping between a computer and a router and takes that and estimates the length of a network cable? I was just wondering if something like this was out there. Thanks, Dan P | |||||||||||||||||||||||||||||||
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Posted by James Knott on October 2, 2004, 1:42 am
Please log in for more thread options Not likely. The total transit time of the ping and echo over the wire is less than 0.5 uS. The time it takes the computers to transmit, handle and receive the ping or echo is far greater than that. However, there is an instrument, that can not only measure cable length, it can also show faults along that length. This device is called a "time domain reflectometer" (TDR). N.B. The velocity of a signal in a vacuum is about 300,000,000 metres per second. The maximum twisted pair ethernet cable is 100 M. Allowing for 200 M total echo distance and allowing for velocity factor, brings us to about 300 nS or 0.3 uS total transit time for ping and echo. Also, at 100 Mb, a ping will be more than 5 uS long. -- (This space intentionally left blank) | |||||||||||||||||||||||||||||||
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Posted by Dmitri(Cabling-Design.com on October 4, 2004, 5:44 pm
Please log in for more thread options James Knott wrote:
> Dan P wrote:
> Not likely. The total transit time of the ping and echo over the wire
> is > less than 0.5 uS. The time it takes the computers to transmit, handle > and > receive the ping or echo is far greater than that. However, there is > an > instrument, that can not only measure cable length, it can also show > faults > along that length. This device is called a "time domain > reflectometer" (TDR). > N.B. The velocity of a signal in a vacuum is about 300,000,000 metres
> per > second. The maximum twisted pair ethernet cable is 100 M. Allowing > for > 200 M total echo distance and allowing for velocity factor, brings us > to > about 300 nS or 0.3 uS total transit time for ping and echo. Also, at > 100 > Mb, a ping will be more than 5 uS long. NVP (Nominal Velocity of Propagation) in a UTP cable would be around 0.67 times velocity in vacuum. That makes it "only" about 200,000,000 meters per second ;-) Really does not change much about the particular matter though, so agree with everything else. -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 4653 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||
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Posted by Watson A.Name - \"Watt Sun, th on October 2, 2004, 11:31 pm
Please log in for more thread options
> Hello all,
> I just have a quick question. Has someone written a program that > measures, say, the ping between a computer and a router and takes that > and estimates the length of a network cable? I was just wondering if > something like this was out there. > > Thanks, > Dan P The time would be much, much too small in comparison to the electronics. | |||||||||||||||||||||||||||||||
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Posted by Dmitri(Cabling-Design.com on October 4, 2004, 5:35 pm
Please log in for more thread options Dan P wrote:
> Hello all,
> I just have a quick question. Has someone written a program that > measures, say, the ping between a computer and a router and takes that > and estimates the length of a network cable? I was just wondering if > something like this was out there. > Thanks,
> Dan P It just doesn't make sense: to accommodate for all possible combinations of lengths that a pair of Ethernet devices may encounter (from 0 to 100 meters), the devices are designed to hold the data received in the buffer memory for at least the duration of the longest trip - 100 meters. Therefore, any measurement you might be able to take this way (without arguing whether it's even possible to measure such tiny time interval with devices not specifically designed for that) will always show one length - 100 meters (295 ft) -- Dmitri Abaimov, RCDD http://www.cabling-design.com Cabling Forum, color codes, pinouts and other useful resources for premises cabling users and pros http://www.cabling-design.com/homecabling Residential Cabling Guide ------------------------------------- ##-----------------------------------------------## Article posted with Cabling-Design.com Newsgroup Archive http://www.cabling-design.com/forums no-spam read and post WWW interface to your favorite newsgroup - comp.dcom.cabling - 4651 messages and counting! ##-----------------------------------------------## | |||||||||||||||||||||||||||||||
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> I just have a quick question. Has someone written a program that
> measures, say, the ping between a computer and a router and takes that
> and estimates the length of a network cable? I was just wondering if
> something like this was out there.