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Author Topic: TDR Measuring Equipment  (Read 14350 times)

Darrenhorsfield

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Re: TDR Measuring Equipment
« Reply #15 on: October 06, 2018, 09:09:54 AM »

Do you know how far the JDSU SMART HOME V3 meter can test opens copper pairs
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Black Sheep

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Re: TDR Measuring Equipment
« Reply #16 on: October 06, 2018, 12:46:07 PM »

Do you know how far the JDSU SMART HOME V3 meter can test opens copper pairs

Good question and one I can't give a definitive answer to, I'm afraid.

The reason being that I've never had to test the TDR function of the JDSU to its upper limits .... there may well be some spec/doc giving that kind of information ??

The one thing I can say is that the further up the TDR spectrum you go (ie: the longer the length you are viewing), the trace becomes far, far more erratic and harder to 'read'. Simple poundage changes can appear as 'Full on disconnections', unless the operator turns the automatic gain function down.

On my JDSU (not certain what version it is, tbh ??) .... the TDR screen has viewing ranges from 'X-Short' (at zero metres +), through 'short', medium, long to the final viewing screen of 'extend'. The highest figure the TDR cursor can move to at that range is 13,320mtrs ...... so I suppose that is the answer to the question in theoretical terms, but I much prefer practical experience when giving a reply.  :)
 
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Darrenhorsfield

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Re: TDR Measuring Equipment
« Reply #17 on: October 06, 2018, 01:46:37 PM »

Just had a look at the V3 spec and it stated can read opens to 9999 meters, I think this is a bit low to use when testing field telephone pairs to get a path to the exchange. May have to consider alternative meter.
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Black Sheep

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Re: TDR Measuring Equipment
« Reply #18 on: October 06, 2018, 02:17:09 PM »

Where are you working ..... the wilds of Scotland, or Wales perhaps ..... there's not that many lines with the kind of distances you are talking about, in the rest of the UK ??
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Weaver

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Re: TDR Measuring Equipment
« Reply #19 on: October 06, 2018, 11:04:12 PM »

Not many lines even round here that are 10km
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Starman

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Re: TDR Measuring Equipment
« Reply #20 on: October 07, 2018, 01:18:06 PM »

I have an ONC in Electronic Engineering (20yrs ago though), but my particular 'final project' was just an alarm system, and was relatively easy to build.

Ironically I am currently in my final year for my BTEC Level 3 [Modern day ONC with progressing to my HNC next year] in Electronic and Electrical Engineering and I am building something very similar - I guess some things never change ;)

We also use TDR for finding open circuit/earth faults within the electrical distribution sector. I suspect our equipment (normally a Bicotest T631] is rather outdated and some models do struggle with near faults <6M. So we generally give the service a 'Cosser' trace and if you don't see something over 10M its normal practice to excavate and open and test the service on the customers boundary line and confirm a fault direction. You typically then  depending on length of route trace back in the needed direction and locate the fault.

We do have a large "test van" which used on higher voltage faults (11kV+) this isn't generally used on the LV side because you require the cable to be completely isolated from customers to avoid damaging equipment after the TDR is used its normal to "bang" the fault which injects a high voltage but low current which causes the fault to "thump" in the footway so you have a rough distance to fault you know the approximate cable route so you then walk to the area and either use a acoustic listener or sometimes your own ears and feet.
« Last Edit: October 07, 2018, 04:45:24 PM by Starman »
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Black Sheep

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Re: TDR Measuring Equipment
« Reply #21 on: October 07, 2018, 04:12:26 PM »

Hi Starman .... yeah, also our modern technology struggles with 'near-end' faults (ie: identifying the distance) as much as it does 'far end' faults.

For near-end faulting, we tend to employ a 'known resistance' dummy load (ie: lets say a 20mtr length of cable, or the equivalent resistor) and when the actual fault is applied to the TDR, we can subtract the 'known value' and home in on the issue.

After 30+yrs of faulting, I still don't know why our testers struggle with 'near end' HR's/Open circuits  ......... they just do.  ::) :)
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Darrenhorsfield

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Re: TDR Measuring Equipment
« Reply #22 on: October 07, 2018, 09:08:24 PM »

I meant 999 meters. I am correct that t he JDSU S-Home V3 can only measure opens up to 999? Does anyone know a cheap alternative.
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Weaver

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Re: TDR Measuring Equipment
« Reply #23 on: October 08, 2018, 12:19:44 AM »

My neighbours’ phone lines are between 7300 and 8670m long.
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Black Sheep

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Re: TDR Measuring Equipment
« Reply #24 on: October 08, 2018, 07:32:41 AM »

I meant 999 meters. I am correct that t he JDSU S-Home V3 can only measure opens up to 999? Does anyone know a cheap alternative.

Just realised our kits are JDSU HST 3000 ............ but may be a bit out of your price range ??
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Darrenhorsfield

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Re: TDR Measuring Equipment
« Reply #25 on: October 08, 2018, 06:49:13 PM »

So your JDSU V3 HOME can test over 5000 meters?
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Black Sheep

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Re: TDR Measuring Equipment
« Reply #26 on: October 08, 2018, 07:39:53 PM »

So your JDSU V3 HOME can test over 5000 meters?

I don't have a JDSU V3 Home, I have a JDSU HST 3000 ..... and I don't know for certain its practical upper limits for TDR (see above posts), but I would put my wage on it performing beyond 5K.
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Weaver

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Re: TDR Measuring Equipment
« Reply #27 on: October 08, 2018, 11:29:55 PM »

Well, my own lines are 7300m.
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Darrenhorsfield

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Re: TDR Measuring Equipment
« Reply #28 on: October 10, 2018, 07:12:20 PM »

Well, my own lines are 7300m.
Are you using the JDSU V3 to measure that.
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j0hn

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Re: TDR Measuring Equipment
« Reply #29 on: October 10, 2018, 07:28:16 PM »

Are you using the JDSU V3 to measure that.

BlackSheep pointed out that he uses a JDSU HST 3000.
If that is the same thing as a JDSU V3 I've no idea.

I'm not aware of any other members who would be using that kind of kit regularly, and on such long circuit lengths.
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