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Tester 301C Time Domain Reflectometer



 
 
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  #1  
Old December 23rd 03, 01:00 PM posted to uk.telecom
Ross
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Posts: 21
Default Tester 301C Time Domain Reflectometer

Hi All,

Does anyone else here use the Tester 301C Time Domain Reflectometer for
cable fault location. I have recently started to use one of these
instruments, having had to deal with several cable disconnection faults
which did not lend themselves to easy location using an Ohmmeter 18B. I have
the manual for the Tester 301C, and am happy with the general operation and
output analysis, indeed I have spent part of this afternnoon experimenting
with it, but I have two questions which someone here who has more experience
with the instrument might be able to answer.

1) The manual states that the instrument is calibrated for the velocity
factor/VOP of solid polythene dielectric, and will therefore induce an error
when used on other types of cable - e.g. PJ filled. Does anyone have any
knowledge of the amount of error to be expected, or even better, does anyone
have any correction tables?

2) The manual states, as is sensible with any test instrument, to ensure
that there are no hazardous voltages present on the pair under test. Note
the use of the word hazardous. In the telecommunications context, I would
assume that hazardous voltages are those which exceed the normal exchange
battery voltage (~50V dc) or those ac voltages arising from mains
contacts/leakage. Is it possible to use the Tester 301C on a live line, or
must the exchange battery always be disconnected at the frame?

Many thanks in advance,

Best Regards,

Ross


  #2  
Old December 23rd 03, 10:00 PM posted to uk.telecom
Zomaar
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Posts: 11
Default Tester 301C Time Domain Reflectometer


"Ross" wrote in message
.. .
Hi All,

Does anyone else here use the Tester 301C Time Domain Reflectometer for
cable fault location. I have recently started to use one of these
instruments, having had to deal with several cable disconnection faults
which did not lend themselves to easy location using an Ohmmeter 18B. I

have
the manual for the Tester 301C, and am happy with the general operation

and
output analysis, indeed I have spent part of this afternnoon experimenting
with it, but I have two questions which someone here who has more

experience
with the instrument might be able to answer.

1) The manual states that the instrument is calibrated for the velocity
factor/VOP of solid polythene dielectric, and will therefore induce an

error
when used on other types of cable - e.g. PJ filled. Does anyone have any
knowledge of the amount of error to be expected, or even better, does

anyone
have any correction tables?


I use the mole every day on PJ cables, no problems for the last 15 years...


2) The manual states, as is sensible with any test instrument, to ensure
that there are no hazardous voltages present on the pair under test. Note
the use of the word hazardous. In the telecommunications context, I would
assume that hazardous voltages are those which exceed the normal exchange
battery voltage (~50V dc) or those ac voltages arising from mains
contacts/leakage. Is it possible to use the Tester 301C on a live line, or
must the exchange battery always be disconnected at the frame?


It is almost always used with voltage on 1 or both legs - in fact, you need
to test towards a live line to find high resistance disconnection (noise)
faults on a PSTN line. Testing towards ISDN conditions can give a weird
result sometimes...

HTH, Ali


  #3  
Old December 24th 03, 01:04 PM posted to uk.telecom
Ross
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Posts: 21
Default Tester 301C Time Domain Reflectometer

Cheers Ali,

I use the mole every day on PJ cables, no problems for the last 15

years...

Why do you call it 'The Mole" ? )


It is almost always used with voltage on 1 or both legs - in fact, you

need
to test towards a live line to find high resistance disconnection (noise)
faults on a PSTN line. Testing towards ISDN conditions can give a weird
result sometimes...


Thats good......I've been proceeding with caution, as I've used a few other
TDRs before that could not tolerate any sort of voltage across the
measurment terminals.

Cheers,

Ross


  #4  
Old December 30th 03, 10:58 PM posted to uk.telecom
Michael Jackson
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Posts: 6
Default Tester 301C Time Domain Reflectometer


"Ross" wrote in message
.. .
"Why do you call it 'The Mole" ? )"

It goes underground :-) - as a rule anyone who calls it a
Tester 301C Time Domain Reflectometer (1) no way works for BT (2) would get
laughed out of the Exchange Automatic System X.


  #5  
Old December 31st 03, 04:27 PM posted to uk.telecom
Ross
external usenet poster
 
Posts: 21
Default Tester 301C Time Domain Reflectometer


Anyone who calls it a Tester 301C Time Domain Reflectometer (1) no way

works for BT

You might be right there, and I might be all the happier for it! From what I
hear and witness of the general working conditions for BT Engineering staff
these days (and no doubt other departments) I wouldn't fancy working for
them! I feel sorry for the guys out there who are sent on job without the
correct training / correct equipment / adequate assistance and are told to
'get the job done' regardless.

(2) would get laughed out of the Exchange Automatic System X.


Why?

Cheers,

Ross




  #6  
Old December 31st 03, 06:33 PM posted to uk.telecom
Kráftéé
external usenet poster
 
Posts: 8
Default Tester 301C Time Domain Reflectometer

Ross wrote:
Anyone who calls it a Tester 301C Time Domain Reflectometer (1)
no way works for BT


You might be right there, and I might be all the happier for it!
From what I hear and witness of the general working conditions for
BT Engineering staff these days (and no doubt other departments) I
wouldn't fancy working for them! I feel sorry for the guys out
there who are sent on job without the correct training / correct
equipment / adequate assistance and are told to 'get the job done'
regardless.


You forgot.....it's got to be done to a fairly high standard as well, any
old bodge isn't good enough it's got to be good quality bodging.. ;-)
Problems aren't made any better when the powers that be change fundimental
bits of the kit used & then they find that the new kit isn't compatable (I
kid you not)...


(2) would get laughed out of the Exchange Automatic System X.


Why?


Actually it wouldn't happen as there'd be nobody there...


 




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