Portable Earth unit / vitual earth

[mckayb659]

Hi every one
I'm a telephone engineer and work out on the road fixing peoples phone. The testing equipment i use is the JDSU. I work on 50 volt circuits which is the norm for telephones. Alot of the tests i need to do i have to plug my meter in to an earth point. Not a problem in peoples houses an not a problem when i'm near peoples gardens as i can just plug an spike in to someones grass to get a good earth. There are times when neither is possible. Is there a unit i can build or purchase that would act as a portable earth or ground so if im up a telegraph pole i can get an earth point really easily to run my tester

Many thanks
Brian

 

[alec_t]

Welcome to the forum!
Interesting problem, but if a voltage you're measuring is referenced to true earth IMO your meter will also have to be referenced to true earth. So even if you could create a virtual earth, that in turn would have to be referenced to true earth and would leave you with the same problem . I'm stumped, but others may have useful suggestions.

 

[Nigel Goodwin]

No, because you're measuring (as always) in reference to 'something' - in your case the reference is earth, a virtual earth would be no help at all.

All you can do is run a wire up the pole from an earth spike.

 

[mckayb659]

Thats really helpful many thanks that's save me a lot of time on wild good chases. Its a shame really cos it would be a pretty cool device.

 

[Nigel Goodwin]

If it was possible your test equipment would have incorporated it decades ago.

 

[mckayb659]

No. I definitely need to connect to ground/earth to run certain tests. My tester is very new JDSU. I have managed to find an earth on a tree branch when i was up one telegraph pole a couple of months ago. Once i broke through the bark that is. Sometimes when working in a front garden that has concrete all over it, i just cant get an earth without causing trip hazards to the general public.

 

[mckayb659]

My real problem is i just dont know about electronics what i mean to say is I really have no clue which is why i have come to you kind chaps. Im doing a little research on this and have found some dummy info which is pretty cool, but im not quite understanding why it cant be done electronically. I have seen some engineers throw the earth leed in the bottom of a chamber thats got about three inches of water in the bottom while they are working on a telephone line. You may have seen these telecom boxes on the pavement, might be one outside your house.

 

[Nigel Goodwin]

My real problem is i just dont know about electronics what i mean to say is I really have no clue which is why i have come to you kind chaps. Im doing a little research on this and have found some dummy info which is pretty cool, but im not quite understanding why it cant be done electronically. I have seen some engineers throw the earth leed in the bottom of a chamber thats got about three inches of water in the bottom while they are working on a telephone line. You may have seen these telecom boxes on the pavement, might be one outside your house.

Not on my street

But I know what you mean.

It IS done electronically, that's what the wire to ground is for.

What you're wishing for is 'wirelessly'.

However - it's a VERY simple and easy to understand principle.

Imagine a battery, a bulb, and a couple pieces of wire - connect them all in a circuit and the bulb lights up, disconnect one of the wires and the bulb no longer lights.

Your required connection to earth is essentially one of those wires.

 

[mckayb659]

Well that was simple. The penny has dropped. that was the missing link. Thats the pricniple i use when looking for voltage on hundreds of lines. One leg on my voltage meter i put to earth and the other leg on my voltage meter goes to one of the phone wires when i get a voltage i know its a working line.
So what if i connected the earth leg to a dead battery, or a large transformer on the input. Would that absorb the voltage like just shoving the end on an earth spike? Or should i just stick to fixing phone lines and leave the electronics to you guys!!. Thanks for all your patients and giving me a very warm welcome to this site!!

 

[Nigel Goodwin]

Well that was simple. The penny has dropped. that was the missing link. Thats the pricniple i use when looking for voltage on hundreds of lines. One leg on my voltage meter i put to earth and the other leg on my voltage meter goes to one of the phone wires when i get a voltage i know its a working line.
So what if i connected the earth leg to a dead battery, or a large transformer on the input. Would that absorb the voltage like just shoving the end on an earth spike? Or should i just stick to fixing phone lines and leave the electronics to you guys!!. Thanks for all your patients and giving me a very warm welcome to this site!!

You need to complete the circuit, to do that you must have a connection to ground (as ground is one of the connections) - it's nothing to do with 'absorbing the voltage' (which is nonsense anyway).

Have you ever seen the old morse code telegraph systems?, such as used in the Wild West - similar principle, a single wire carried on poles over ground, with the return been made via the earth. Just as with the light bulb example above if the wire is broken it can't work, and if the earth connection is broken it can't work either.

 

[JMW]

What does your company suggest? I'm certain you're not the first with this issue.
Oh and please stick with the forum. Most of my career was in radio telecommunications, telephone lines were a bane to my existence. A telephone tech with electronics backing would have been wonderful.

 

[Mosaic]

Walk with a cordless drill and a concrete 6" bit.

 

[alec_t]

I have managed to find an earth on a tree branch when i was up one telegraph pole a couple of months ago. Once i broke through the bark that is.

Nice improvisation. I guess a tree makes a pretty good ground rod (well, at least it does for lightning). Wonder what the sap resistivity is?