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Old 18th Jul 2011, 7:06 am   #1
noble kiwi
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Default GPO Portable Volt Meters

I have in my collection two DC volt meters both of which appear to be designed specifically for use by telephone technicians. One is manufactured by Everett Edgcumbe, London and the other by AWA in Australia. They are both of a similar design, which is different from the the normal concept of portable instruments, in that they are of a cubicle shape. Binding posts and controls are on the top side with the scale on the front. A leather case with shoulder strap is provided and this opens top and front so that the meter can be used without removal.

I would be interested to learn as to whether this is a style was originated by the British GPO and if so the practical reasons for its adoption. The New Zealand Govt. P&T department largely followed British practices and specifications, as did Australia. I will be pleased to provide further details if anyone is interested and any replies will be sincerely appreciated.

Trevor.
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Old 18th Jul 2011, 12:37 pm   #2
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Default Re: GPO Portable Volt Meters

Pictures?
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Old 19th Jul 2011, 3:32 am   #3
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Default Re: GPO Portable Volt Meters

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Originally Posted by noble kiwi View Post
I will be pleased to provide further details if anyone is interested and any replies will be sincerely appreciated.
On confirmation that there is worthwhile interest in the subject, I will be happy to take the time necessary to include several photos.

Sincerely, Trevor.
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Old 19th Jul 2011, 8:40 am   #4
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Default Re: GPO Portable Volt Meters

Trevor,I think this might be what you are describing.
Known as a detector No4 in GPO/Post Office Telephones parlance.
This one was in the van tool kit I took over in 1966 and is dated '55 (I never used it).
The shunts and series resistances extend the ranges and normally live in the smaller leather box.
I remember as an apprentice working with a cable gang one being used to identify cable pairs.
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Old 19th Jul 2011, 5:28 pm   #5
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Default Re: GPO Portable Volt Meters

Thank you Dave,

What you have illustrated is similar to the AWA meter I have. It is the concept of the physical design which intrigues me, as it appears the terminals and controls are very awkward to use. There must be some logic behind the box shaped design concerned with its particular use, but it is beyond me. The limited and very specific ranges provided must also indicate that it was intended for a rather special application.

The plot thickens and I am now even more interested, as it is clear that the design was quite universal and supplied by more than one manufacturer, probably to a BPO specification. I will photograph mine and post images ASAP.

Thanks again, Trevor.
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Old 19th Jul 2011, 8:10 pm   #6
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Default Re: GPO Portable Volt Meters

There should be a spike, screwed into the bottom, which was taken out and screwed to the under side, so that when on the pole, the engineer could connect to the earth wire ( which ran up the pole ) by stabbing(?) the earth wire. Small size, to get between the parallel wires. Cliff.
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Old 19th Jul 2011, 9:34 pm   #7
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Default Re: GPO Portable Volt Meters

When I joined Post Office Telephones in 1967 many engineers liked to use the Detector No.4 in preference to a multimeter. It was always called a "clock" though.
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Old 20th Jul 2011, 1:27 am   #8
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Default Re: GPO Portable Volt Meters

Kia ora all and special thanks,

I am now able to apply a name, i.e. --- Detector No. 4. Yes it has the spike. I had started a complete description so will continue to post same as follows:-

Voltage. Two ranges. 0 - 5 & 0 - 55 volts DC.
Current. Two ranges. 0 - 50 mA & 0 - 500 mA.
If required the meter can be connected to register 0 - 0.1 volt or 0 - 1O mA.

Moving coil portable instrument, manufactured by AWA. Model 55. Complies BS 89 ind. Serial No. 2927827. Dimensions overall, width 90 mm, height 100, depth 55. Metal enclosure, black crackle finish with bakelite top section. Complete with test leads and also an interesting extra test prod, which is screwed into the base for use when there is nowhere to rest the meter. It is obviously designed for a specific purpose. Very robust design with test leads connected via four binding posts, which together with a rotary switch provide range selection. Provision is made for external shunts. A photo engraved brass instruction plate attached to the rear.

The original leather case has endured much handling and shows that the meter has withstood a lot of use and confirms its quality. Accuracy has been proven as remaining exact, partly no doubt due to the movement being of relatively low resistance and therefore quite robust.

I like the way a collection can trace a history of technical development and in this regard the British GPO is of special interest. It would appear that this meter traces the development of the multi meter, in that it was a probably an ongoing modification of an existing style of single range instrument in use, i.e. a simple cubic construction and the minimum necessary to contain the movement.

The original concept has obviously survived and remained in use time tested. The fact that mine appears to have been manufactured in Australia is interesting. Can anyone advise regarding the date when and how the design originated?

P.S. I think I have now latched on to the advantages of the design, in that its cubic and compact shape was an advantage when up/on a pole, thus resulting in a long and useful life.

Trevor.

Last edited by noble kiwi; 20th Jul 2011 at 1:47 am.
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Old 20th Jul 2011, 7:00 am   #9
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Default Re: GPO Portable Volt Meters

With regard to my previous posts, I now include photos of the two meters I have been referring to.

The first two show the Detector No. 4 and the others the Everett Edgcumbe meter, which I think must have been intended for telephone battery cell testing. Note the selector switch lever protruding from a slot behind and between the terminals and which brings into circuit a 2 Ohm shunt as a load across the battery under test. Strangely the switch has a centre position which has no actual function.

This latter meter and its leather case, appears to have had hardly any use, possibly due to its specialised function meaning that it was not often carried and on hand.

I appreciate that this stuff must be boring and old hat to many, but not so to me.

Trevor.
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Last edited by noble kiwi; 20th Jul 2011 at 7:14 am.
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Old 20th Jul 2011, 10:33 am   #10
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Default Re: GPO Portable Volt Meters

Quote:
There should be a spike, screwed into the bottom, which was taken out and screwed to the under side, so that when on the pole, the engineer could connect to the earth wire ( which ran up the pole ) by stabbing(?) the earth wire. Small size, to get between the parallel wires. Cliff.
Hi Cliff

I'm told that it is, literally an earth spike. Ramming into the ground for measuring lines to earth, for the use of.
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Old 20th Jul 2011, 11:42 am   #11
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Default Re: GPO Portable Volt Meters

I am literally sure that you have been wrongly told and Cliff is very likely correct.
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Old 20th Jul 2011, 2:03 pm   #12
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Default Re: GPO Portable Volt Meters

Faultsmen often need to measure voltages between each leg of a telephone line to earth, as a low path to earth on the "battery" side can cause all sorts of problems such as noise and overhearing. When I was "up the poles and down the holes" back in the mid '90's I used to use the modern equivalent of this, the Tester 9083, which was a special multimeter with a 3rd terminal to earth which enabled, amongst other things easy measurement of A leg and B leg to earth.
No spike though, just clip leads!

I think the shunts were for use by exchange staff for measuring exchange battery voltages/currents etc.

I have a GEC one of these but although working it has no glass in. It is of use on car electrics but that's about all.
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Old 20th Jul 2011, 11:09 pm   #13
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Default Re: GPO Portable Volt Meters

Hello All, Thanks Tim for your support. As it was a long time ago I think Tim may be correct but I now seem to remember a spike fitted on a strangly shaped plate perhaps in the shape of a capital G. Again seeing it close up ( to understand it better ) is not an option now. I also used the 9083/2 with its pair reversing switch and then the meter multy range 12 series. These new digital meters with all the dancing digits is no advantage over a moving pointer. Cliff.
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Old 21st Jul 2011, 1:42 am   #14
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Default Re: GPO Portable Volt Meters

Kia ora Cliff,

The included prod screw fitting on the bottom of my meter is labelled “spike + “ and when removed and refitted the spike extends only 20 mm. The concept of “Ramming into the ground for measuring lines to earth, for the use of.” is beyond logical reasoning. The short “spike” is sharpened to a point and is perfect for “stabbing” into an earthwire or whatever. This was my immediate assumption when I first examined this feature and I am sure is correct.

I certainly agree that a pointer can provide information not available from “dancing digits”. I like that description! N.B. In spite of a lot of dancing early on, in the end the time honoured hands and pretty face hold the prize for the clocks and watches ballet. LOL

Cheers, Trevor.
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Old 21st Jul 2011, 3:33 pm   #15
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Default Re: GPO Portable Volt Meters

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The included prod screw fitting on the bottom of my meter is labelled “spike + “ and when removed and refitted the spike extends only 20 mm. The concept of “Ramming into the ground for measuring lines to earth, for the use of.” is beyond logical reasoning.
Fair enough!
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Old 22nd Jul 2011, 6:29 am   #16
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Default Re: GPO Portable Volt Meters

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Originally Posted by noble kiwi View Post
Can anyone advise regarding the date when and how the design originated?
This item appears to have been in regular use worldwide for a very long period and therefore it surely represents a significant GPO design. Not quite alongside the BPO 3000 relay, but never the less.

I would specially appreciate information confirming its history.

Sincerely, Trevor.
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Old 22nd Jul 2011, 6:44 am   #17
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Default Re: GPO Portable Volt Meters

Quote:
Originally Posted by noble kiwi View Post
--------- Everett Edgcumbe meter, which I think must have been intended for telephone battery cell testing. --------

I appreciate that this stuff must be boring and old hat to many, but not so to me.
Please refer to my previous post #9 and photos. Has anyone run across this particular meter and is it a GPO specified item, or peculiar to the New Zealand Post Office?

Sincere thanks in anticipation, Trevor.

Last edited by noble kiwi; 22nd Jul 2011 at 6:48 am. Reason: Ref. added.
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Old 22nd Jul 2011, 8:19 am   #18
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Default Re: GPO Portable Volt Meters

Hi again Trevor..when I was on Post Office Telephones training courses in the late 60s, at Bletchley Park, we occassionally had British Rail telecoms staff training with us. They had similar testers and tools to us but without the GPO logo. This may be another "line" (pardon the pun) of investigation.
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Old 22nd Jul 2011, 1:42 pm   #19
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Default Re: GPO Portable Volt Meters

When I was a y2yc in training late 40's the no 4 was the only test instrument for the staff, one member might have charge of an Avo. The earth spike when plugged in became a prod for testing purposes being connected to the upper positive terminal(the 22 & 40 volt exchanges being + earth.) Finding the no4 limited I decided to improve my testing facilities.

Later when I became an internal mtce. engineer I built a copy of the exchange test desk ( thanks to J. Atkinsons book, "Telephony" which I still have) which enabled me to be self contained, only the final test for the whole system from the test desk was required, Alas when I left I had to leave the tester behind as it used GPO items.

This led on to an interest in radio, the TRF (many a shock) the superhet & finally to the love of my life the tape recorder.

I still have my no. 4 dated 47.

Colin,.
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Old 3rd Nov 2011, 9:16 pm   #20
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Default Re: GPO Portable Volt Meters

I've been trying to find out what one of these No4 meters was for years. I bought one for two and sixpence 60 years ago as a schoolboy interested in electronics , I couldn't afford an AVO so I made shunts and series bobbins to up the range to 5A and 260V, eventually I was able to buy an Avominor. Still have the No4 but the wirewound series resistor for 50V is open circuit.
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