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Old 14th Jul 2008, 12:23 pm   #301
Oldtestgear
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Default Re: AVO Multimeter survey

Hi Everyone,
Thought that I would put in an appearance here!
My AVO is a type 5 Serial no: 2671-v-251. At the risk of showing just how ignorant I am about it, I think it is an exRAF model (in very faded RAF blue under the rust and general crud it has accumulated over the decades) with a plastic case marked "AVO"
It still works and is fairly accurate on the Volts ranges. Ohms and current? No idea as I have not tried. Are batteries still available?
Bought for £2 when I bought a lot of other kit in December 2006 and has sat under my bench since except for a quick test.
Lovely old instrument and so well built!
Phil.
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Old 14th Jul 2008, 1:34 pm   #302
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Default Re: AVO Multimeter survey

Yes, batteries are still available:
a 1.5 volt U2 (or whatever it's called in "today's money")
and a 15 volt BLR121, or equivalent, still available from Maplin.
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Old 14th Jul 2008, 1:57 pm   #303
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Default Re: AVO Multimeter survey

Sorry, Phil, I may have jumped the gun, there !

You said a Type 5, and I immediately assumed a Model 8 Mark V,
but the "rust and crud" and "RAF blue" suggests that it's an older Model.
The serial number is inconclusive.

AVO never produced a Type 5 (and their "Model 5" was never identified by number, but as a "36 Range Universal"). The battery for these has long since disappeared, but there are non-destructive "fixes" which could get it working.

If you can describe the instrument (scale, knobs, ranges etc, or put up a picture, I should be able to identify it.
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Old 14th Jul 2008, 7:21 pm   #304
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Default Re: AVO Multimeter survey

Ok,
Here goes!
On the meter is:
Type V (LHS) No 2671-V-251 (RHS)
The case is metal and the instruction label address is:
The Automatic Coil Winder And Electrical Equipment Co Ltd
Winder House, Douglas Street,London S.W.1

There is an earth point on the top front of the case.
Ranges are
9 off DC current 0.05 to 1000mA
3 off Ohms ranges (low, x1,x100)
5 off AC Volts (10/1000)
6off DC Volts (2.5/1000)
The carry case is a type of plastic covered cloth,with the AVO logo on the front.

So what is it?

Phil.
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Old 15th Jul 2008, 7:01 am   #305
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Default Re: AVO Multimeter survey

Hi There,
Avometers were popular in NZ too, I have one of the originals S.N.144 145
The brass plate on front states 'THE AVOMETER' MACADIES PATENT
Automatic Coil Winder and Electrical Equipment Co.Ltd.
Wellington House, Buckingham Gate London SW1
Patents granted or pending in principle countries
British Patent No.200977

Have a few over models too incl.
Universal 36 SN 66 5493
Avominor Universal U 100 689 347
DC Avominor 10447-24
model8 Mk1 panclimatic (ex Aust.Navy) 2xxxx-C-154
Avo 7 mkII 2xxx-A-462 ex NZPO.
Hope this of help for the list.
Not all of these in wkg order. Navy model 8 has low sensitivity and may need new movement.
Am at present looking for info on a Cossor scope CDU 130
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Old 15th Jul 2008, 9:36 am   #306
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Default Re: AVO Multimeter survey

Phil,

To be honest, I don't know. I think PMM will have to bale us out on this one.

From the ranges (which have a Model 8 "feel" to them, but aren't quite right) it sounds as if it may be one of the High Resistance models which preceeded the Model 8.
The date code in the serial number (Feb 1951, if it follows the format of the period) puts it about 3 months before the Model 8 was introduced.
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Old 15th Jul 2008, 8:21 pm   #307
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Default Re: AVO Multimeter survey

Arthur - just a few!! What else have you got?

It's just not possible to start the list of your collection with a more impressive entry - an original.

Do you know anything of its history? You will understand that there are not too many of these around so establishing a serial number pattern and hence the date is a bit uncertain. At a guess, I would say that it must have come fairly late in the production run between 1923/4 and 1927.

PMM
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Old 15th Jul 2008, 9:09 pm   #308
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Default Re: AVO Multimeter survey

Phil,

From your description, this is a panclimatic High Resistance Avometer - it should have "High Resistance Avometer" as the title marked on the instruction plate on the back. The other obvious distiguishing featute is the switch arrangement which is unlike any other mainstream Avometer. The LH switch will be marked "mA and (omega)" and the RH switch "VOLTS".

As SPCH states, this must have been one of the last of a fairly short production run as the Model 8 was introduced in May 1951.

My own example of this type is Serial No. 239-V-748 and there is a marking 10S/821 at the lower centre of the scale plate - an Air Ministry designation. The implication is that over 2000 of the type were made but as we have heard of so few there is, at present, no way of confirming this.

With reference to Mike's posting of the 7th July, I had assumed that these are the serial numbers of two separate meters, one with its serial number on the scale plate and the other with a self-adhesive label on the side - and repeated in the battery compartment. The first meter would be a Model 8 MK II and the second a Model 8 Mk V.

PMM.
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Old 16th Jul 2008, 12:03 pm   #309
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Default Re: AVO Multimeter survey

Quote:
Originally Posted by pmmunro View Post
Arthur - just a few!! What else have you got?
This one came from an auction (1989) of a deceased estate. retired sparky.
It is in pretty original condition. The meter face plate is cast alloy, I wonder if this was black originally, there are traces of black paint on it. Control panel and knobs are ebonite. About the only thing it has in common with the later AVO's is the arc scale. Have not seen another of these anywhere, or even a picture. were they widely advertised eg in Wireless World? I have a small collection of early multimeters incl. Weston, Ferranti, Triplett, Simpson, Hoyt & some Aussie models by Palec, Calstan and University.
Arthur
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Old 16th Jul 2008, 12:18 pm   #310
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Default Re: AVO Multimeter survey

Thanks, PMM, I knew you'd 'sort it'.

Sorry, Calum, it seems I misunderstood your post.
Don't know why, but what leapt out of the page at me was that you had ONE meter with TWO serial numbers ! Faced with such an unlikely - actually impossible - marriage, I did the dog-with-a-bone thing. Thanks for the inputs to the survey.

Thanks to everyone for keeping them coming.
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Old 16th Jul 2008, 4:27 pm   #311
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Default Re: AVO Multimeter survey

SUMMARY:

AVO 40, Ser. Number: 55547 40/2/75

SOME BLURB:

Following a nostalgia kick, I snapped up, online, an AVO 40 complete with leather case, prods, and clips. All in good condition and all ranges work fine - haven't tried 'Ohms' yet - with readings in tolerance on all ranges (when compared to a calibrated 8 III).

I noticed immediately that there was no serial number on the scaleplate, nor was there a 'Power Factor' scale. (see attached pic). There is a serial number on an 'AVO' sticker on the side of the case: 55547 40/2/75 (the 555 is blacked-out or worn away). The only number on the scale (lower LHS) is a part number: 3824-149. The part number of the facia (stamped inside level with the terminals) is 50074-A.

The battery cover is a flat plate identical to an AVO 8 II or III, and the case is similar bakelite material but with two securing screws down the longer edges instead of the one-screw-per-side of the 8 II / III. The inside is clean and appears immaculate. The 1.5V cell opsition has a rectangular adaptor, and there is the merest sign of corrosion on one of the 4.5V nuts at the bottom of the battery compartment. The moulded logo on the facia just says 'Universal Avometer' as opposed to 'Model 40 Universal Avometer', and the main terminals are the 4mm socket red-and-black type. The Power Factor terminals are recessed.

Was this meter really made in 1975? When was the Model 40 discontinued? I suppose a clue would be the wording on the rear instruction panel: 'AVO Dover, England'. Member of the Thorn Group'. There is no instruction regarding Power Factor measurement, and I wonder: would a PF and Wattage unit be available with suitable instructions for the modern scale?

I have an original handbook (part number 10072/25 5,000 5.52 - May 1952?) for an earlier meter. Do the specifications still hold for my AVO 40?

All information gratefully appreciated.
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Old 16th Jul 2008, 8:21 pm   #312
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Default Re: AVO Multimeter survey

My AVO is a model D, serial #D12048-1143, bought in all places at a ham swap meet in California. Must be a military surplus meter as it has a Air Ministry label at the top of the dial.
John.
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Old 16th Jul 2008, 10:54 pm   #313
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Default Re: AVO Multimeter survey

John,

The Model D was essentially an Air Ministry variant of the Model 40.
It was ssentially the same, but with a K=1/K=2 switch instead of a DIV 2 button, some resistor value changes to suit the different ranges, and no high resistance range - the military equivalent of 'Occam's Razor' being "don't use more than one type of battery".

rwb,
The Model 40 continued in production until at least 1978.
The reference to Dover makes it post mid-1962.
Your picture shows blue composition resistors on the multiplier board, which further confirms its late date.
The Model 40 never had a power scale (unlike the Model 7), but there was a "Power Factor & Wattage Unit" accessory, (valid for both Model 7s and Model 40s with PF sockets at the top - the early ones didn't have them). The PF&WU was a black aluminium, AVOmeter-sized, box sporting a shiny aluminium face with a printed quadrant scale and a knob with large perspex pointer attached. This was used to apply a voltage-derived current (to the PF sockets) to back-off the reading from the normal AC current scales. You needed a Ph.D to drive it, though the Unit's lid contained a circular slide rule to reduce the pain !

The Unit also had a drawer to house the connection cables.
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Old 17th Jul 2008, 9:06 am   #314
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Default Re: AVO Multimeter survey

Quote:
Originally Posted by SPCh View Post
The Model 40 continued in production until at least 1978.
Blimey! There was obviously a market for this type of meter, even then! I am thinking that my particular model was produced with cost-cutting in mind, using 'parts-bin' components (no fancy battery cover with prod-holders; similar case to the models 8 and 9). Would this tie in with Thorn's attitude to AVO production methods described elsewhere on this forum? It's no worse an instrument for this, I might add...

Would the date be part of the (stuck-on) serial number? Would my instrument have been made in February 1975 - and are the spec. and component values the same as earlier, ie: 167 OPV or 333 OPV with the divide-by-2 depressed?

Quote:
Originally Posted by SPCh View Post
The reference to Dover makes it post mid-1962.
Your picture shows blue composition resistors on the multiplier board, which further confirms its late date.
The Model 40 never had a power scale (unlike the Model 7), but there was a "Power Factor & Wattage Unit" accessory, (valid for both Model 7s and Model 40s with PF sockets at the top - the early ones didn't have them). The PF&WU was a black aluminium, AVOmeter-sized, box sporting a shiny aluminium face with a printed quadrant scale and a knob with large perspex pointer attached. This was used to apply a voltage-derived current (to the PF sockets) to back-off the reading from the normal AC current scales. You needed a Ph.D to drive it, though the Unit's lid contained a circular slide rule to reduce the pain !

The Unit also had a drawer to house the connection cables.
Thanks for the info; much appreciated. I won't actively be seeking out a PF unit, but I remember learning about the PF function - vaguely! - when I was an apprentice electrician in the 1970's.
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Old 17th Jul 2008, 10:18 am   #315
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Default Re: AVO Multimeter survey

Russell,

As you surmise, the production date of your Model 40 will be 1975.

This meter is as close to the "Universal Avometer" of the early 1930s as you would then have found. It is derived directly from the 20-range Universal Avometer introduced in 1932. By adding a 'divide-by-two' button this became the 34-range model and that very quickly acquired a 480V (AC) range to become the 36-range Universal Avometer in June 1934.

Two years later, the Model 7 was introduced and that had a completely redesigned interior with improved switches and, most significantly, an automatic cut-out which operated on pointer acceleration as well as end-stop force.

The 36-range type was advertised up to 1939 when the Model 40 replaced it. The essential change was to use Model 7 construction, including the cut-out. In the late 1940s, all Avometer movements were redesigned to use block Alnico magnets rather than the horseshoe cobalt-steel types previously used.

As mentioned before, there was a major value engineering review under Thorn management, the most significant result being the Model 8 Mark V. At the same time the Model 7 and 40 designs were reviewed and the result was the changes you see. Most of these reflect developments in the electronics industry generally.

It should be remembered that the Avometer was introduced at a time when there was no electronics industry which would have been recognised by that name; there was little more than LF radio.

By the 1970s, the electronic industry was considerably more mature and served a diverse range of applications which demanded more accurate and reliable components in huge quantities.

In the 1970s redesign for Avometers, many more component resistors were used, although the values were specific to Avometers. (This was a process which had begun in the 1940s when high grade, high stability resistors became available). More modern capacitors too were chosen and the cut-out components were changed from sheet and tubular brass to aluminium alloy die-castings. The movement was essentially the same, except that the alnico magnets had been replaced by alcomax blocks.

The result was a lighter instrument, considerably cheaper to make and at least equally accurate when new. Over time it would become apparent that the resistors could drift or fail in a way that the resistance wire windings did not, but by this time the wire could have been expensive to buy in as it was no longer widely used.

Many of the last of the Model 40s would have been bought as an 'electricians' meter, by colleges, public utilities and government departments, in some cases to match the recommendations of service manuals. What had been introduced as a general purpose multimeter, "Universal" in the sense of its range of applications as well as the intended sense of suitability for AC or DC measurements, was now regarded as a meter for "power" applications.

It was also during the 1970s that Avo began to offer digital multimeters and these were advertised alongside the traditional moving coil types.

The attached price list shows the multimeter range on offer in April 1980. You would have had to want a Model 40 quite specifically by then as it was roughly 25% more expensive than the Model 8, or the digital DA116 then being supplied to the Royal Navy and used in its submarines and possibly much more widely. Note too the "low-cost" instruments lower down the list, the cheapest being sold under the Taylor label.
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Old 17th Jul 2008, 12:32 pm   #316
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Default Re: AVO Multimeter survey

Quote:
Originally Posted by pmmunro View Post
As you surmise, the production date of your Model 40 will be 1975.
This meter is as close to the "Universal Avometer" of the early 1930s as you would then have found...
PMM,

Many thanks indeed for a thoroughly comprehensive and knowlegeable post. I've seen snippets of what you've written in various posts, and I apologise for getting you to go over old ground once more.

You ought to write a book (or maybe you have and I've missed it)!
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Old 17th Jul 2008, 6:24 pm   #317
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Default Re: AVO Multimeter survey

Another one i have just picked up is a 7x panclimatic serial number 90265-A-363. I think is is an ex MOD navy one. it has come in its original avo wooden box with leads and probes.
Also has a 3,600v multiplier 240 and 60A multiplier. along with a 480 and 120A shunt.
looks like new

but no batteries

can anyone tell me which batteries they are please.

cheers Mark
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Old 17th Jul 2008, 7:46 pm   #318
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Default Re: AVO Multimeter survey

Mark, The batteries will be a U2 for the low ranges, and two "1289" "flat" batteries for the high.

Thanks for the serial number.
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Old 18th Jul 2008, 10:50 am   #319
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Default Re: AVO Multimeter survey

Here are couple of pictiure of the Panclimatic. The serial number on the movement is as quoted, however there is a second number on the case above the movement. This is 6625-99-943-1531, as can be seen the U2 or D cell battery compartment has differing connections to those in a threat elsewhere. The flat cells for the High ranges look as SPCh has described.
There is also a P and Q button/switch which I have not seen on the Avo 8 mk 6 I have.

cheers Mark
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Old 18th Jul 2008, 2:31 pm   #320
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Default Re: AVO Multimeter survey

This is a smart, modern Model 7 supplied to the military.

The terminals for the 1.5 volt cell are there because the original battery box was designed for a rectangular cell with screw terminal and flying lead (see thread elsewhere) and this box was still fitted long after such cells had become extinct (possibly to use up old stock, possibly to avoid the cost of a redesign). My learned friend PMM has reminded me of an adaptor which AVO supplied (I assumed it was only for 'recovering' old models, but it seems they were also supplied with new ones) which made the rectangular/cylindrical substitution easy.

You'll have to solder flying leads to the + and - ends of the U2/D cell and fit them to the terminals. The positive should go to the left hand terminal (on the centre-line of the cell compartment) and the negative to the right hand terminal. (In every example I have they are marked + and -, but you need good eyes, good light and perhaps a magnifing glass to see them)

In answer to your auxiliary questions (and I'm not sure this is really the right thread to do so - Moderators feel free to move as appropriate) the P knob is used (together with the R knob) for zeroing the meter prior to making resistance measurements.

Set the range switches to DC and 100k ohm, short the leads, and adjust the P knob for approximately full scale deflection. Switch to the 10k ohms range, and adjust the R knob for JUST OVER fsd. Go back to the 100k range and adjust P for exactly fsd. Repeat as necessary until you can switch between 10k and 100k ranges with the pointer staying solidly on full scale. Now you're ready to start reading ohms.

The Q knob is what makes the Model 7, for me, one of the cleverest in the whole AVO family. It adjusts the effective sensitivity of the movement, and allows a whole host of other measurements - high resistance (using an external voltage sources), capacitance and audio power.
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