AVO Multimeter survey

[pmmunro]

Palmerino,

That's an impressive collection even by UK standards. You must have gone to a lot of trouble to find them all in or from Italy.

Many would seem to be ex-military equipment.

PMM

[Herald1360]

I've acquired an 8 mk 3 in battledress I think. Describes itself as Test Set No 1 Multirange High Sensitivity.

There's a handwritten 7408 on the LHS of the dial.

Is that the serial number or will I need to get inside somehow?

[Palmerino]

Trevor

I thank you for your post. An arduos restoration work was surely but I am contented of the consequence. Avominor type E was an imaginative project for the era. It was small but many ranges, it was as well estreme.

Ciao, Palmerino.

[Palmerino]

PMM

Especially for my pocket is impressive. Ten research years are wanted there, particulary on Ebay, some postal bewilderment, the several of the Avos scourged
by the time or the misapplication. In the best hypothesis they was need of cleaning! Only two times (with a Avo8 mk1 and a Avo8 mk5) I found the untouched seals and calibrated. Earlier I do had leisure time, later whenI become engaged much less and I am fear that I will have yet less (in October) after the wedding! I went my first time in London in last January and lugged my (snorted) fiancee at the War Museum. I wanted to absolutely see a neighbor Spitfire. When we were the boys, my friends and I were thrilled in movies and comics of war. I found the nose of a Lancaster bomber very interesting with her radio booth alright visible. The Avominor type E what had DC only, was transported on the airplane? Do you have some news on the use of the 20A range?

Ciao. Palmerino.

[pmmunro]

Palmerino,

Thanks again for sharing your collection with us.

You raise a number of questions which are beyond the scope of the forum to advise on but it sounds like your fiancée is a very understanding person.

As well as the Universal Minor Type E, there are a number of military Avometers I would like to know more about, especially exactly where they were used. The 20A range on the Type E is the highest current range that I can recall on any Avometer, without using accessories, other the the Model 12, designed for auto-electrical work, which has a 36A range.

The other Avometer made specially for the Air Ministry is of course the Type D. I would guess that the Type D was intended for use on the main electrical systems of aircraft, while the Model 7 would have been used for aircraft electronics.

I will post aseparate thread asking if anyone knows of friends or relatives who served in the armed forces and who might remember details of using Avometers.

PMM

[Barnmead]

Good evening
I have just acquired a model D serial number 21272-845 in almost pristine condition complete with cloth covered leads, clips,probes and AM leather case. But the pointer would not swing freely and the balance weight was absent. After rectifying this I found that it read low on volts and amps. I discovered that more than 3mA is needed to get full scale deflection. I wondered if the movement might have come from a model40 but the pencil markings correspond with the serial number on the scale plate. So just a showpiece at the moment!

[pmmunro]

Richard,

The basic movement characteristics of the Type 'D' movement are 2.5mA, 50mV fsd, and 20 ohms resistance with swamp.

3mA sensitivity is a bit low but have you tried adjusting the magnetic shunt on the magnet? It consists of a pair of steel strips clamped on the horseshoe magnet. Slackening the clamp screw allows it to be moved up the magnet to increase the sensitivity.

If the range of adjustment is insufficient, the best remedy is to have the magnet remagnetised, but finding someone with a suitable magnetiser is not easy. Some people have tried adding high field strength miniature magnets with some success but movement linearity could be poor.

PMM

[Barnmead]

PMM
Thank you, I couldn't see the steel strips you mention but there is a rotatable adjuster which can be seen below the rectifier. The only other steel shunts are the pieces that hold the pole pieces together. the pieces of magnet that I tried on the underside of the movement almost did the job but were too big to be accommodated in the meter casing.

[pmmunro]

Richard,

Sorry for misleading you; I was thinking of the earlier horseshoe magnet Avometers.

The attached photograph shows the magnetic shunt on a Type 'D'.

If you want to discuss the problem further, it would probably be best to start a new thread as we are risking going off topic for this one.

PMM.

[Barnmead]

PMM
Thank you, with two magnets it is back in business! I will start a new thread.

[IanG3XYV]

My Avo Model 8 Mark 2 is 9xxxx-C-759.

Ian

[G3VFB_Anton]

To add to the survey - have found in my 'turnings out' an ex BBC meter which I have cleaned up a bit, replace batteries and it all seems to work lovely. Can't recall where I got it from...

Universal Avometer Model 8 Mark III Model B. No. 73052-168

[AC/HL]

One post moved here: https://www.vintage-radio.net/forum/...d.php?t=127828

[AC/HL]

One post moved here: https://www.vintage-radio.net/forum/...d.php?t=128261

[Pmark34]

Hi all
Latest in the ever growing collection, another Avo model 12 (no. 6587 10 80. so October 1980), with accessories, fully working & in great condition. Also with the instruction booklet, Dated 1971 & its Warranty card.

[martiR2R]

Picked up another one today,Model 8 Mk2, S/N 152374-C-263.

Regards
Martin

[ahankinson]

Just picked up one! A "Test Set No. 1" with "HM Dockyard Portsmouth" and "Propulsion System Team No. 007" on it. Serial # 10.XXX.1170

[mole42uk]

I've just added an AVO EA113 - serial on the scale is 494-1069, stamped on the backplate is 388

It needs some work, the batteries had been left in and had dribbled :-(

[The Philpott]

Model 47A No.17543-1144 R (?)

This one is worth mentioning as it closely relates to a discussion Nicko and pmmunro had back in April 2011 (page 33).

The rear has a Model 40 instruction plate (not surprising) but it included reference to the internal 4.5volt batteries... so i opened it up to see that it does indeed have the huge Model 40 battery box- with provision for 1.5v and 9v feeds, giving 3 onboard resistance ranges rather than the 2 i was expecting. Four battery spikes are present in the AVO so it appears to match the battery box with it's 4 leaves.

Now on the front of the case above the 47A legend, a letter S is painted. I paid this no attention at first, but it matches Nicko's AVO so it appears to be 'correct' and contemporary. Provisional conclusion: Model 47AS had 3 onboard ranges and 47A has 2.

In my box of oddities from a different source is a small enclosed shunt marked AVO 47A 12+12A. It appears to be 33mV drop per amp- an odd value- and i can only think that 47A instruments may have been supplied with this shunt, to restore and possibly extend full functionality in the event of the 12A range expiring in service when many miles from a repair workshop. This rating would give 36A on the 12V range, which seems like a lot for it to handle. It's only the size (and colour) of a cigar and clips neatly across the AVO terminals.

Correction- shunt would give 36A on 1.2V range, (not 12V range)

[JohnMcGivern]

Hi all, hope everyone all ok. I have an Avo 8 model no. 10620.C. 464D. Any info would be nice. Not had time to check out yet.

Regards, John.