AVO Multimeter survey

[The Philpott]

The case looks like it's from the mid 'fifties.

Dave

[Electronpusher0]

Originally Posted by Sinewave

It's possible. Look on the back of the meter, there should be a 10S number on the rear plate.

The back of the meter has a number 10S/10610. The case is 10S/17021 so not the same.
I did think the case was in too good a condition for the age of the meter.
Oh well I need a decent case for my AVO 8 MkIII............

Peter

[Sinewave]

The numbers after the 10S may not be the same for the case and the meter. So there's still a chance they were made for each other.

[AndyGilham]

The 10S signifies the Air Ministry stores ref (stock number). The remaining numbers are sequential.
The type D 10S/10610 appears in early military documents, and also includes a leather case, but under 10S/10614. This implies your case marking is for a later model.

Andy

[pmmunro]

Andy,

I would be most interested in any military documents relating to 10S/10610, which might give an indication of the intended use of the Type 'D' multimeters. There was also an earlier specification, 10A/10610 which related to the first Type 'D' meters, the AVO version of which was based on the 36-range Universal Avometer.

I have a number of Air Ministry manual sections which describe the Type 'D' multimeters but none of these state their intended area of application. The ranges of these meters seem ideally chosen for 12 and 24V electrical systems on moter vehicles, which I understand were very similar to the simpler aircraft systems in the late 1930s and 1940s but despite a wide search, I have no documentary proof of this.

PMM

[AndyGilham]

Peter,
I'm afraid the information i have only is for the instrument specification and store number for the type D. I myself have been trying to find further millitary 'AP' specifications that cover these products, but with no luck!

Andy

[Barnmead]

Nice list of AM stores references here:
http://www.warrelics.eu/forum/battle...xxx-etc-82212/

[Sinewave]

Originally Posted by Barnmead

Nice list of AM stores references here:
http://www.warrelics.eu/forum/battle...xxx-etc-82212/

Excellent info in there.

Interestingly it appears our 10s Model D's are radio equipment meters.

[The Philpott]

In the context of use on a 12 volt vehicle, when set to the 30vDC range the needle points approximately to 'A' when detecting a normal alternator output voltage.

A coincidental and accidental use of the 'A@M' legend which appears on most Model D AVO's!

Dave

[pmmunro]

Dave,

An interesting oservation, to those of us of a similar mindset, probably labelled "sad" by the unenlightened.

I just had a quick look at AP1186E to check for myself; it's not too clear in the photograph on Page 2 but it's also interesting that the meter in that picture is built on a Model 40 front panel. It would also appear to have flat-topped, low profile selctor switch knobs and an aluminium back case.

The image which I've attached is reduced to make the file size uploadable on the forum but on the original I think I can just make out the serial number as D426-139 1939, or possibly D126-139 1939. That would suggest that the use of Model 40 front panels was not just a war-time expediant, or possibly this was a prototype, but that doen't quite square with the serial number.

PMM

[Sinewave]

Originally Posted by pmmunro

An interesting observation, to those of us of a similar mindset, probably labelled "sad" by the unenlightened.

The unenlightened are a real problem.

The Avo King they call me at work, whilst they point and laugh.

"How many have you got in your collection now?", they ask, whilst fighting back tears of laughter.

[The Philpott]

My meters were once deemed 'of no use' by someone who collected (collects) large amounts of small PVC caricatured dolls of characters from movies and TV- i maintained a dignified silence.

The leads in Peter's image with the threaded accessories look very similar to those supplied with the Type E, but with split pins substituted for 'C' forks (both types of termination made under the CLIX name)

The lack of tinning on the wartime multicored leads makes me wonder if by some means this accelerated the deterioration of the rubber, notwithstanding any number of other variables the leads would have been exposed to.

Dave

[Barnmead]

I see that the picture posted by PMM (#2150) is labelled Testmeter Type D.1. There is an identical picture in AP 1095H labelled Testmeter Type D

So two distinct versions then?

[AndyGilham]

Originally Posted by The Philpott

My meters were once deemed 'of no use' by someone who collected (collects) large amounts of small PVC caricatured dolls of characters from movies and TV- i maintained a dignified silence.

I work for Megger and get the negative comments at work from colleague about my historical interest. Daily I hear 'why are you still bothering with that old crap' and I just reply, it's because of that 'old crap' you have a job here!

It's become a hobby for me..... And speaking of said hobby, I picked a Model 40 Mk 2 at a local boot fair for £10. It came with leads, clips and probes and supplied in a leather case. Externally it contains no serial number, so I need to open her up and have a gander! (At work, to annoy my colleagues)

Andy

[pmmunro]

Type D was an Air Ministry specification and was met by meters to the same specification by Salford Electrical Instruments Ltd and by GEC, whose Type D was labeled “Selectest IV”.

While they now seem to be less common, the survival rate of the SEI and GEC types would suggest that, like the Avometer, they were made in large numbers.

PMM

[AndyGilham]

Another Model 7 arrived today, with serial number 7129-3427, making it a December 1939 model, so nice and early. This instrument included the ‘model 7’ moulded panel and metal casing.
Internally, there seems to be some ‘re-work’ completed at some point. Although the same serial number on the rear movement plate.

Andy

[duncanlowe]

Interesting that SEI are mentioned. I worked with them for many years but they no longer made instruments. I used to visit Times Mill, but it is now a Morrisons.

[The Philpott]

That's very similar to My Model 7, Andy. (June 1939)
I theorised that it might have originated from a shadow factory, as the build quality was shoddy in places and i wrote two sides of A4 detailing the work required to make it happy. I never did (bother to) get the capacitance range working properly. I can share these notes if turns out to be of any use.

The movement, i recall, is very healthy.

Dave

[AndyGilham]

Dave,
Yes I hear murmurings of this shadow factory, but have found no evidence of it. I'd be I tersted to see your notes, see how the quality of my instrument compares. It would be nice to have a library of internal and external assembly photos for all these model variants. I am up to 12 variants for model 7 mk1 and mk2. Its a minefield!!

Andy

In my own research:

13 7 MK1
5 7 MK2