Avometer 8 Multimeter, Mk. III & Mk. V types: History, details, restoration, demonstration, theory

In this video, I talk about the history of the famous & iconic Avometer, a product of England, which is considered to be the "original" multimeter. I then show my two Avometers, both of them Model 8 types, with the older one being a Mk. III from the 1960s and the other being a Mk. V from the 1970s. I then talk about the small amount of restoration work I have done with them, and finally give a presentation about the theory of circuit operation.

Index of video chapters:
00:00 History
07:46 Mk. III views
31:49 Mk. III restoration
34:34 Mk. III "cut-out"
36:39 Mk. III schematic diagram overview. oddities & issues
48:40 Some issues with variations of models & marks
49:19 Mk. III demonstration
59:04 Batteries for both versions
59:28 Mk. III conclusion
1:01:40 Mk. V case opening
1:02:51 Mk. V views
1:06:57 Mk. V demonstration
1:17:44 Mk. V batteries , miscellaneous & case closing
1:20:06 Mk. V beauty shot
1:20:25 Mk. III theory of operation
1:31:03 Mk. V theory of operation
1:39:34 Combined Mk. III & Mk. V beauty shot

[cbiz]

Keep in mind that this AVOMeter is designed for horizontal position work,

[mohinderkaur]

Very nice explanation! The use of transformer is a nice way to do it

[MarkGeraghty]

There was also an AVO 8 mark VII. They come up for sale on eBay quite often. I have an AVO 8 mark VI, an AVO 9 and an AVO 8 mk III. The Avo 8 mk VI is my favourite.

[grahambambrook]

Nice to see someone from your side of the 'pond' appreciating products from our side. I know it's hard to believe now but we used to be an innovative, and industrious nation prior to the 'Banksters' getting control of everything. 😆
I have the Model 8 MkV which is a great piece of kit for certain functions. The only issue I have is [lack of] availability of the 15V battery at sensible prices but the one you show looks good if I can find one. To be honest I'm not that bothered as I don't tend to use it for resistance measurements.

[simontopley]

I've got a veritable collection going on, been buying up the really old type, they make interesting lamps.
I've got a mk5 with a yellow dial legend, it seems too constant to be fading, i wondered if it was an anniversary special.
The later ones were all made in Dover, just at the end of the A20, in the shadow of the Western Heights forts.

[PurityVendetta]

The correct pronunciation, well here in the uk, is the second one. I have aquired a few, I've lost count, of these meters in cluding an Admiralty version complete with a full set of hight amperage shunts all boxed together.
I still use a later AVO Mk 8 on my bench as I find it is more effective in measuring whether diodes have failed in circuit. I have no idea why this is and would love to hear if anyone hasba theory as tobwhy this might be. I have many bench and portable multimeters frome a Fluke 8810A 5 1/2 digit down but still find the AVO very useful in certain circumstances.

[zxztv]

I was surprised that anyone would be interested in an ancient old Avo . AYY-VOW :-)
I had a avo-8 given to me, the previous owner dropped it :-(, cracked case and smashed glass.
The meter movement worked but the linearity of the meter was way off, i checked all of the resistors and anything i thought could be the problem.
All of the components were fine.
I saw the thick metal plate on the movement with a screw through it.
I came to the conclusion that i could not make it worse so i loosened the screw and slid the plate and the movement became better.
When i was finished i managed to get the movement linear and lined up with every measurement.
I'm sure you know all about that, but i was finding out for the first time.
I didn't need to touch anything else, the voltages were spot on.
I also have one of those newer avos the one with the blue ribbon tracks, one resistor was open circuit, easy fix.
Sorry for the long comment.

[ianberry]

Did you know the later models of the Avo 8 range had a completely different of movement. Gone were the pivot and jewels movement, and in comes a taught band suspension type. This move was a down grade as whole movement would collapse, and the ring magnet would go off centre