OT: Master Instruments Multimeter specification and schemati

[Ross Herbert]

Many here will know the name Master Instruments Pty. Ltd. Back in the era of
analogue measuring instruments they made very good meter movements and even
produced a general purpose field multimeter for use by the PMG Dept and the
defence forces. As supplied to the PMG it was designated APO Multimeter No. 3
and when supplied to the military it was designated Multimeter No. 4. I recall
that in the 1950's to mid 60's there were earlier iterations dubbed APO No.1 and
No.2.

I have an APO No.3 which was originally supplied to an engineer mate of mine
back in 1971 at a total cost of $68.50 without the carrying case. A leather
carrying case was added later.

Since I wanted to have some manufacturers literature on this meter I prevailed
upon Master Instruments to supply me with whatever documentation they may have
retained, but I was not expecting anything. I was rather pleasantly surprised
when they were able to supply a copy of the specification and a schematic.
Master Instruments no longer manufacture analog meters (or any other kind), and
95% of their business these days consists of supplying batteries.

Unfortunately, the quality of the documentation was not good enough for printing
with any degree of clarity so I have retyped the original specification in Word
format and added a hand drawn schematic of the meter.

If anyone would like a copy of this documentation feel free to email me for a
copy.

 

[Trevor Wilson]

On 8/30/2012 9:24 PM, Ross Herbert wrote:

Many here will know the name Master Instruments Pty. Ltd. Back in the era of
analogue measuring instruments they made very good meter movements and even
produced a general purpose field multimeter for use by the PMG Dept and the
defence forces. As supplied to the PMG it was designated APO Multimeter No. 3
and when supplied to the military it was designated Multimeter No. 4. I recall
that in the 1950's to mid 60's there were earlier iterations dubbed APO No.1 and
No.2.

I have an APO No.3 which was originally supplied to an engineer mate of mine
back in 1971 at a total cost of $68.50 without the carrying case. A leather
carrying case was added later.

Since I wanted to have some manufacturers literature on this meter I prevailed
upon Master Instruments to supply me with whatever documentation they may have
retained, but I was not expecting anything. I was rather pleasantly surprised
when they were able to supply a copy of the specification and a schematic.
Master Instruments no longer manufacture analog meters (or any other kind), and
95% of their business these days consists of supplying batteries.

Unfortunately, the quality of the documentation was not good enough for printing
with any degree of clarity so I have retyped the original specification in Word
format and added a hand drawn schematic of the meter.

If anyone would like a copy of this documentation feel free to email me for a
copy.

**Great service. I found the same thing with Iwatsu. I required a
schematic to track a fault in a 100MHz Iwatsu CRO a few years back. An
email to Japan elicited an instant response with a full manual in .pdf
form.

--
Trevor Wilson www.rageaudio.com.au

 

On Thursday, August 30, 2012 at 9:24:19 PM UTC+10, Ross Herbert wrote:

Many here will know the name Master Instruments Pty. Ltd. Back in the era of
analogue measuring instruments they made very good meter movements and even
produced a general purpose field multimeter for use by the PMG Dept and the
defence forces. As supplied to the PMG it was designated APO Multimeter No. 3
and when supplied to the military it was designated Multimeter No. 4. I recall
that in the 1950's to mid 60's there were earlier iterations dubbed APO No.1 and
No.2.

I have an APO No.3 which was originally supplied to an engineer mate of mine
back in 1971 at a total cost of $68.50 without the carrying case. A leather
carrying case was added later.

Since I wanted to have some manufacturers literature on this meter I prevailed
upon Master Instruments to supply me with whatever documentation they may have
retained, but I was not expecting anything. I was rather pleasantly surprised
when they were able to supply a copy of the specification and a schematic..
Master Instruments no longer manufacture analog meters (or any other kind), and
95% of their business these days consists of supplying batteries.

Unfortunately, the quality of the documentation was not good enough for printing
with any degree of clarity so I have retyped the original specification in Word
format and added a hand drawn schematic of the meter.

If anyone would like a copy of this documentation feel free to email me for a
copy.

Hello Ross. I have a No. 2 bought from a surplus shop in Albury Wadonga in the early 90's. I've given it a fair bit of use but have never had the benefit of resistance measurement as I've never known what batteries to use. Consequently I've mostly had a digital multi meter as well. I'm studying electronics - an elective as part of a teaching degree this semester and I want to improve its utility on my test bench by adding some batteries to it. Can you advise on what may be still available. I see you can still get the 15v dry cells for the English AVO's but their dimensions don't fit those of my No. 2's battery compartment, which has two different types of battery (possibly 3 cells). Also, if the schematic for the No. 3 relates in any way to the No. 2 - I'd love a copy of that. If you can still find it in your computer after all this time?

Thank you
Kind regards
Gilbert Louttit

 

[Phil Allison]

Ross Herbert wrote:

-----------------------

** Hi Ross.

Many here will know the name Master Instruments Pty. Ltd. Back in the era of
analogue measuring instruments

** Never new those days were all over ?

Since I wanted to have some manufacturers literature on this meter I prevailed
upon Master Instruments to supply me with whatever documentation they may have
retained, but I was not expecting anything. I was rather pleasantly surprised
when they were able to supply a copy of the specification and a schematic..
Master Instruments no longer manufacture analog meters (or any other kind), and
95% of their business these days consists of supplying batteries.

** You have reminded me of the day I visited Master Instruments at their factory in Marrickville, near Sydnenham Station. I was after a couple of Ni-Cd 7.2 volt packs made with Sanyo cells that were assembled on the premises.

Walking into the reception area was like going through a time warp, everything looked like it had not changed since the 1950s - the polished timber floor bounced gently as you walked over it. Staff were very friendly with a large percentage of European women doing assembly plus a few experts overseeing, mainly Aussies.

I could see they were still doing meter repairs on types they had once manufactured.

I spoke with a grey haired gentlemen who, after an internal phone call, explained that one of the women would have to finish off some incomplete Ni-Cd packs for me - if I didn't mind waiting.

It was 1991 or 1992 plus also Melbourne Cup Day and my arrival was a few minutes before the "great race" was due to start. So everything suddenly stopped.

A TV set on a tall stand and refreshments were brought into the lunch area and I was invited to take a seat. I was also offered a beer by another male staffer and accepted.

After the race finished, my order was processed along with a hand written invoice, which I paid in cash.

-----------------------------------------------------------

From the MI web site:

Established during WW2 to provide electrical meters to the Australian armed forces, the business is now in its third generation of Dunn family ownership and control.

https://www.master-instruments.com.au/

https://www.master-instruments.com.au/pages/company-history-overview.html

There were once many electrical /electronics manufacturing business like MI in Australia, I think of companies like Melbourne's BWD who made oscilloscopes and other test gear and Sydney's Patton Electrical who also made panel meters and the like plus AWA making radios and TV sets and AWV making all manner of electron tubes.

That MI have managed to diversify and expand when others collapsed in face of Asian imports is a great credit to the management. Moving into the battery business in the early 80s was well timed and evidently crucial to their current success.

Someone ought to make a TV doco about them.


..... Phil

 

[Phil Allison]

Ross Herbert wrote:

---------------------

I have an APO No.3 which was originally supplied to an engineer mate of mine
back in 1971 at a total cost of $68.50 without the carrying case. A leather
carrying case was added later.

** I note you are responsible for this page too:

https://www.radiomuseum.org/r/master_aus_apo_multimeter_no_3.html#b

From the pics, it looks exceptionally well made.

From the specs or your own testing, can your say what the frequency response of the 10VAC range is like ?

Is the 400uA movement "Taut Band" ??

Protected from overload by reverse parallel diodes ?


..... Phil