OT: Master Instruments Multimeter specification and schematic

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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.

Re: OT: Master Instruments Multimeter specification and schematic
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printing
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**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

Re: OT: Master Instruments Multimeter specification and schematic
On Thursday, August 30, 2012 at 9:24:19 PM UTC+10, Ross Herbert wrote:
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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 bene
fit of resistance measurement as I've never known what batteries to use. Co
nsequently I've mostly had a digital multi meter as well. I'm studying elec
tronics - 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. Ca
n you advise on what may be still available. I see you can still get the 15
v dry cells for the English AVO's but their dimensions don't fit those of m
y No. 2's battery compartment, which has two different types of battery (po
ssibly 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 comp
uter after all this time?

Thank you
Kind regards
Gilbert Louttit

Re: OT: Master Instruments Multimeter specification and schematic
Ross Herbert wrote:

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

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** 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  






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