Presentation Vintage Industrial multimeter BBC Goerz Metrawatt MA4 S

[Kiriakos GR]

At 13 March 2010 I scored on eBay in Germany this BBC Goerz Metrawatt MA4 S.

I will admit that it was something like Love at first sight the selection of this multimeter, back them I have a hobby to repair digital cameras, and I felt the need for one analog meter.

The usual problem with those Olympus C2100 UZ is that after getting old of 8-10 years, failing parts cause leakage current that is enough to empty the NiMH batteries in it even when is powered off. 

For such tests of leakage current, normal operation, flash use, zoom use,  all this activity happens very fast, and only one analog meter is capable to give a better picture of what is happening.

By getting this multimeter in March of 2010, I did discover several innovations:
This meter is a Rarität industrial grade multimeter (electrical engineering) of 80s.
With amazing specifications as for example bandwidth up to 10KHz, plus amazing accuracy in full scale, and also active protection with internal electrical relay which cut off the test leads.
Externally the meter is tremendously durable, and event factory tested up to 2500V.

For now I will post some pictures of how the meter looks externally.
And soon I will add some pictures of the internals ( I have never seen a true silver plated PCB before). 


BBC Goerz Metrawatt MA 4S  & brother model METRAVO 4S   

Technical specifications:

• Voltage ranges:
DC: 75mV, 750mV
AC / DC: 2.5 , 7.5 , 25 , 75, 250, 750V

• Bandwidth:
AC  2.5V ... 250V 10k Hz
AC 750V 3k HZ
Lowest frequency 25Hz
Best accuracy 45~500Hz (Mains and up to Aviation PSU)

• Current ranges:
DC: 75uA & 750uA
AC / DC: 2.5 , 7.5 , 25 , 75, 250, 750 mA
AC / DC: 2.5 & 7.5 Ampere
AC / DC: 25 Ampere Add-on input (overload 150A for 5 seconds).

• Ohm ranges:
x1 Ohm & x100 Ohm

Measuring accuracy: class 1.5 for AC / DC
Class 1.5 for resistance
Read off the mirror scale to paralax-free
 
• Power supply:
9V block / protection relay
1.5V baby cell / Ohms measurement

• This multimeter has a built-in several overload protections.
Due high power diodes
Due fuses
Due protection relay

[Kiriakos GR]

 

[giorgos]

You got in in a very good price, also it seems to be in a great condition (i suppose that you bought it as used).
I search e bay very often to find good offers like this but its seem to be rare. As usual they offer used instruments in unaccepable high price although the condition of them is not good. So in this case you had made a good purchase.

[Kiriakos GR]

It is true that this meter is in great condition, which is a surprise even for me.
After testing it by comparison to the most fresh and crop of the cream digital multi-meters, it great accuracy made me to appreciate it even further. 
The clear to read scale made me to like it even more. 

In summary this specific model is by far superior than any Asian assembled analog meter even in 2013.
But I can not say the same for the latest digital Gossen Metrawatt, they belong to another era, and there is not much information about how well they perform in comparison with other modern meters of 2011 - 2013.

[Kiriakos GR]

Pictures from the internals .... 

This is a multimeter made to handle 25A continues, and so what you will see is different than anything before.
There is two PCB  boards inside, I describe them as PCB layers.
The top is about mostly low current circuitry, the bottom one is for high current and for the relay.

The range switch extends in both PCB, and controls contact points in both.

I am not brave enough to take it completely apart, I have never see one so difficult to take apart instrument.

But I did open it, because the zero ohms knob this got out of position, probably when it got shipped.
Thanks God nothing was damaged, only the plastic super long knob was not properly attached on the potentiometer.

[Kiriakos GR]

Last set of pictures.

 

[Kiriakos GR]

I was not aware that PORSCHE designed multimeters but it did.   

[Kiriakos GR]

Few weeks ago I had the idea to look for the English version of User manual of METRAVO 4S (this were sold in other markers than Germany).

In my research due Google, I discovered one blurred picture of  some one whom installed over his METRAVO 4S one power switch so to turn off the use of  the 9V battery.
I have also noted in my meter that for some mysterious reason this 9V battery it does draining all by it shelf and I could not explain it.

After some experiments I am now totally aware that MA4S and also METRAVO 4S, they always use their 9V battery voltage so to keep their internal relay switch in armed condition.
 
In simple English, internal relay switch this is a circuit fuse that requires a minimum portion of current flow or else it gets disarmed.
Disarmed = Volts and mA & Ampere ranges they do not measure anything.   

The addition of 9V power switch this is a tremendously smart idea,  when the meter gets in storage, you simply turn this off, and when you are about using the meter, all that you need to do this is arming the relay by using the Battery Test Mode.

Now in Battery Test Mode, I do find the indicator as very confusing,  the needle never goes all the way at the right (positive side),  neither you can read it and estimate some sort of percentage of remaining charge.

It would make more sense if this battery level indicator (horizontal line) was painted with Green – Yellow and Red color at it very left side.
Either way, yes I know this is technology of 80s and back then color printing was not popular.

Even so, I am very happy that I did discover this modification which helps me to save money on 9V battery costs (Alkaline ones).

[Kiriakos GR]

My BBC Metrawatt MA 4S, this started to have severe issues today.
I could not properly activate the protection relay so the multimeter this to start operating.

After an hour of pulling my hairs, I did discover the damage.

The original BBC Goerz Metrawatt 9V battery Clip this is now damaged.
Some one would expect, wires damage or soldering damage, but here we have metal surface damage because of the nickel plating. 

I did soldered a fresh Taiwanese 9V battery Clip, and my German super machine, this came back to life. 

Note: The corrosion was not formed due battery leakage.
This rare 9V battery Clip, stayed alive since 1986 up to 2025 = 39 years.