Presentation Vintage Industrial multimeter BBC Goerz Metrawatt MA4 S

[Kiriakos GR]

What do you consider as reasonable price, for these multimeter, at the market of used ones?

For a multimeter in pristine condition and undamaged, I would not pay more than 50 EUR.
The electronic circuit includes large amount of custom made components, these are close to impossible to be found as spare parts.
Metrawatt of our times, this is disconnected from that era of products.

Any survived up to date, MA 4S / Metravo 4S, they manage to live that long, thanks to their:
• Extended Number of Fuses and Relay electrical protection circuits.
• Printed circuit this is covered, due our well known Green protective varnish, this kept the PCB safe.
• Along of their soft carrying bag, which this kept intact multimeter mechanical parts, along it casing and aesthetics. 


Here I made a topic with relative historical facts.
https://www.ittsb.eu/forum/index.php?topic=2062.0

[Kiriakos GR]

Since August 02 2013, never touched my multimeter calibration.
Back then, I was not having the necessary precision references and sources, as I do now.

DCV & DCmA Calibrator | Highest precision resistors decade box | ACV stabilized source along Variac Transformer.

In conclusion:
I feel today extremely happy, because even the oldest multimeter in my bench, this is Calibrated and adjusted, with quality of sources that neither Metrawatt lab had at 80s.   

The only thing missing, this is a Calibration sticker. 

[Andrew-88]

!!!   

[Kiriakos GR]

It looks like that I totally skipped to pay much attention at Resistors Ohms ranges.

The question is of what is lower measured resistance that you may trust, due MA4S and lowest  0~1K Ohm range.
At Ω / 1 position, DC voltage supply 1.5V and Current source this has I Max of 50mA.

AI assistance succeed to give me high definition hints, of how this range behaves electrically and according to Law of Ohms.
1.5V + I max of 50mA ( leads zero), this brings the meter at 30Ω Internal Meter Resistance.   

At that point any measured resistance this is added on top of this 30Ω ( Leads Zero) resistive load.
From the other hand, actual meter scale, this is able to deliver highest detail when you are measuring from 0.5Ω up to 5.0 Ω.

MA4S current source this has a range of supplying currents, and at Full scale 1KΩ, current source output gets as low as 1.45mA 

Why I got motivated so to lookup at these details?
Because at digital multimeter the vast majority comes with 600Ω range, and this appears poor choice at measuring very low resistance at 0.5Ω and lower.

MA4S current source this has equal specifications with FLUKE 289.    
FLUKE 289 this has 50Ω lowest range, but due it 50mA current source, this were advertised for measuring motor winding resistance, and electrical relay resistance.
In our times, an 50mA current source this is forbidden to be used at miniature sized passive components over a PCB.

At 2012 and later, it came one innovation at our planet, this is named as U1272A with 30Ω range, this using modern circuits and Low-Power current source, that is the ideal combination for measurements over miniature sized passive components over a PCB. 

In summary.
Even MA4S this is designed to fit in world, for measuring motor winding resistance, and electrical relay resistance. 
And this is not a step back at it internal product design, MA4S this came first in our planet, than these miniature passive components. 
 

[overvolt]

It looks like that I totally skipped to pay much attention at Resistors Ohms ranges.

Excellent summary of facts.

MA4S undocumented strong points:
Measuring motor winding resistance, and electrical relay coil resistance, along of contacts resistance testing !!

[Kiriakos GR]

Indeed, from a plain ON/OFF switch testing, down to electrical relay contacts testing, MA4S this is at my bench, the proper tool for the job.
Under repeated tests, lets say ten times, if you get identical results at 0 Ohms, then this part it is working properly. 

The strong point of analog meters, this is instant review of unstable or stable conditions.
Digital bar-graph this trying to imitate, this specific functionality and this advantage, of analog meters.