10 milliohm shunt - Fluke 80J-10 100mV at 10A AC/DC

[Kiriakos GR]

Fluke 80J-10 this is a current shunt made back at 1977,  what is impressive this is tight tolerance which this was made.

I started discovering the world of current shunt this month, mostly because I am not any more limited regarding multimeter resolution in digits (8846A), and also because of I did find a branded special resistor so to play with. 
This is a Current Sense Vishay Dale 10 mOhms R01F resistor.    

Originally I thought to discover due experiments of how far I can go with a 10 milliohm 1W resistor, the wattage originally seems low but now I discovered another new world. 
Vishay Dale 10 mOhms R01F resistor this succeed to operate at 15V 7A that is 105W load by this getting just warm at 35C (24C room temperature).

Vishay Dale 10 mOhms R01F this has 1% tolerance but my sample this measures +0.3%, now when this resistor become warm (35C) actual tolerance value this changed to +0.8%,  and when this cooled down it did return to +0.3%.

Vishay Dale R01F this is not a metrology class resistor, even so it behavior it did helped me to understand the importance of tight in tolerance current sense resistors.

Fluke 80J-10 this is also 0.010 Ohm shunt with  +/_ 0.25%  tolerance and temperature coefficient of 0.005% per Celsius.
R01F this has 75ppm per Celsius, this is temperature coefficient of 0.075% per Celsius.

I found few pictures to share from it, but nothing for it internals.

My new mission this is to discover most accurate current sense resistors and their true wattage handling limits.
 

[Kiriakos GR]

It seems that I am getting more understanding by its next hour.   

This time I gained awareness of how far I can go at exploring tolerance and accuracy specifications.

Starting from my 8846A and by exploring it accuracy specifications at 100mV DC range this now it can deliver accuracy of 0,0072%  ± (% measurement + % of range 1 year).
Additionally 8846A on-board shunt (1~10A) this is also at 0.010 Ohm  and measuring accuracy this is 0,07%  (% measurement + % of range 1 year).

Therefore up to that point, I am now able to evaluate any shunt regarding mV output down to 0,01% accuracy.

HIOKI RM3542A this is my second workhorse which this aloud me to identify due it comparator function any tolerance deviation down to +/- 0,000 % 

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Now regarding resistor shunt wattage and shunt resistor properties.
I have to admit that resistors wattage calculation this is not my strong point, this is a topic for electronics engineers which they received proper training so to handle.

Even so, it seems that mV output of shunt resistor at 100mV output at 10A and when both values get multiplied, end result this is 1 Watt.
My WSL2512 this is 1 Watt. 

Respectable manufacturers of current shunt resistors they did calculated inrush current and such resistors while they have named specification of 1W, they are able to handle double or triple current for a limited time.

Now it also starts to makes sense of why Vishay Dale 10 mOhms R01F resistor this capable to survive thermal shock up to 170 Celsius with out destruction.

Practically all modern handheld and benchtop multimeter these protected by HRC fuses they will do a good job with out ending up with a burned current shunt.
In case of a wild event HRC fuses will blow fast enough and prior the shunt to get misused by over current.
Few months ago I was invited to repair one 8840A with burned current shunt and the repair was not possible due lack or spare part availability.
       
Spesific topic this is here to serve as information and also as warning, any violation of fuse specification (10A),  this will be destructive for the multimeter.
The smoking gun which did permanent damage at this Fluke 8840A ( burned current shunt ) this is by 99% a HRC fuse blown and sorted by copper wire.