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31
I am reading my articles which I wrote six years back and now that I am much more expert I do not feel the need to change a single word.  :)

Yesterday I did maintenance at my FLUKE 8012A,  push button switches was not operating freely, and measurement rate also seemed slow to stabilize.
I did use Testanol electrical connection and tuner spray, and everything now returned to normal.  8)

For once more time I did tested the Low-Ohm range, this has two available options:  2 Ohms range and  20 Ohms range.
This time I tested one 10 milliohm shunt resistor,  and the meter was spot on.
I did also check FLUKE 8012A Low-Ohm range specification, this has a accuracy tolerance of  +/- 1%.
 
Therefore  2 Ohms range with +/- 1%,  this is still usable even today for evaluation of current shunt at not critical applications.  ;)
32
Now within 2019 I will also deliver and a second recommendation.

This week I did receive and inspect shrouded female banana plug, this is for the application of wire extension or about making DIY test leads.
In the positive side of things, this banana barrel resistance it is comparable to gold plated Multi-contact female banana plug.
But do not be confused...  buying such female banana (China) this is now somewhat safe choice, but mechanical construction and product quality of male banana plugs this is still questionable.

Vast majority of Industry of China they expect customers requiring banana plugs for Audio Applications and Radio controlled toys.
Shiny-Gold bullet style banana plugs these are disposable RC toys connectors.

Another detail about these shrouded banana plugs, the hole at the top ( entry for the wire) this is very wide, the manufacturer recommends use of silicon wire with a large diameter.
Quality double insulation PVC wire for multimeter test leads this has diameter of 3.63 mm and this is not wide enough to fill the gap of 4.4 mm.
Because of this detail I am now adding a few turns of insulating tape so to increase wire insulation diameter and make it compatible with these banana plugs.    ;)   

 
33
It took me only five years so to discover that my first choice of economy banana plugs this is described as 25.412 nickel plated 4mm Banana.  :)
And this is not all,  I was lucky to find and product specifications diagram. 
 
34
Not many using Wago 222 or clones, but electricians will feel more tempted than others about to use such clip style connectors possibly as temporarily multimeter connection point with bare wires.

Practically anything can be clamped over a Wago style 222 clip, but BEWARE ...  high quality test leads with 2mm tips they are all nickel plated copper ... and Copper this is SOFT metal.
Wago style 222 clip this is designed to operate as anchor of copper wire by not taking in calculation quantity of force and clamp design regarding compression of test probes tips.
 

Therefore this thought while it seems as practical, this is dangerous for the health of the test leads tips.
Nickel plating among copper 2mm tips they will be heavily damaged and corrosion will start to appear over the tips, end result will be pair of test leads to be trashed prematurely.   

There is one exclusion in the above thought, this is if you own by choice test leads with hard (no copper) tips.
Such selection of test leads this is not random thought, some electricians they do prefer such multimeter test leads so to do piercing of wires and or to measure car batteries.

It would be more wise thought for you, about to follow DIY root and proceed and make a dedicated accessory (pair of cables) with insulated male bananas and Wago 222 as termination at the other end.  ;)
           
35
MFJ brand or MFJ Enterprises, Inc. , this is not a European problem because this is in the USA.  ;D

I was investigating to get ideas about DCV Multiple Outlet Panels and I came across to this product, and very soon I came also across of a customer testimony that this product arrived to him miss-wired regarding cables polarity.

Well I did steal the pictures because expert eyes they can see much more product Assembly problems than just wrong polarity at power cables.

For example PCB it self this is half in size that what it should be used, metal housing inside has signs of rust, direct soldering over banana screws, generally speaking only a blind person it would feel good paying close to 100$ USD for eight banana plugs, plus one meter length of cable.  :P

My estimate of production cost in China (MFJ-1117) this is approximately at 2,20 USD 


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36
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 % 

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

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.
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 even 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.  :-X
 

37
Bench-top multimeter / 10 milliohm shunt - Fluke 80J-10 100mV at 10A AC/DC
« Last post by Kiriakos GR on June 02, 2019, 05:06:18 PM »
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.
 
38
From time to time I do some thoughts about making my own PT100 simulator.  :)
Still I am undecided.

Even so I do collect ideas scattered worldwide regarding quantity of testing values.
Below it is a good example regarding measuring (testing range). 
39
Few days ago I did take apart few laptop battery packages, so to salvage any still working Lithium cell.
And I discovered one special component soldered over the BMS board, this is a Current Sense Vishay Dale 10 mOhms R01F resistor.

1W (6.35mm x 3.18mm)  ±75ppm/°C  Operating Temperature -65°C ~ 170°C 

First thought which I did was to rescue it by transferring it at another PCB, then I did discover it tight tolerance and build quality characteristics, this is a high quality 1W Current Sense!
Then I did concluded that best use for such a resistor this is to convert it to another calibration inspection gadget of ITTSB Blog. 
It is known that surface mount components cannot be inspected with any sort of Kelvin clips.
Therefore I did solder it over copper contact points (spacers) and I did recover compatibility with  Kelvin clips. :)

This is now my first (free of charge - Quality Sample) for further more upcoming Resistivity benchmarks.   8)
   
40
Keithley Model 2750:  Multimeter/ Data Acquisition/ Switch system.

Keithley Model 2750 this is a member of Keithley Integra series (Year 2003).

Keithley 2750 this all these years it was and is looking as invisible, because Keithley hide it in to a promotion catalogue of Switch systems.
At 2018 several of Keithley 2750 they shown on German eBay and several months back I did this discovery when I was looking for a used benchtop multimeter.
 
Keithley 2750 this is from the few benchtop multimeter this having low resistance range of 10 Ohm.
Accuracy specifications’ delivered by Keithley they are confusing as they mention ppm units comparison instead of percentage.

I found such a DMM in the price of less than 400 EUR with out scanner cards, and wasted a month time of research so to collect any available information’s, and my discovery was one MS-Excel plug in as data logging software and also the fact that Keithley this is hostile regarding calibration pricing or about delivering spare parts to customer hands.

While I came extremely close to get it, I did an 180 degrees turn and this later proven as wisest choice I ever made, because I am now much happier with my used 8846A which this has spare parts availability, and most Fluke authorized resellers’ they will help you getting them. 

Keithley Model 2750 this also hiding another risk as used :  Keithley updated it firmware several times and recent firmware cannot be used at older hardware revisions. :P

Now back then which I did my inquiry, what was impossible for me to find this was pictures of 2750 internals.
Today I was browsing German eBay used equipment's and I got lucky finding a 2750 with out it top cover and therefore here it is also your opportunity seeing what is inside.  :)

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