4 Wire DMM Shorting Plug - Mini Review 5/2026 - Made in Italy - eBay

[Kiriakos GR]

When you get close to electrical metrology, two things they might happen.
You might find it as boring and walk away, and or find it as interesting and you do get inspired by it.
Getting Inspired this is nice, but it creates also and another responsibility, of you to study the work of others,  otherwise you are not able to follow and or to understand of how the theory this transform’s in to praxis, when you do perform performance verification tests at one high precision instrument.

Mr. Claudio from Italy, he is one of us, which we got inspired.
And today I am extremely happy, because samples of his own work, they arrived in Greece for a road test.
Mr. Claudio, he when at his technical drawing board, so to design his own version, of four wires calibration SHORT, for distribution within European union.

The product consists of:
1x OSH Park (After Dark) PCB, with ENIG finish or JLPCB with ENIG fin.
4x Staubli SA403 22.1053 4mm Plug
4x Staubli nut 22.6509
1x 3D printed nylon PA handle (MJF) JL3DP + fastening screws.

The two PCBs only differ in the mounting holes (4 or 2), the different surface finish, and the silkscreen.
The measurements and tolerances of the copper traces are identical, as is the ENIG finish (theoretically...).

Mr. Claudio offered to me free samples of both versions.

Testing of such samples, this has never been made in public view before.
All representatives of official electrical metrology, while they do use such a 4W SHORT Plug, they never documented enough the in-depth theory behind of this accessory electrical design.
In simple words, this item it should represent the Ideal Zero Ohms resistor, when a precision multimeter this is tested for performance verification at 4W resistance mode.
These were my thoughts too, prior reading five service manuals about high precision DMM that I do not own.
   
4W SHORT Plug this is product design of 80s, over the decades it uses for it has been changed, and later on the fully automated calibrators, they do simulate a Zero Ohms resistor.
What the modern calibrators cannot do, this is removing any charge caused from 1000V calibration verification test, from the inputs of the DMM.
In a true calibration lab, the use of 4W SHORT Plug, this is for removing even smallest electrical charge stored at DMM inputs.
Next steps of calibration testing, at 100mV range and or at 4W resistance, they can happen, when the instrument this is not influenced due parasitic charge.

Over the years, such a 4W SHORT Plug, this has different uses for us consumers.
I represent the group this performing performance tests, in order to find out, if there is any electronics component failure within the instrument.
Inspection of noise floor and other details, they are parts of my own testing process.

I own the FLUKE 8846A, this under the hood, it represents a metrology class of an instrument.
According to FLUKE Calibration mindset, 8846A this was designed to be the small brother of 8508A Reference multimeter.
8846A and this 8508A Reference multimeter, they have a special function in common, this is named as RATIO at DCV mode.
This implementation of RATIO, this is based at 100% hardware level.
Because of this function, the 8846A it can measure reliably the difference of two voltage sources, down to 1ppm at 100mV DC range.
This 1ppm corresponds to resolution of 100 nV.

Anyone involved at replicating such a 4W SHORT Plug, he is well aware of the biggest challenge than all.
He should design an item, and use best Low Thermal materials, so the outcome to be near to Zero generation of EMF.
Otherwise the 4W SHORT Plug, it will look like at the multimeter inputs, as this is a miniature of a DC battery.

My 8846A, in combination with PC data log software TsDMMViewer, this is a powerful setup, I can data log RATIO mode, and the PC it provides the memory and the clock.
The sum it is equal building a High resolution TREND Plotter.
 
ITTSB.EU 4W SHORT Plug testing process
1) I use RATIO mode, so my 8846A alone, this to measure and decide which of the two products, this is a smaller EMF battery. 

2) I use 4W resistance mode 10 Ohms range, with REL active so I to record noise floor levels. 

3) I use 1V DC range at 8846A, so I to record noise floor levels.
4) I use 10V DC range at 8846A, so I to record noise floor levels.

In summary I have to offer and or to share today, collected statistics, from my very own High resolution TREND Plotter.
And I do dare calling it as my own, because I earned my stripes, by assisting and collaborating with the software developer in Japan, for about three months.
I am the one which inspired him, so him to get involved, at expanding the compatibility of his software with bench top multimeter.
Previously his software this were supporting only HH DMM data log.

This month, the work of Mr. Claudio from Italy, this inspired me and motivated me enough, so I to discover more knowledge, this coming from a dedicated sector at electrical metrology, this named as low power electrical metrology.
 
While my starting point this is a graduated electrician, I did improve my metrology related training all by myself, due my passion so to discover and understand more segments from this science.
My own test results, they are proofs of what electrical metrology enthusiast’s they can achieve, by collaborating together and by joining forces.
 
Those 4W SHORT Plug’s, production of Mr. Claudio from Italy, they are available on eBay.
Store name: swan997
https://www.ebay.com/usr/swan997


Qualifying registered forum members’, they have also the privilege of a direct feedback exchange with Mr. Claudio.   
He was inspired, after the purchase of an Agilent 34401A.
It’s upon his own will, if he will share more in public, about his own thoughts and motives.
My own responsibility, this is limited to offer a well-made presentation, so and I to justify my title within ITTSB Blog, as technical content creator. 

For a first time, I will leave the flow of recorded logs in the form of screenshots, at my mini review so these be the proofs of product design success !!

[Kiriakos GR]

I use RATIO mode, so my 8846A alone, this to measure and decide which of the two products, this is a smaller EMF battery.
This is actually thermal offsets detection and comparison, and or (Johnson noise) of the DUT materials.

The software developer of TsDMMViewer he owns 8846A old rev, with 100mA current input.
This revision does not support RATIO, and we neither though adding RATIO specific prefixes in the software.
Even so the software works, displayed units this is not mV but Milli-units at eight decimal places
Physical display this can deliver six decimal places resolution.

For 8846A and RATIO mode there is a fresh specific topic.
https://www.ittsb.eu/forum/index.php?topic=2315.0
       

[Kiriakos GR]

I use 1V DC range at 8846A, so I to record noise floor levels.

I use 10V DC range at 8846A, so I to record noise floor levels.

[Kiriakos GR]

I use 4W resistance mode 10 Ohms range, with REL active so I to record noise floor levels.


Note: This period of time, Mr. Claudio he is working at making an step up version of his previews work.
I wish him from my hart, good success !!!

And it will be my pleasure, to offer my own feedback again and in the future, if he needs it.
The Hellenic electrical T&M lab of ITTSB Europe, this is always available assisting Europeans them powered by increased inspiration.

[Kiriakos GR]

About my own testing I feel the need to offer one additional clarification, regarding testing conditions.

At bench top multimeter with 19,05 mm banana inputs spacing, any compatible SHORT, this will include PCB lines, these forming an electromagnetic waves RF antenna.

There is a theorem this coming from RF applications, 19,05 mm length this represents the wavelength of 4 GHz (3997 MHz), and the obvious polluter at this frequency this is Wi-Fi communications in the form of interference due harmonics.
While main frequencies’ these are 2.4GHz and 5 GHz for Wi-Fi.   

At the time of my testing, I had switch my mobile phone at 2G band, Wi-Fi on the phone this were disabled.
My very own Internet and Wi-Fi router, this is placed three meters away from my 8846A, and there was no Wi-Fi activity.

My advice for anyone interested to perform similar tests as I did.  Keep in a safe distance of three meters away, any device this is active as RF transmitter.
       
Similar precautions, they should be taken by anyone using such SHORT plugs, because specific product design it’s not shielded against RF pollution.

About eight years ago, I become aware, that most calibration labs, they are using underground laboratories, for two good reasons.
As first, retaining of stable room temperature this is easier to maintain at underground laboratories.
As second benefit, there is no RF signal penetration, at underground laboratories.
They can use long length of cables, without fear of RF noise pollution.
Additionally all verification of electrical standards stability, this is also happens at underground laboratories.

I am performing my testing at regular environment, and I am aware of it limits.
For example if my data log this include a few spikes, this is not a proof of a major issue.