When is an Amp no longer an Amp? When it’s volted on soon in France.

[DougSpindler]

Anyone following this?  The definition of a Kg is changing which means the valuee of an Amp, Volt, Ohm, Watt and Kg as we know it will all change soon.

https://youtu.be/c_e1wITe_ig

[rhb]

I'm sure you'll notice the 0.1 ppm change immediately.  A *lot* of work went into linking Newton and Maxwell.  I  read about it occasionally over 10-15 years.  I think it's a major accomplishment for all concerned and I'm sure a source of great pride to have been part of it.

[DougSpindler]

I'm sure you'll notice the 0.1 ppm change immediately.  A *lot* of work went into linking Newton and Maxwell.  I  read about it occasionally over 10-15 years.  I think it's a major accomplishment for all concerned and I'm sure a source of great pride to have been part of it.

But isn’t the real question why has the weight of the kg (IPK) change?  Over the last 100 years or so the weight of the kg has decreased. 

[rhb]

The problem with a physical artifact is even if made of platinum, oxidation and  handling reduces the weight. It's unavoidable.  So there has been a long quest by the national labs to make the kilogram independent of a physical artifact.  This was first done by defining the meter in terms of the wavelength of light of a particular frequency a long time ago.  But the kilogram proved to be much more difficult.

Think about the fringing fields of an electromagnet. Those have to be accounted for *exactly* by an analytic solution of Maxwell's equations *and* you have to build a physical device which *exactly* matches the mathematical model.  I'd guess this took 100,000s of hours of work by the best metrologists in the world to accomplish.

In the ordinary world this is of no consequence.  But in standards lab level metrology it's a *really* big  deal.  This is a Nobel prize in physics accomplishment.

[tomato]

The problem with a physical artifact is even if made of platinum, oxidation and  handling reduces the weight. It's unavoidable.  So there has been a long quest by the national labs to make the kilogram independent of a physical artifact.  This was first done by defining the meter in terms of the wavelength of light of a particular frequency a long time ago.  But the kilogram proved to be much more difficult.

Platinum does not oxidize. Iridium oxidizes very slowly, but only at very high temperatures.  Even if they did, it would increase the mass, not decrease it.  Handling of the test mass also tends to increase the mass due to contamination. The most popular theory attributes the loss of mass of the kilogram to outgassing.

Think about the fringing fields of an electromagnet. Those have to be accounted for *exactly* by an analytic solution of Maxwell's equations *and* you have to build a physical device which *exactly* matches the mathematical model.  I'd guess this took 100,000s of hours of work by the best metrologists in the world to accomplish.

They don't calculate the magnetic field, they measure it; it's easier and more accurate.

[Housedad]

Our tax dollars at work.
Everything the lay person should know about the new SI change at the link below, courtesy of NIST.

https://www.nist.gov/si-redefinition/turning-point-humanity-redefining-worlds-measurement-system


An example of how kooky these folks are.  The ultimate volt/meter/kilo/watt/amp/frequency nuts.  LEGOs!!

[SiliconWizard]

This change looks like a huge step for some and we can probably applaud the accomplishment.

Getting rid of physical measurement standards and switching to theoretical formulas and constants is not without consequences IMO though.
What if we were wrong about the speed of light for instance? Damn.

[Mr. Scram]

What's this, thread number five on the subject? Yes, people have been following along. See the original thread and discussion below.

https://www.eevblog.com/forum/metrology/time-to-get-all-our-instruments-recalibrated/msg1971071/#msg1971071