Time to get all our instruments recalibrated...

[lewis]

[coppercone2]

don't make thread titles like that someone is gonna fucking die

[Rerouter]

Voltage changes by 0.1 ppm, he isn't wrong,

Every bit of equipment using the old constant value is consistent with themselves, but not to the top standard,

[Mr. Scram]

don't make thread titles like that someone is gonna fucking die

Never the subtlest of responses, are they?

The thread title is fully correct. Of course, as both scales should be fully linear they should also be readily converted.

[coppercone2]

you gotta break it gently, the thread title makes you feel like your entire life was a lie

Maybe its good that I never went more then 6.5 digits. Watch them argue about plank in a few years. 

better to live in a haze?

What if some fundamental constant changes because of shady goverment experiments in like The Quiet Earth? What if planks constant is found to oscillate or something as time elapses or as our galaxy moves through the universe or some other weird reasons  ?

[wraper]

Voltage changes by 0.1 ppm, he isn't wrong

Frankly it's not that significant even for 8.5 digit multimeters. They still will be well in spec. For example Keysight 3458A:

Extraordinary accuracy
– 0.6 ppm for 24 hours in DC volts
...
– 8 ppm (4 ppm optional) per year voltage
reference stability

[Mr. Scram]

you gotta break it gently, the thread title makes you feel like your entire life was a lie

Maybe its good that I never went more then 6.5 digits. Watch them argue about plank in a few years. 

better to live in a haze?

What if some fundamental constant changes because of shady goverment experiments in like The Quiet Earth? What if planks constant is found to oscillate or something as time elapses or as our galaxy moves through the universe or some other weird reasons  ?

The new definitions have been a result of our improved understanding of the universe and its nature, so redefining things even better once more would be nothing new.

[Edwin G. Pettis]

I just had my SR-104 certified to 0.15 PPM uncertainty.....I'm not worried.  Voltage standard is next soon.

[technix]

I think all 34470A are likely have to go back and recalibrate. The lower end gear... Maybe not so much,

[wraper]

I think all 34470A are likely have to go back and recalibrate. The lower end gear... Maybe not so much,

Why would they if the change is even outside of the last digit of 24h accuracy spec?

24 hours TCAL ± 1 °C
10 V 0.0025 + 0.0004

0.1ppm = 0.00001%

[Henrik_V]

Watch the livestream
Witness a historic moment; join an open session of the General Conference on Weights and Measures (CGPM)
considering the revision of the SI – including redefinition of four of the base units

https://www.youtube.com/thebipm

NOW

[technix]

The vote is on.

[technix]

The vote is done, and the resolution passed unanimously. New SI effect May 20 next year.

[BrianHG]

[0culus]

So is there a straight source that actually lays out who is affected by this? Is it only really high precision equipment? Or is my life a lie? 

[Kleinstein]

The changes are so small, that only the highest precision instruments are effected. At 0.1 ppm change this might be just noticeable with a larger set of of well maintained 734 or similar references - so maybe the larger national labs, but not the usual instruments like 3458 or fluke 8508.

If in doubt one just keeps track the the old cal was still due to the old SI. So nothing to worry about.

[mycroft]

https://xkcd.com/2073/

[apis]

From what I understand: since the change is because of a redefined constant you don't need to re-calibrate, just re-adjust all instruments where it might matter. The troublesome part will potentially be trying to figure out if an old measurement you read about in the future is referring to the old volt (or ohm) or the new one if it matters. Takes effect 20 May 2019.

[grizewald]

https://xkcd.com/2073/

Death to Imperial measurements!

A gallon? WTF!

In the UK, 4.5 litres. In the USA, 3.8 litres!

If people can't even agree to have the same meaning for a shared unit; just give it up and go metric, please?

Also, most people don't have 12 fingers. 12 inches to the foot? 

Maybe we should specify the speed of light as 1.8026×10¹² furlongs per fortnight?  Or buy fuel in millihogsheads? 

[JoeO]

You are half a world away.  Why do you care?

[Mr. Scram]

You are half a world away.  Why do you care?

Yes, it's not as if data and technology gets shipped across the world at near light speeds.

[RoGeorge]

Better recalibrate. 
In Ancient Egypt, death was the penalty for uncompliant instruments, and they were recalibrating monthly, not like us!

Very good talk about metrology:

[001]

don`t worry about kilogram whilst holy pounds and gallons are ok

[fsr]

https://xkcd.com/2073/

If people can't even agree to have the same meaning for a shared unit; just give it up and go metric, please?

Seriously, using the same unit of measurement, scaled by multiples of 10 is so convenient!
I know that habits are difficult to change, but using inches, feets, yards, miles with some "random" conversion factor between them must be a pain in the ass.
Just imagine that instead of having kV, V, mV, uV you have 4 different units to measure the same thing, with different conversion factors between them. Not very convenient!!

[coppercone2]

it's already like that with digital readouts on some calipers. If you work in imperial you can get fractional readouts. I think its a complete mess when you start getting to 32nds and beyond.

Yea imagine your multimeter told you some shit like 3 and 5/16ths of a milivolt and 43/83's of a microvolt. 

I wonder when they will fix thermal units........

[IanB]

Seriously, using the same unit of measurement, scaled by multiples of 10 is so convenient!

Indeed.

I know that habits are difficult to change, but using inches, feets, yards, miles with some "random" conversion factor between them must be a pain in the ass.

It is. So in general people don't do that.

Just imagine that instead of having kV, V, mV, uV you have 4 different units to measure the same thing, with different conversion factors between them. Not very convenient!!

What people do is take a suitable base unit (inch, foot, pound) and scale it by multiples of 10.

Engineers use inches and thousandths of an inch: "This part is 0.326 inches thick (326 thou)." Or they use pounds and thousands or millions of pounds: "The flow is 5.7 million pounds per day (5.7 MMlb/d)."

Broadly speaking, once a base unit is chosen all measurements are expressed in that base unit. You don't jump around.

Granted, doing calculations with mixed quantities is nowhere near as convenient as SI and lots of numerical constants get involved. I always prefer to do my calculations in SI and try to stay away from US customary units. But engineers who are familiar with customary units don't have trouble with them. It's just like learning to speak in a foreign language. Who would voluntarily want to speak German with its complicated grammar rules? But millions of people do and are fine with it.

[grizewald]

I grew up in the UK at the time when metric measurements were being introduced. Consequently, I learned to use both and have that innate hand and eye feeling for pounds, kilogrammes, pints and litres.

Regardless, I still think the Imperial system is an anachronism that should be assigned to the annals of history.

[Kleinstein]

The imperial units are also effected by the change. They don't have a separate pound artifact, but just an odd number one the calculator. At least with amps and ohms they use the SI units anyway - no more stat. volts or US ohms.

It's already quite some time the US changed over to metric inches. So it's only the second step that is missing.

Those fractions are odd: I like most the 355/113 of an inch.
Even worse than fractional inches are number drills.

[intabits]

I like most the 355/113 of an inch.

Me too.
It's by far the best simplest approximation to that irrational number using a rational number.  (I've checked)
Good to 7 significant digits, versus 22/7, which is only good for 3.

[coppercone2]

The imperial units are also effected by the change. They don't have a separate pound artifact, but just an odd number one the calculator. At least with amps and ohms they use the SI units anyway - no more stat. volts or US ohms.

It's already quite some time the US changed over to metric inches. So it's only the second step that is missing.

Those fractions are odd: I like most the 355/113 of an inch.
Even worse than fractional inches are number drills.

i think they are letter drills too


Yea, imagine having all those drills, in metric, imperial, letter and number along with the respective reamers. Oh yea in stub and long. And then all the taps. 

[apis]

It's just like learning to speak in a foreign language. Who would voluntarily want to speak German with its complicated grammar rules? But millions of people do and are fine with it.

Good analogy.

Many of us are voluntarily not using our native language here on the forum. Why is that? It's because using the same language makes life much easier for everyone. Instead of forcing everyone to learn all the languages of all the members of the forum we use English as a de facto standard.

In the past every city used their own definition of all the units, but now we have a global standard that everyone (except the USA) uses because it makes life much easier for everyone when communicating.

[apis]

The imperial units are also effected by the change. They don't have a separate pound artifact, but just an odd number one the calculator. At least with amps and ohms they use the SI units anyway - no more stat. volts or US ohms.

It's already quite some time the US changed over to metric inches. So it's only the second step that is missing.

Those fractions are odd: I like most the 355/113 of an inch.
Even worse than fractional inches are number drills.

i think they are letter drills too

Yea, imagine having all those drills, in metric, imperial, letter and number along with the respective reamers. Oh yea in stub and long. And then all the taps. 

Technically, that has little to do with SI though. There is no reason you couldn't use fractional meters or fractional micrometers, and you could have all kind of different drill, tap, tread, wrench, wire size standards that all were based on SI. But the problem is the same, it's more convenient if everyone could settle on one standard when possible.

[IanB]

Many of us are voluntarily not using our native language here on the forum. Why is that? It's because using the same language makes life much easier for everyone. Instead of forcing everyone to learn all the languages of all the members of the forum we use English as a de facto standard.

In the past every city used their own definition of all the units, but now we have a global standard that everyone (except the USA) uses because it makes life much easier for everyone when communicating.

It's true. And I never voluntarily use US customary units for any calculations since they are a royal pain in the behind. (And I am not American, so I have no cultural need to use them.) I do however understand them, and I can comfortably follow along if other people use them.

[branadic]

Yea imagine your multimeter told you some shit like 3 and 5/16ths of a milivolt and 43/83's of a microvolt. 

I wonder when they will fix thermal units........

I would be happy if they would be aware of elementary unit such as milli, micro, nano, pico, femto atto, ... and also in the other direction, too. By now they don't.
I always wondered about their power of ten counting as well: million, billion, trillion, quadrillion instead of million, milliarde, billion, billiarde, trillion, trilliard, ... It's kind of weird and inconsistent in itself.

-branadic-

[e61_phil]

I always wondered about their power of ten counting as well: million, billion, trillion, quadrillion instead of million, milliarde, billion, billiarde, trillion, trilliard, ... It's kind of weird and inconsistent in itself.

Isn't it more straight forward than our way of counting?

million first
bi...
tri...
quad..

and after that

pentillion
hexillion
septillion
octillion
ennillion
 


sounds reasonable

[fsr]

Giga dollars, tera dollars. Problem solved

[Svgeesus]

Engineers use inches and thousandths of an inch: "This part is 0.326 inches thick (326 thou)." Or they use pounds and thousands or millions of pounds: "The flow is 5.7 million pounds per day (5.7 MMlb/d)."

No, engineers use SI units: meters, millimeters etc. Everywhere.

With the sole exceptions of Liberia, and USA. (Myanmar, formerly Burma, changed from Imperial to metric in 2013).

[intabits]

Great chart!
But:-
1 NM = 3ft x2 x100 x10 = 6000ft <> 6080ft as shown? (And is now defined as 1852m =  6076.115ft )
The factors 3 and 2 are not in any doubt at all, the 10 seems to be rigidly defined for cables/NM, so the slop is in the 100 for fathoms/cable...

[coppercone2]

Engineers use inches and thousandths of an inch: "This part is 0.326 inches thick (326 thou)." Or they use pounds and thousands or millions of pounds: "The flow is 5.7 million pounds per day (5.7 MMlb/d)."

No, engineers use SI units: meters, millimeters etc. Everywhere.

With the sole exceptions of Liberia, and USA. (Myanmar, formerly Burma, changed from Imperial to metric in 2013).