Today I was working in the lab with my German friend, and we were dealing with a gas cylinder with pressure labelled in pascals. He commented that he doesn't like pascals because in Germany they use millimeters of mercury.
There you have it. The United States tries to metricate in order to match their units to other countries, using the official SI guidelines, and other countries are using something else.
FYI the cylinders are also marked in psi.

I've only ever noticed pressure marked in PSI.

If you go to a petrol station in the UK the airlines are marked up in PSI

The official positions re garding the measurement of pressure in Germany are:

SI recomendations - pascals (preferred), bars (permitted).

EU (for all legal, economic, public health andpublic administration purposes) - pascal or bar are mandatory except for the measurement of blood pressure or the pressure of other body fluids where mm Hg are permitted.

Bud - unless you colleague was working in the medical field, he was not following recomedned German practice.

Martin, I am not familiar with Germany, but I cannot imagine that German engineers would be any more willing to change their units upon instructions from the government than anyone else. I view any recommended practices of this sort as idealized and very desirable in theory but usually incompatible with current practice and therefore ignored.

I took a tour of a place called Teneco Automotive, they make mufflers, and they metioned 1000 Bar of pressure. They also mentioned their machinery was from Germany. I take it that Bar are not official SI units. Is this true? Is Bar a remainent of the MKS metric system? Does anyone know of any other non official SI units that Germany uses?

The bar is a multiple of the official SI unit, and thus fits into the SI system quite nicely. Just because there is no prefix for 10^5 doesn't mean that it cannot fit into the system like any other multiple.

Well I wish my school would have told me that. Thanks for the info though.

"Does anyone know of any other non official SI units that Germany uses?"

Along with the rest of the metric world: km/h

It should be m/s

(There's that fire stoking again.....)

The International System of Units (SI) has various groups of units:

1. The seven SI base units – the metre, kilogram, second, Coulomb, Kelvin, candela and mole.

2. The seventeen SI derived units, which include the Newton, Watt, Joule, Farad, Gray etc.

3. A set of ten units based on SI but which are not strictly part of SI, but which the CGPM (the governing body of the BIPM)recommend as being suitable for use with SI. They include the day, hour, minute, litre, tonne etc.

4. A set of three units that are derived experimentally (the electron Volt, atomic mass unit and astronomical unit).

5. A set of seven units including the are, hectare, bar and knot which can be used in conjunction with SI, but on which the CGPM are reserving judgement

6. A set of old metric units including the erg, Maxwell and Stokes which are now obsolete and which should no longer be used.

The astute reader will notice that eight British scientists or engineers (Kelvin, Newton, Watt, Joule, Faraday, Gray, Maxwell and Stokes) have been honoured by having units of measure named after them.

As far as I am aware, all German units in everyday use comply with the above list.

so much for metric simplicity.

It seems to me that the people who came up with the above regulations made them in order to lay down the units that they want to be used, but then stretched them to include other units that are commonly used in metric countries, i.e. units that they have no hope of abolishing. How else can you explain that knots (nautical miles per hour) is on the list?

Martin, would you happen to know what the other three units are for point 5?

Re: lab May 12 2004, 9:11 PM


so much for metric simplicity.

metre:
Says a man defending the most cumbersome system. Should I bring you some imperial examples that make your hair stand on end?

<<
Says a man defending the most cumbersome system. Should I bring you some imperial examples that make your hair stand on end?
>>

I think you've brought in enough.

Bud wrote

<<
Martin, would you happen to know what the other three units are for point 5?
>>

Bud, the information is available on the BIPM site - www.bipm.org. Find the link to the PDF file that contains the formal defintion of SI.

Will someone pleeeeease give Eric a rattle to play with?

Reading the formal information on SI on the BIPM website, I realize that the SI system is even more rigid and unflexible than I thought. And I think that document has been written in a rather authoritarian tone.

Bud, while the SI document might be "authoritatian" in nature, you should also bear in mind:

1. It takes many years for new definitions to be accepted.

2. It is designed to enable people from different cultures to communicate in an unambiguous manner.

3. It is designed so that Governments can use it as it stands as part of their own law.

Re: lab May 13 2004, 8:04 AM


<<
Says a man defending the most cumbersome system. Should I bring you some imperial examples that make your hair stand on end?
>>

I think you've brought in enough.


metre:
Obviously not enough for you to see the light.

Re: lab May 13 2004, 3:02 AM


It seems to me that the people who came up with the above regulations made them in order to lay down the units that they want to be used, but then stretched them to include other units that are commonly used in metric countries, i.e. units that they have no hope of abolishing. How else can you explain that knots (nautical miles per hour) is on the list?


metre:
Well, who forced the metric world to use knots for aviation? Apart from that its only used for maritime purposes.

"Well, who forced the metric world to use knots for aviation"

The same people who forced it to use feet.

"Apart from that its only used for maritime purposes."

Actually it's frequently used for wind speed measurements.

From Martin:
<<
The International System of Units (SI) has various groups of units:

1. The seven SI base units – the metre, kilogram, second, Coulomb, Kelvin, candela and mole.

2. The seventeen SI derived units, which include the Newton, Watt, Joule, Farad, Gray etc.

...
>>

The units in category (1) are a fundamental and complete set that can be used to describe the physical world and provide a basis for all calculations in physics and chemistry.

All other units are superfluous in that they add nothing that cannot be expressed in units from that set of 7.

e.g. The Newton can be axpressed as 1 kgms^-2.

It would however be cumbersome to do this and so the 17 derived units in (2) have been added.

Metric prefixes are not strictly necessary if exponential notation is used, e.g. 1E6 W instead of MW.

Again they exist for convenience.

The symbols and rules of expression in SI are carefully crafted so that they are unambiguous, language independant and minimises the number of characters required whilst remaining human readable.

In short that part of SI is the most rational and complete system of measurement ever devised.

The remaining units listed in SI are there to standardise them and to give them unique symbols. They have been included on the basis of common International usage.

The knot is included because of common maritime and aviation use which is subject to International agreement.

Units like the pint and gallon for example are excluded because of regional variations.

However certain other units like km/h are not listed because they don't need to be. They are self explanatory and, if written as in the foregoing, follow SI conventions (i.e. not kph). If the SI listed every conceivable compound unit with definitions that are obvious from its symbols, it would degenerate into an Xcole type document.

<<
In short that part of SI is the most rational and complete system of measurement ever devised.
>>

Far more rational and complete than necessary.

Re: lab May 18 2004, 4:26 AM


<<
In short that part of SI is the most rational and complete system of measurement ever devised.
>>

Far more rational and complete than necessary.


metre;
What an outlandish statement, sounds like you felt compelled to say something sensible, or not. Rationality is like pregnancy, no woman can be a little pregnant.

To Stan

Thanks for contributing a well thought out, accurate and discussion-worthy entry from a pro-metric point of view to this thread. It was a refreshing change.

And well overdue.

SteveH

Chief troll starver, pro-choice division

I've just installed a nice new 27" by one and a quarted" tyre on my bike. Just to shew (sic) I'm a good European (as my passport used to say) I didn't baulk at the fact it was made in France.

HOWEVER i note that the old one had (parenthetically) that the tyre should be inflated to 445kPa after the 85psi. Nearly half a million pascals eh? Sounds a lot. However the new Michelen one only mentions good old englsh. Make me smile anyway.

WARNING.
I was given a tyre professing the measurement 700c. Upon calculation i worked out that this should be fine as it's should have been 1/2" bigger than my 27" tyre. However after much pulling and cajoling it just wouldn't go on. It must be measured somewhere else. No point standardising measurements if you don't standardise what you're measuring. To coin a phrase 'METRIC ISN'T WORKING"