really idiotic, even by EE Times standards

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John Larkin         Highland Technology, Inc 

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John Larkin
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Why do you object to a new method that will facilitate measuring temperatures more accurately and with less systematic error?

The old standard based on the triple point of water was always a bit iffy with the calibration always depending on the quality of the water and its isotopic composition. Never going to make any difference to basic engineering but it may have surprising applications elsewhere.

Time and length are already very well standardised.

Mass is still a bit iffy and the "standard reference kilogramme" is gradually losing mass (or the copies getting heavier).

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Regards, 
Martin Brown
Reply to
Martin Brown

I think John is objecting to the article suggesting practical and "inexpensive" applications of an exotic laboratory technique when the author appears to be totally ignorant of the current state of the art (or even the 30-year-old PTS-90). And I'll go out on a limb and say nobody needs to know the temperature of a semiconductor die to "parts per billion" and even if they did, this method would not achieve it.

Josephson Junction voltage standards are exceedingly cool too, but I don't think we're going to be having them in our multimeters any time soon.

--sp

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Best regards,  
Spehro Pefhany
Reply to
Spehro Pefhany

Pretty idiotic, yup. Their "advanced technology editor" doesn't appear to know anything about SI, as he says that "the kelvin will be replaced by the SI." in other words he thinks that "SI" is the name of a new unit.

The actual science is potentially pretty interesting. The usual way to do that measurement is with four wires and two FET amplifiers with their outputs cross-correlated. I gather that there's more going on in this scheme.

Cheers

Phil Hobbs

Reply to
pcdhobbs

Another odd thing is, this can only be as stable as the resistor value; you need to use both the resistance AND Boltzmann's constant to produce the temperature.

So, why is the test resistance value independent of age, oxidation, strain, and local magnetic field?

Then, of course, the bandwidth of the Johnson noise measurement is critical to getting a good determination: what exactly is the character of the bandpass on that measurement? The NIST says they use a Josephson junction (AC) accurate V reference and DSP determination, differentially, to eliminate dependence on component values.

So, this is about a way to get (in a calibration lab) a lineup of exotic devices (including superconducting Josephson junction) and potentially add to the triple-point of water a dozen other known-temperature stations at different temperatures. There'd be a regular recalibration against that water triple-point, I suppose, for the sense resistors.

The test jig is amusing: the resistor is a four-wire device, with two leads being normal, and the other two having controlled-impedance to the external connector. it's similar to a Kelvin resistor, but with an extra design goal.

Reply to
whit3rd

It is definitely the sort of thing that only metrologists can get excited about but anything that ties down the calibration of a unit of measurement to the constants of nature has to be a good thing*.

(*) provided that the constant is determined to a decent number of significant figures gravity as in G is a bit dodgy there.

I recall that was a part II physics practical in the late 70's for those in the experimental stream. Great fun with the loop quantised staircase waveform and surprisingly accurate if they got it to work at all.

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Regards, 
Martin Brown
Reply to
Martin Brown

I didn't read your link, I assume this is the same Nist group that has been working on this for a while. I read previously that they have some multipole low pass. (7,9,11? I can't recall) and a lot of the work is getting a good model of the filter... (probably temperature dependent :^)

George H. The NIST says

Reply to
George Herold

What I thought was stupid was

"There is little doubt that the SI will replace the Kelvin as the international standard of temperature..."

which is wrong in lots of ways.

These EE magazines are mostly edited by journalism types who never learned the basics.

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John Larkin         Highland Technology, Inc 

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John Larkin

The first (or second) comment tries to correct this mistake. (And points out that you must integrate for days to get the accuracy... two days to measure the temperature of my FET, I don't think so. :^) But the author just blows it off.

George H.

Reply to
George Herold

I thought that was quite funny. Typical junk journalism.

But even learned journals are not above mangling key sentences in final drafts for publication such that a classic maximum entropy paper states "it cannot lead to conclusions for which there is evidence in the data".

An editor intending to clarify things removed the word "no" between "is" and "evidence". The authors vowed never to use a double negative again.

That is true of most editors though. Very few have significant scientific or engineering training and rely on external reviewers.

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Regards, 
Martin Brown
Reply to
Martin Brown

The first sentence says it all:

"Forget Kelvin, Fahrenheit, and Celsius, not to mention centigrade."

None are going away because of a possible metrology advancement.

Their only purpose is to sell ad space. They aren't very good at that, either.

Reply to
krw

No. The EE-type mags are literally disappearing, down to 30 pages or so. And full of idiotic editorial content. And why does Master Bond get so much attention? It's just epoxy.

The optics and microwave mags are doing fine, fat and glossy and full of ads.

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

Fahrenheit has been eliminated in all civilised countries.

Only knuckle dragging retards still use British (sic) units of measurement that have been preserved in aspic from around 1824.

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Insane US units conversions errors have been the downfall of more than one spacecraft and aircraft falling out of the sky for lack of fuel.

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Regards, 
Martin Brown
Reply to
Martin Brown

Martin, you cannot take away imperial units from the US. SI units are un- american, as well as metric screws. ;-)

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Reinhardt
Reply to
Reinhardt Behm

Fahrenheit has been eliminated in all civilised countries.

Oh, come off it, Martin. Celsius has half the resolution, equal accuracy, and its end points are no less arbitrary than Fahrenheit's.

Celsius is more convenient for calculations, but Fahrenheit is way better for the weather forecast.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

Are you suggesting that the Bahamas, Belize, and the Cayman islands are not civilised?

Celsius used the freezing point and boiling point of water as its limits (originally, boiling point was 0 and freezing was 100). Those are points that are simple and easily reproduced.

Fahrenheit used a mixture of salty water for 0 and "blood temperature" for 96 - as if that were a good, stable choice.

These days, Fahrenheit is /defined/ in terms of Celsius - that should give you a good idea of which scale is considered the accurate reference.

Fahrenheit is "better" for weather forecast only in the sense that people who are used to seeing the forecast in Fahrenheit find it easier to understand weather forecasts in Fahrenheit. Fahrenheit has no benefits or uses whatsoever that are not a direct consequence of the habit of using Fahrenheit.

Reply to
David Brown

How many European and Russian spacecraft have landed on Mars?

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John Larkin         Highland Technology, Inc 

lunatic fringe electronics
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John Larkin

So if we want to express temperatures more accurately in degrees Celsius, just add one decimal digit to the right of the decimal point:-)

The accuracy of forecasted temperatures is very bad compared to the actual measured temperatures, so why would a finer scale help ?

If I understood correctly, the US forecasts talk about low 60s and so on, thus a range of 5 F or 2 C.

In practice, when you drive from one suburb to an other suburb or from suburb to city center, the car outdoor thermometer shows similar size variations, so what is the actual temperature for a city or small area?

Reply to
upsidedown

Come off it again. Fahrenheit is currently defined in terms of Celsius. That's what I meant by "equal accuracy" above. Why would anyone want to maintain two standards that would just get out of sync?

What a crock. To be consistent with that argument, you'd have to advocate returning to the original definition of the metre, based on a surveyed quadrant of the Paris meridian--a line both of whose ends are way out to sea. (Like so many subsequent French initiatives, bud I digress.) ;)

As I stated above. Your point being?

Okay, you don't like it, which is fine. I'm a Canadian living in the US, so I'm used to it both ways without needing to convert in my head. I prefer Fahrenheit for its improved resolution, especially rhetorically. "the 60s" Fahrenheit is shirt sleeve weather with no air conditioning needed. "the 10s" Celsius ranges from a medium jacket to a golf shirt. See? Resolution is a good thing.

Except for the ones that I keep pointing out and you keep officiously blowing off.

You don't like it, is all. I have no quarrel with that--it's the idea that people with other ideas are somehow unscientific morons that I cordially dislike.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Reply to
Phil Hobbs

Yeah, good luck getting the weatherman to do that, or your digital thermometer--have you ever seen one that had more significant figures in Celsius?

It helps rhetorically a great deal, as I pointed out elsethread, I have a wireless digital thermometer on my house. Three digits either way, meaning that it's easier to estimate rates of change accurately.

You folks are just making apologies for an inferior scale, at least for rhetorical purposes. You like it, that's fine, but let's leave off with the idiotic condescension, as though anything European is automatically better. That's the sort of crap you folks accuse _us_ of.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

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