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The Tale of the Cold Shack and the Hot Body

from Peter Gant, DL8OV on May 6, 2019
View comments about this article!

Physics in Action -- The Tale of the Cold Shack and the Hot Body

Somewhere near Paris, France there is a room holding the original standard metre. It's a long metal rod supported at multiple points and kept underneath a glass cover. The room is lit by fluorescent tubes but, in the middle of the room, are three lit 100W incandescent light bulb that are essential to the operation.

Why?

If someone wants to compare their metre to the standard they walk into the room with an assistant and immediately turn off two of the 100W light bulbs, they then make their measurements and, before leaving, turn the two light bulbs back on. Humans, being warm blooded, generate a certain amount of body heat, even when at rest, for men it's about a hundred and twenty watts and for women it's just under a hundred. Sure, the temperature in the room is tightly controlled, but two people walking in are a sudden source of two hundred watts of heat and by turning off the two light bulbs the status quo is restored. It's a simple system and it works well.

Some time ago I purchased a GPS locked 10 MHz frequency standard. It's one of these things which you plug in and forget about as it just sits there in the shack providing a 10.0000000 MHz timing signal for the spectrum analyzer, the signal generator and the frequency counter. The frequency counter also has a TXCO, not as good as an oven controlled device but good enough for most measurements if I am out of the shack.

It's now Winter here in Germany and I have the radiator in the shack on 24/7 to generate an approximate 20C, and I do mean approximate here! With the TXCO controlled counter on for two days to ensure stability I see a measurement of 9.99999997 MHz when the GPS locked oscillator is connected. Sit down in my shack chair with no other equipment powered up and I can see the display slowly increase to 10.0000000 MHz over a thirty minute period. This behavior is repeatable and I have seen this happen for the last four days, an error of a tiny fraction of a Hertz that is corrected by body heat as I warm the shack up just a little by sitting there.

Isn't physics fun!

Happy New Year!

Peter DL8OV

Member Comments:
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The Tale of the Cold Shack and the Hot Body Reply
by W0WCA on May 6, 2019 Mail this to a friend!
Yes, it is; very nice piece!
 
The Tale of the Cold Shack and the Hot Body Reply
by N8AUC on May 6, 2019 Mail this to a friend!
What this illustrates, is that when attempting to achieve extreme precision, one must pay close attention to even the smallest details.

Interesting that your body heat in the room causes a 3Hz difference in the frequency of a precision oscillator. Now that translates to a 0.3 PPM error, which is extremely small. But it's far greater than zero.
 
The Tale of the Cold Shack and the Hot Body Reply
by K6CRC on May 6, 2019 Mail this to a friend!
Interesting story. I worked near a metrology lab in my first job out of college. I remember the old time tech using weird and wonderful stuff to calibrate customer test equipment. He told me once in the coffee break room they would calibrate in the afternoon, then re-check the next morning before boxing it up. Didn't make sense then, and I didn't bother to ask why. I can see why now.
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by K9MHZ on May 7, 2019 Mail this to a friend!
You should start it right at 10 MHZ, and then guzzle cold Kolsches to see if your oscillator can keep up. You might be a hit at the local pub.
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by AA4MB on May 7, 2019 Mail this to a friend!
"Interesting that your body heat in the room causes a 3Hz difference in the frequency of a precision oscillator."

Actually, it would be a .03 Hz difference, right? Still interesting that the difference is readily measurable. My head now Hertz from all of this math.

- Matt, AA4MB
 
The Tale of the Cold Shack and the Hot Body Reply
by DL8OV on May 8, 2019 Mail this to a friend!
I should add that this story was sent to Eham a few months ago in the depths of a German winter.

Peter DL8OV
 
The Tale of the Cold Shack and the Hot Body Reply
by VE3KKQ on May 8, 2019 Mail this to a friend!
Should anyone desire to learn more about metrology, electrical, electronic measurements and standards or if you need something to read in bed while having trouble getting to sleep, I highly recommend this book from the Fluke company, "Calibration: Philosophy in Practice".

www.introni.it/pdf/Fluke%20-%20Calibration%20Philosophy%20in%20practice.pdf


Or if you are quit flush, buy it.

John
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by N4UM on May 10, 2019 Mail this to a friend!
Is this another example of the Heisenberg Uncertainty Principle where the act of observing an event changes the very event one is trying to observe?
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by K9MHZ on May 10, 2019 Mail this to a friend!
"...where the act of observing an event changes the very event one is trying to observe?"

After a few Kolsches, it would be the same effect for Peter. Girls in the pub will dig him, too. Far more interesting with them. Hanging with physics guys or blonde German women....what to do, what to do?
 
The Tale of the Cold Shack and the Hot Body Reply
by DL8OV on May 11, 2019 Mail this to a friend!
Glad to see that my piece is finally inspiring some thought. I did consider the Heisenberg issue and the only solution I could think of was a delayed trigger on our camera, perhaps taking a picture of the counter display every thirty minutes without me being in the shack. It is however now far warmer so the experiment will need to wait seven months or so.

The heating has been off for some time and the outside temperature is about ten degrees warmer than when I wrote the article. This means that the displayed frequency has gone up by twenty millihertz to 9.99999999 MHz and when I sit down in the shack it gradually climbs to 10.0000001 MHz, close enough for government work.

Peter DL8OV
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by KB6QXM on May 11, 2019 Mail this to a friend!
Close enough for who's government work?
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by K9MHZ on May 20, 2019 Mail this to a friend!
^^^ Funny!
 
The Tale of the Cold Shack and the Hot Body Reply
by K5HEC on June 2, 2019 Mail this to a friend!
That is INTERESTING! Us hams are different ... I don't operate too much but I like to hang out with such people.
 
The Tale of the Cold Shack and the Hot Body Reply
by K5HEC on June 2, 2019 Mail this to a friend!
Germans love the fresh air. I lived in Paris for a year. The French liked their space to be close and warm. The Germans liked their curtains flapping in the wind and the air as fresh as Paris could provide. German radios probably last longer.
 
The Tale of the Cold Shack and the Hot Body Reply
by W8LV on June 12, 2019 Mail this to a friend!
To solve ANY Scientific problem,
all you need are three things:

A chalkboard,

A piece of chalk.

And one German.

;-)

73 DE W8LV BILL
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by K9MHZ on June 13, 2019 Mail this to a friend!
In a Starbucks there right now. Trust me, the Germans have even more going for them than physics and BMWs. Blonde, blue eyes, and well, you get the idea. And if she likes physics or ham radio (Funkradio), you may never go back to the land of Walmart.

Forewarnings are always good.
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by K9MHZ on June 13, 2019 Mail this to a friend!
Oops, make that “Funk Amateur” magazine. Should have gone to the bookstore first. Next month’s issue will feature the IC-9700, I think. Nice pictures in that magazine, muddling through the translation takes a little time. In the U.S., “Funk Amateur” would mean something totally different....usually seen/smelled at a hamfest.

Friedrichshaffen (sp?) is on the bucket list. Beers afterward at Peter’s place.
 
RE: The Tale of the Cold Shack and the Hot Body Reply
by W8LV on June 16, 2019 Mail this to a friend!
4 to 1 odds that the Europeans will get Fusion right.
2 to 1 odds that The Team will be chaired by a German.

The Dark Horse? A Canadian, who is very, very close.
All it takes is Funding.

And who knows? The Americans might have sequestered a team of Scientists in some remote location who are working day and night on the problem. That's been known to happen before! And some of them might be reading this right now from that very location, hooting and hollering from their desks! When Americans DECIDE that they are going to the Moon? Well, they go to the Moon. I just wish that they had that kind of will when it comes to say: Public Transportation.

The Coffee Shop Take Home?

What did both the American and Soviet Space Programmes have in common? That both of the countdowns were in German!

Disclosure Statement: My last name is Pietschman. As in "Americanized" from "Pietschmänn"...
I'm an American. And my affection for BOTH Team America AND Team Canada run VERY deep!


73 DE W8LV BILL


 
The Tale of the Cold Shack and the Hot Body Reply
by KC1VY on June 16, 2019 Mail this to a friend!
That is neat stuff ! Thank you for sharing that. The physics,mathematics and thought experiments that go along with that is fascinating. Black body radiation, ultraviolet catastrophe, laws of thermodynamics,etc. well it's just fascinating !!
 
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