28.12.2013 Views

preface to fifteenth edition

preface to fifteenth edition

preface to fifteenth edition

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

11.138 SECTION 11<br />

of water which is defined <strong>to</strong> be 273.16 K. The Celsius temperature scale (C) is defined by the<br />

equation<br />

C K 273.15<br />

where the freezing point of water at 1 atm is 273.15 K.<br />

The fixed points in the ITS-90 are given in Table 11.39. Platinum resistance thermometers are<br />

recommended for use between 14 K and 1235 K (the freezing point of silver), calibrated against the<br />

fixed points. Below 14 K either the vapor pressure of helium or a constant-volume gas thermometer<br />

is <strong>to</strong> be used. Above 1235 K radiometry is <strong>to</strong> be used in conjunction with the Planck radiation law,<br />

5 c 2/T 1<br />

L c1 (e 1)<br />

where L is the spectral radiance at wavelength . The first radiation constant, c 1 , is 3.741 83 <br />

16 2<br />

10 W · m and the second radiation constant, c 2 , has a value of 0.014 388 m · K.<br />

TABLE 11.54<br />

Fixed Points in the ITS-90<br />

Fixed points T, K t, C<br />

Triple point of hydrogen 13.8033 259.3467<br />

Boiling point of hydrogen at 33 321.3 Pa 17.035 256.115<br />

Boiling point of hydrogen at 101 292 Pa 20.27 252.88<br />

Triple point of neon 24.5561 248.5939<br />

Triple point of oxygen 54.3584 218.7916<br />

Triple point of argon 83.8058 189.3442<br />

Triple point of mercury 234.3156 38.8344<br />

Triple point of water 273.16 0.01<br />

Melting point of gallium 302.9146 29.7646<br />

Freezing point of indium 429.7458 156.5985<br />

Freezing point of tin 505.078 231.928<br />

Freezing point of zinc 692.677 419.527<br />

Freezing point of aluminum 933.473 660.323<br />

Freezing point of silver 1234.93 961.78<br />

Freezing point of gold 1337.33 1064.18<br />

Freezing point of copper 1357.77 1084.62<br />

Secondary reference points <strong>to</strong> extend the scale (IPTS-68):<br />

Freezing point of platinum 2042 1769<br />

Freezing point of rhodium 2236 1963<br />

Freezing point of iridium 2720 2447<br />

Melting point of tungsten 3660 3387<br />

11.10 THERMOCOUPLES<br />

The thermocouple reference data in Tables 11.55 <strong>to</strong> 11.63 give the thermoelectric voltage in millivolts<br />

with the reference junction at 0C. Note that the temperature for a given entry is obtained by<br />

adding the corresponding temperature in the <strong>to</strong>p row <strong>to</strong> that in the left-hand column, regardless of<br />

whether the latter is positive or negative.

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!