Kelvin Temperature

What Prompts this Writing of Kelvin Temperature

Lord Kelvin, 1824 to 1907.

I recently wrote a technical paper for publication with the ARRL journal the QEX magazine. In the draft I submitted to the QEX editors I had a number of references to temperatures in degrees Kelvin using the degree symbol, o. When the QEX editors returned to me their draft to review before publication I saw that they had deleted my degree symbols and asked them to “correct” the errors. It was at that time that I learned about the convention of not having degree symbols for kelvins.

So, How do you Show Kelvins?

How are you supposed to use that guy in documentation? What are the accepted conventions? There are a variety of avenues to proceed to answer these questions but first, we need to lay down some groundwork.

Do You Want Your Writings to be Respected?

The obvious answer to this question is an unequivocal YES. So the next question is, why is it that you want what you write to be respected? The obvious answer is that you want people to take you seriously. You have a set of knowledge you own, you have taken the time to share that knowledge, and you want to know that your knowledge is recognized as credible.

On a personal level, you gain respect by first practicing accepted grooming practices. People see you before you open your mouth, so you want to put your best foot forward. Secondly, when you finally do get around to opening your mouth, you want your words understood, so you think ahead, laying any necessary groundwork before speaking your central message.

All of those themes exist in different ways regarding what you write. Where you wanted to practice good grooming techniques in person, you also want your documents to be free of spelling errors, have good grammar, and follow little-known conventions.

An example of a little-known convention is the use of closing quotation marks. Does the close quote follow or precede the sentence end period? But even then the answer is not so simple. The answer to this particular question lies in who your reader is. If the reader is a North American reader, then the close quote goes to one side. If the reader is a UK reader, it goes to the other. But the point is that respect for these little-known nuances shows your reader that you should be taken seriously.

Kelvins in Documentation

Temperature conventions are one of those little-known got’chas of North American grammar. An accepted reference source is the AMA. But the AMA requires a paid subscription. We can also get authoritative answers by NIST. You build a better case for your documentation if you can be carful to follow accepted conventions.

What is a Kelvin, Anyhow?

We all know that zero (0) kelvins is absolute zero. But did you notice the conventions followed in the construction of that sentence? More will be said about that later. For now our task is to define what the heck kelvin is, anyhow.

The physical Measurement Laboratory of NIST tells us that

SI Units – Temperature | NIST

The kelvin (K) is defined by taking the fixed numerical value of the Boltzmann constant k to be 1.380 649 ×10−23 when expressed in the unit J K−1, which is equal to kg m2 s−2 K−1, where the kilogram, meter and second are defined in terms of h, c and ∆νCs. The temperature 0 K is commonly referred to as “absolute zero.” On the widely used Celsius temperature scale, water freezes at 0 °C and boils at about 100 °C. One Celsius degree is an interval of 1 K, and zero degrees Celsius is 273.15 K. An interval of one Celsius degree corresponds to an interval of 1.8 Fahrenheit degrees on the Fahrenheit temperature scale.

The Kelvin unit scale was developed to ease the fabrication of many temperature-dependent equations in science. But often times it is necessary to equate a Kelvin measure to a Celsius measure. Conveniently, the relation exists that one kelvins unit is equal to one degree Celsius. It is therefore natural to think that kelvin temperature reporting should follow the conventions of Celsius.

What Are Some of the Conventions Regarding Spaces?

The 11th edition of the AMA Manual of Style tells us that a full space is called for between temperature values and degree symbols. Also, the repetition of symbols is optional when a hyphen is used. Thus, the AMA gives the example:

  • 34.3-44.5 oC

Notice that there is an embedded space between 44.5 and oC. Also note that there is only one occurrence of units while a duplication would have been permissible.

Another convention explicitly called by the 11th edition of the AMA is use of the degree symbol for kelvin temperature measurement. It explicitly states that the degree symbol is NOT to be used.

Yet even another convention given to us is the usage of text relative to temperature. When referring to the relative nature of two or more temperatures, the accepted convention is to use the word “higher” to express a warmer temperature. Likewise, use the word “lower” to express cooler temperatures.

Important Distinctions from NIST

NIST has some very important observations and operational procedures regarding temperature and kelvins. NIST points out that the kelvin unit is not expressed in degrees like Celsius. It is used by itself to describe temperature.

Kelvin: Introduction | NIST

A change of one kelvin is the same amount of temperature change as one degree Celsius, but the Kelvin scale is “absolute” in the sense that it starts at absolute zero, or what Kelvin and other scientists called “infinite cold.” (0 K = -273.15 degrees C = -459.67 degrees F. Room temperature is about 70 degrees F, 21 degrees C or 294 K.)

Note careful distinctions in the quote above.

  • …change of one kelvin is the same…
  • …but the Kelvin scale is “absolute” in…

Why is kelvin capitalized in one clause and then it appears as an ordinary noun in the other? It is a matter of English grammar. In one clause it is a change but in the other a reference to an object named after Lord Kelvin.

These are probably little-known distinctions that you can usually get away with in your technical writing. However, knowledgeable readers may see oversights and note them but not comment on them. When they see little-known distinctions observed, it tells them that the author has objective credibility.