[Elecraft] Temperature Sensors

[Phil Hystad]

Knowing the formulas for conversion means that you can do them in your head.  The arithmetic is easy.

Actually, the arithmetic is trivial if you allow a slight error in your result.  Formula for going from F degrees to C degrees is:

         C = 5/9  *  (F - 32)

Or, five-ninths of result of subtracting 32 from F degree reading.  But, 5/9th is close to 5/10ths for rough, in the head, calculations and 5/10ths is 1/2 or one-half. 

So, to convert degrees F to degrees C you do the following:  subtract 32 then divide the result by 2. 

Easy to do in your head quickly even while carrying on a QSO with someone in Celsius land.  Example, your outdoor temperature is 85 degrees F (meaning, you don't live in the Seattle area) so you subtract 32 to get 53 and divide by 2 which is 27.5 degrees.  The actual value is 5/9th instead of 1/2 (5/10ths) so the correct C reading of 85 degrees F is: 29.44 (and, not many of us can feel the difference in temp of just 2 degrees).

You can even get used to the idea of adding in a fudge factor due to the error in the calculation that might range from 1 to 3 degrees depending on the range of the F value.  The actual error is close 6 percent (that is, result is ~6 percent too small using this trick) so just remember the 6 percent fudge factor).

For C to F just do the opposite:  double your C temp value and add 32.

73, phil


On Jun 22, 2014, at 7:30 AM, Jim Miller <JimMiller at STL-OnLine.Net> wrote:

> I understand the metric system. I have to convert everything.  My mind has been in OUR system for 70 years and doesn't visualize anything until I convert it. Additional comments withheld . 
> 
> I don't force you to do anything my way so why do you try to force me to do things your way?
> 
> Too old for this xxxx. 
> 73, Jim KG0KP
> 
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Charlie T, K3ICH
> Sent: Sunday, June 22, 2014 6:28 AM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] Temperature Sensors
> 
> Personally, I can't WAIT until we endorse the metric system.  Then we'll only have ten months so we can completely eliminate those nasty January's and February's.
> 
> Chas
> 
> 
> ----- Original Message -----
> From: "Mark via Elecraft" <elecraft at mailman.qth.net>
> To: <elecraft at mailman.qth.net>
> Sent: Saturday, June 21, 2014 11:37 PM
> Subject: Re: [Elecraft] Temperature Sensors
> 
> 
>> Don said:  “Yes, but you have to do a bit of math.”
>> 
>> 
>> 
>> 
>> …or use one of the most useful pieces of software ever written (for an 
>> engineer, anyway), Convert (http://joshmadison.com/).  I used it 
>> throughout my career which required skills in both metric and imperial 
>> systems.  Like Morse Code or learning a new language, it gets easy after 
>> you do it for a while, but usually conversion isn’t really necessary.  All 
>> modern electronic components are spec’d in metric.  Electronic power and 
>> temperatures limits have always been in metric units, even for old tubes, 
>> so it makes sense that Elecraft chose to display Deg. C.
>> 
>> 
>> Keeping a few key temperatures in mind really helps.  Water freezes at 0 
>> deg. C, 20 deg. C is about room temperature, 70 deg. C is uncomfortable to 
>> touch, and water boils at 100 deg. C and will definitely hurt to touch. 
>> Write this down, keep it in front of you.  Get familiar with a few 
>> component spec sheets for some of the components in your radio whose 
>> temperatures are displayed, and you will soon start thinking in “degrees 
>> Celsius”.
>> 
>> 
>> Learn, learn, learn.  It will keep you young!
>> 
>> 
>> 
>> 
>> 
>> Regards,
>> 
>> 
>> Mark
>> ars: KE6BB
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