HP Calculators with native C-F temperature conversion

[Thomas Klemm]

(02-10-2024 07:07 PM)Dave Britten Wrote:  Seems easier to just remember the 9/5 conversion factor and key in a tiny program to carry it out.

But what if you are an eccentric professor of numerical analysis who wakes up one morning and feels feverish?

(…)

So tossing both thermometers into a sink of lukewarm water, he reads the following pairs of temperatures as the water cools:

\(
\begin{array}{|c|c|c|c|c|c|c|}
\hline
n & 1 & 2 & 3 & 4 & 5 & 6 \\
\hline
C & 40.5 & 38.6 & 37.9 & 36.2 & 35.1 & 34.6 \\
\hline
F & 104.5 & 102 & 100 & 97.5 & 95.5 & 94 \\
\hline
\end{array}
\)

Suppose the professor puts the centigrade thermometer in his mouth and finds he has a temperature of 37°C. Should he be worried?

Insert data:

CLEAR REG

104.5 ENTER 40.5 Σ+
102 ENTER 38.6 Σ+
100 ENTER 37.9 Σ+
97.5 ENTER 36.2 Σ+
95.5 ENTER 35.1 Σ+
94 ENTER 34.6 Σ+

Calculate parameters:

GTO 03 R/S

The parameters \(a\) and \(b\) can now be found in registers 1 and 2:

RCL 1
1.76

RCL 2
33.53

Celsius to Fahrenheit:

37
GTO 01 R/S
98.65

It looks like he is safe.

---

This example is from HP-25 Applications Programs:
CHAPTER 6 STATISTICS
CURVE FITTING—LINEAR REGRESSION

I had to chuckle when I read this:

Quote:This thermometer, however, will not fit comfortably into his mouth. Still, with some ingenuity....

I assume that they had a good time writing these manuals.