# HPDA temperature conversion card

Here is a picture of a temperature conversion index card I have in my HPDA. The scale on the left is for the normal range of temperatures; the scale on the right is for a much broader range that includes temperatures I often need to convert at work.

I made the card by writing a PostScript file and then converting it to a PDF file using ps2pdf. In writing the PostScript, I reused the hashmarks subroutine that I had written for my ruler card.

You may think the Celsius<=>Fahrenheit conversion so simple that this card is a waste. But it’s much faster to scan the card than to pull out the calculator and do the 9/5 and 32 thing. Especially when you don’t have your calculator with you. (Yes, there’s a calculator on my cell phone, but it’s amazingly inconvenient.)

You may also think the scale on the right is useless. It probably is for you, but I used it twice today when I needed to convert the melting points of a some metal alloys. If you dig into the PS file, you’ll see that the code for the scale on the right is on lines 114-174. Cut these out, and you’ll have the everyday temperature scale by itself. Change first number on line 59 from 3.50 to 4.25, and you’ll move the scale to the center of the card.

A slight alteration of this card would be useful for traveling in another country: the temperature scale on the left and a currency conversion scale on the right would take care of two common issues for Americans abroad. Pounds<=>kilograms and miles<=>kilometers could be on the back side.