The purpose of this document is to provide you with a quick reference to some commonly used HP 48 commands for dealing with unit objects.

Reference: HP 48G Series User's Guide, Chapter 10.

1.) Adding units to a quantity:

You can attach units to any number you enter on your calculator to create a "Unit Object". This can be done in two ways.

a.) Use the Units Catalog menu: Type the number, then hit the right(green) shift key and hit the units button (the "6" key)

-> UNITS

This brings up a list of dimensions on the menu at the bottom of the screen. The list is 3 screens long, use the NXT key to get from one screen to the next. To select a dimension, press the corresponding key immediately beneath the menu item. This brings up a list of units for that particular dimension.

Simply press the menu key corresponding to that unit to attach that unit to your number. For instance, try entering a unit object, for 8 feet:

8[->][UNITS] [LENG][FT]

Your calculator screen should show 8_ft on level 1 of the stack. You can attach multiple units to a single quantity. To make our unit object 8 ft/sec, simply type:

[->][UNITS][TIME][->][S]

Pressing the right shift again told the calculator, that you wanted feet per second, rather than feet-seconds. Your calculator screen should now show 8_ft/s. To get ft/s², simply repeat the key sequence given above.

b.) Type the units directly: Type the number, then hit the right shift and underscore keys to go to algebraic entry mode. Then type in the name of the unit either by spelling out the appropriate abbreviation, or by selecting the appropriate menu option. Use the arithmetic function keys (*,/,y^{x) to create compound units. To create 8 feet per second squared again using this method, use the following key strokes:}

8[->][_][alpha][alpha][<-][F][<-][T][/][[<-][s][alpha][y ^x][2][ENTER]

If you are not familiar with your calculators alphanumeric entry mode reference you manual. The use of the left key produces lower case letters. Unit abbreviations are case-sensitive (i.e. ft is not the same unit as FT).

2.) Arithmetic with units:

Once you have created unit objects, your calculator will force your calculations to be dimensionally homgenous. When performing addition or subtraction on different units of the same dimension, the result will be left in the units of the quantity on the bottom of the screen. To illustrate this, try adding 3 meters and 2 feet.

3.) Converting between Units

Unit conversions can be performed in four ways.

a.) Use the Units catalog menu. Simply hit the left shift key and the name of the unit you wish to convert to. For instance, to convert your result from part 2 to inches, simply type:

[->][UNITS][LENG][<-][in]

b.) Use arithmetic. Just create a unit object with a value of zero and the appropriate units, and add it to your quantity.

c.) Use the Units Command Menu, which can be brought up by hitting the left shift key

followed by the units key. From this menu, you can select the UBASE option, which converts

to SI base units automatically, or

d.) Use the CONV menu option, which converts the value in level 2 of the stack to the units of whatever object is in level 1 of the stack (BTW, this destroys the value in level 1!).

Try converting 100 ft/s to mph using methods (b) and (d), and to m/s using method (c).