# SI and the American Engineering Systems of Units

In this course, we will consider TWO systems of units:
1. Le Systeme Internationale d'Unites (SI) - uses metric units

2. American Engineering System (AE) - uses English units

 Fundamental Dimension U N I T S SI AE Length meter (m) foot (ft) Mass kilogram (kg) pound-mass (lbm) Moles gram-mole (g-mol) pound-mole (lb-mol) Temperature Kelvin (K) Rankine (oR) Time second (s) second (s)
Roll your mouse over this box to close.
• Homework problem hints and answers
• Get Help from Dr. B in the LT Blog
• 120 day membership

Get it ALL for \$5 US

### Ch 1, Lesson B, Page 4 - SI and the American Engineering Systems of Units

• We will consider two different systems of units in Thermo-CD.
• Our primary system of units will be SI, but we will also work with the
American  Engineering System of Units.
• I will refer to this system of units as the AE system.
• Many American students do not like the AE system, but since the majority of industrial concerns in the US still use this system, it is important for you to have a working knowledge of it.
• The heart of any system of units is the set of units that are used for the fundamental dimensions.
• The table shown here gives this information for both the SI and the AE systems.
• I already mentioned that the subscript “m” in lb sub m means pounds mass.
• The idea of a pound-mole may be new to you.  The good news is that it is fairly easy to deal with.
• Just as 12 grams of pure carbon makes up a gram-mole of carbon, 16 lbm makes up one pound-mole of carbon.  No tricks here.
• You should also note that many people, including me, use the symbols “m-o-l” and “m-o-l-e” when we really mean a gram-mole.  You just need to be aware of this.
• You are probably familiar with the Kelvin scale for temperature, but not the Rankine scale.