Dear Dennis...
EN-Genius Network's Dennis Feucht answers your design
queries in his new Circuit Design Clinic!
June, 2008
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EN-Genius Network presents a new, interactive
analog design service to readers! Send us your design questions (with
relevant data; schematics in JPEG or GIF, please) for some free
engineering advice from EN-Genius Network's circuit
consultant, Dennis Feucht, on how you might solve a design problem or
improve circuit performance. Submissions may be edited for clarity or
brevity, and submitters and their email addresses will remain anonymous
(unless otherwise indicated). Please send your questions to Dennis here.
Design Techniques For New Engineers:
Units & Pseudo-Units
by Dennis L Feucht
Physical quantities are represented mathematically by numbers indicating their amount. Depending on whether the quantity is discrete or continuous, integers, rational numbers, or real numbers will be used. Quantities such as the complex frequency, s, require complex numbers. All of these numbers, however, are incomplete in themselves in that they do not adequately represent physical quantities. The additional connection between numbers and the physical world is achieved through the use of units.
A unit is the amount of a quantity that is one of it, the “unity” amount: hence the name for unit. A unit is something that exists in the physical world, not in mathematics as such, and is brought into math as a symbol that is multiplied to the number representing the amount of the quantity. For instance, through physical description, an ampere of current is a certain amount of the familiar quantity, with a standard abbreviation of A. If the amount of current in amperes is a number, n, then n A is a complete mathematical description of the value of the quantity.
...download complete article here (208 KB PDF)
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