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Unformatted text preview: 06-1 06-1 Error Error is the difference between an ideal (or correct) value and an actual value. • Several different types of error can be measured. • An error type can be expressed in several ways. 06-1 EE 4770 Lecture Transparency. Formatted 8:29, 25 January 1999 from lsli06. 06-1 06-2 06-2 Expression of Error Notation I denotes an ideal value . A denotes an actual value. Absolute error defined |I - A| . Percent error defined 100 |I - A| I for I 6 = 0. Consider a transducer designed to measure process variables in the range I ∈ [ x min , x max ]. Percent-full-scale error defined 100 |I - A| x max for x max 6 = 0. 06-2 EE 4770 Lecture Transparency. Formatted 8:29, 25 January 1999 from lsli06. 06-2 06-3 06-3 Types of Error • Model Error. Error in transducer model, H t . • Repeatability Error. Transducer change from occasion to occasion. • Stability Error. Transducer change during use. • Calibration Error. Difference between two transducers of same kind. 06-3 EE 4770 Lecture Transparency. Formatted 8:29, 25 January 1999 from lsli06. 06-3 06-4 06-4 Model Error Let y = H t ( x ) denote a transducer output, response, and process variable. The accuracy of H t ( x ) depends upon how well the transducer is understood and how complex a transfer function can be tolerated. For example, the following are all for the same transducer: Okay: H t1 ( x ) = R o (1 + ax ). Good: H t2 ( x ) = R o (1 + ax + bx 2 ). Better: H t3 ( x ) = R o (1 + ax + bx 2 + cx 3 )....
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This note was uploaded on 12/11/2011 for the course EE 4770 taught by Professor Staff during the Fall '99 term at LSU.
- Fall '99