DETERMINING MEASUREMENT ACCURACY

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	DETERMINING MEASUREMENT ACCURACY
by Hristo Stefanov Start ı Defining the Terms ı A Little Theory ı Sources of Error ı Error Budget ı Error Budget Example ı Offset and Gain Errors ı Sources and PDF SOURCES OF ERROR I will not classify the sources of error, nor will I try to list all of them. I simply want to clarify some potential risks. There is an infinite number of error sources that degrade the performance of a measuring system, so you have to select and consider the most significant. This is not a trivial problem and will need some intuition. Information for primary errors can be obtained from datasheets and reference books. They result from the imperfection of components and methods. Hidden errors come from sources that are not obvious, and most of them appear only at performance test. It is difficult to identify and assess such errors at design time, but it is worth making the same effort. The following is my "top-10" list of hidden sources of error: ı power supply instability ı interference ı self-heating ı thermoelectric effect ı PCB deformation ı moisture absorption in the PCB ı ground plane voltage drops ı parasitic resistance, capacitance, and inductance in the PCB ı contamination ı dielectric absorption PREVIOUS • NEXT Circuit Cellar provides up-to-date information for engineers. Visit www.circuitcellar.com for more information and additional articles. For subscription information, call (860) 875-2199, subscribe@circuitcellar.com or subscribe online. ıCircuit Cellar, the Magazine for Computer Applications. Posted with permission.