slides electrical instrumentation lecture 7 version 2

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  • 1. ET8.017Delft University of Technology El. Instr.Electronic Instrumentation Lecturer: Kofi Makinwa K.A.A.Makinwa@TUDelft.NL 015-27 86466 Room. HB13.270 EWI building Teaching Assistant: Saleh Heidary S.H.Shalmany@TUDelft.NL1 ET8.017Delft University of TechnologyIntroduction El. Instr.Goal of a measurement system:Get the most out of a measurement or sensorin terms of information qualityHow?Filtering (averaging) and shieldingCompensation (e.g. feed-forward)Correction (e.g. auto-zeroing)FeedbackModulation and correlation21

2. Accuracy, precision ET8.017Delft University of Technology(resolution) and stability El. Instr.Precise butNot accurate and Accurate but Accurate andnot accurate not precise not precise preciseffff 0 TimeTime TimeTimeAccurateStable butNot stable andStable and(on the average) not accuratenot accurateaccuratebut not stable 4-23 ET8.017Delft University of TechnologySignal processing techniques El. Instr.Add-on techniques:Built in techniques:filtering compensation prefiltering balancing bridge postfiltering correlationfeedback requires an inversecorrection transducer (actuator) post-processingmodulation (e.g. auto-zeroing, chopping linearization) spinning swapping42 3. ET8.017Delft University of Technology Filtering: general principleEl. Instr. prefilterpostfilter interference measurand sensorprocessoroutreduces additive errorsin a specified frequency bandreduces the effects of thermal noise5 ET8.017Delft University of Technology Pre-filtering El. Instr.Pre-filtering (prior to transduction)Mitigates the effects of:electrically induced signals (capacitive) shieldingmagnetically induced signals (inductive) reducing loop area; shieldingchanges in environmental temperature isolation unwanted optical input optical filtersmechanical disturbances (shocks, vibrations) dampers.....63 4. Electrically-induced ET8.017Delft University of Technologyinterference El. Instr.Cssensor systeminterface system Vn,o Vn,iCgCs

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