lec03_digi2 - Static Calibration Calibration Defined O as a...

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Slide 1 Static Calibration Calibration Defined O as a fun. of I , linearization, ‘best fitting line’ Range and Span Input/output range, input/output span Nonlinearity Max. nonlinearity in the unit of O : |O actual -O ideal | max Max. nonlinearity as a % of f.s.d: |O actual -O ideal | max /fsd x100% Hysteresis Max. hysteresis in the unit of O : |O inc -O dec | max Max. hysteresis as a % of f.s.d: |O inc -O dec | max /fsd x100% Resolution Smallest input that can be measured Standards
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Slide 2 Standard instrument Standard instrument Standard instrument Standard instrument Environmental Effects In general, output depends on environmental conditions, such as ambient temp., relative humidity, etc. Calibrate at the beginning, middle, and end! Element or system to be calibrated I I M I I O
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Slide 3 Standards Hierarchy Primary Standard Ultimate standard e.g. NIST Interlaboratory Standard Standard against which local standard is checked Local Standard Lab standard e.g. standard pressure gauge Working Instrument e.g. Pressure transducer calibration Increasing accuracy Traceability ladder
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Slide 4 Digital Data Acquisition Data Representation - Digital vs. Analog Analog-to-Digital Conversion Number Systems (Binary Numbers) Sampling & Aliasing
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Slide 5 Data Representation - Digital vs. Analog Digital : 1s and 0s, (1001 1011) 2 Advantages Simplicity of individual units No loss in information during transmission flexibility Disadvantages Slower Loss of resolution Analog : 3.141592687. .., 1/3 Advantages Faster Continuous Cheaper Disadvantages Noise Not flexible
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Slide 6 -1.5 -1 -0.5 0 0.5 1 1.5 0 1 2 3 4 5 6 7 8 Time Voltage Converts analog voltages to binary integers. Analog-to-Digital Conversion ADC Analog Voltage Binary Integers (0s & 1s) Sampling 1/T Sampling frequency T Sampling period Coding Samples
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Slide 7 Analog-to-Digital Conversion ADC calibration How many codes it can generate with n bits? 2 n Calibration Curve ( 3 bit ADC) 0 1 2 3 7 6 5 4 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 Analog Voltage Integer Code 000 001 010 011 100 101 110 111
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Slide 8 Input Range Unipolar: ( 0, V ADCMAX ) Bipolar: ( -V ADCMAX , +V ADCMAX ) (Nominal Range) Clipping : If |V IN | > |V ADCMAX |, then |V OUT | = |V ADCMAX | Analog-to-Digital Conversion time V ADCMAX -V ADCMAX
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Slide 9 Quantization Interval ( Q ) n bit ADC, the input range is divided into 2 n -1 intervals.
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This note was uploaded on 12/26/2011 for the course ME 365 taught by Professor Merkle during the Fall '07 term at Purdue University-West Lafayette.

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lec03_digi2 - Static Calibration Calibration Defined O as a...

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