Data Acquisition and Analysis

HU164_Lecture 5

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RESEARCH METHODS:

• Experimental research– Descriptive– Relational– Difference

All Require Data

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Distance Measuring Methods/devices

• Pacing

• Odometer

• Chaining

• Stadia

• Electronic Distance Measuring (EDM)

• Global Positioning System (GPS)

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The “Best” Method

• Environment• Use of the data• Equipment available• Expertise of individuals

• Personal preference

• Topography

• Client specifications

• Regulations

• Standard practice

The most important factor is the intended use of the data.

The best distance measuring method/device to use is influenced by many factors.

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Load Cell

Force, F

Output, Vo

Output, Vo (V)

Input, Fi (kN)

Slope = 5 V/kN

KInput, F (kN) Output, Vo (V)

Sensitivity, K = 5 V/kN

Block Diagram:

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Resolution

This is defined as the smallest input increment change that gives some small but definite numerical change in the output.

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Data Acquisition System

• A data acquisition system consists of many components that are integrated to:

– Sense physical variables (use of transducers)– Condition the electrical signal to make it

readable by an A/D board

Analogue-to-Digital converter

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DAS Functions

• Convert the signal into a digital format acceptable by a computer

• Process,

• Analyze,

• Store, and

• Display

the acquired data with the help of software

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Typical Block Diagram for DAS

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Transducers

Examples

• Temperature• Pressure• Light• Force• Displacement• Level• Electric signals

Sense physical phenomena and translate it into electric signals.

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Signal ConditioningElectrical signals are conditioned so they can be

used by an analog input board. The following

features may be available:

– Amplification - Isolation– Filtering - Linearization

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Analog to Digital (A/D) Converter

• Input signal

• Sampling rateAnalog Input

4 Samples/cycle

8 Samples/cycle

16 Samples/cycle

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A/D Converter: Resolution

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Data Acquisition Software

• It can be the most critical factor in obtaining reliable, high performance operation.

• Transforms the PC and DAQ hardware into a complete DAQ, analysis, and display system.

• Different alternatives:– Programmable software.– Data acquisition software packages.

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Designing a DAS: Factors to Consider

• Fixed or a mobile application• Type of input/output signal: digital or analog• Frequency of input signal • Resolution, range, and gain• Continuous operation• Compatibility between hardware and software.

Are the drivers available• Overall price.

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References

• Measurement and Data Analysis for Engineering and Science (2nd Edition) by Patrick F. Dunn, CRC Press, 2010

• A Practical Guide to Scientific Data Analysis, David J. Livingstone, Wiley, 2009

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All analysis involves theory

• Because your prior ideas guides your eyes

• Because “pure observations”, neutral and

objective, not guided by your “prejustice”, is

unlikely

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Quantitative inquiry

• Theory guides the development of instruments• If not: theory is still embedded in the instrument

– An analysis of the instruments might reveal the underlying theory

• Knowledge of the instrument’s theory-base is necessary to interpret findings in adequate terms

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Data Analysis

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Qualitative inquiry

• Theory guides

–the foci for the study

–the research questions

–the collection of data

–the analysis of data

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Quiz 1

Answer one question only

• State three steps to critically evaluate information and discuss one of them.

• Differentiate between hypothesis, assumption and theory, providing example for each.

12/11/2012