Measurement Data Analysis Quiz

Metrology (The Science of Measurement)

• Metrology is the science of measurement and calibration.
• This is a key topic for ensuring the accuracy and reliability of measurements.
• It must include the national measurement system.

National Measurement System

• The National Measurement System (NMS) ensures consistent measurements across different industries and sectors.
• Several national physical laboratories (NPL) and related organizations contribute to maintaining and supporting the NMS.

Market Competitiveness

• Proof of adherence to legal requirements.
• Proof of meeting contract specifications.
• Proof of conformance with international standards.
• Measurement standards (NPL/NEL/LGC) are key for market competitiveness.
• Accredited Measurement Laboratories (UKAS).
• Formal Specification Standards.
• Accredited Certification Bodies.
• Industry Standards.

The National Measurement System

• Components of the NMS include; research and development, training, measurement standards, and national standards laboratories (e.g., NPL, NEL, LGC).
• These components work together to calibrate instruments and materials, and ensure adherence to legal and industry requirements.

National Physical Laboratory (NPL)

• The National Physical Laboratory is responsible for several areas of physical measurement, including mass, length, density, force, pressure, colour, gas standards, optical radiation, radio, microwave, and acoustics, and time and frequency.
• NPL maintains the UK's national standards.
• NPL provides traceability for length calibration.

TÜV SÜD National Engineering Laboratory

• Provides standards for flow and density measurement for different materials (e.g. gas, water, oil).
• Works on multiphase mixtures.

Laboratory of the Government Chemist (LGC)

• LGC provides proficiency testing (schemes), chemical and biochemical measurement, and certified reference materials.
• LGC provides standards for gas measurements.

Legal Metrology

• Involved in trade measurements, type approval, equipment testing, mass, length, and volume calibration, and EMC testing.
• This component of the NMS relates to legal requirements for measurements.
• Office for Product Safety and Standards plays a central role in legal metrology, in collaboration with the Department for Business, Energy & Industrial Strategy.

Laboratory Accreditation

• UKAS (United Kingdom Accreditation Service) accredits over 500+ laboratories that provide calibration and testing services.
• This ensures consistency and reliability, using the UKAS logo for identification.

Measurement Traceability

• The traceability of measurements is essential for comparing measurements with national or international standards and ensuring accurate results.
• The traceability chain involves working standards, and transfer standards, that are calibrated.
• Measuring instruments are calibrated with respect to the standards, to measure accurately.
• The National Physical laboratory is part of this chain.

Traceability Chain

• A chain of unbroken traceable measurements.

Accuracy and Cost

• There is a trade-off between accuracy and cost in measurement instruments.
• More accurate instruments typically have higher costs.
• National standards such as NPL (National Physical Laboratory) provide the highest level of accuracy in measurement standards.
• Accuracy is measured against a standard.

Transfer Standards

• Necessary for companies who don't have their own calibration laboratories.
• Ideally 10x more accurate than working standards, which are 10x more accurate than the measuring instruments.
• UKAS-accredited measurement labs provide traceability to national standards with uncertainty statements.
• The Transfer Standards are also part of the traceability chain.

Calibration

• Calibration methods are used to ensure accurate measurement instruments.
• The calibration environment has factors such as, temperature, humidity.
• Electrostatic and electromagnetic fields, Human interaction.
• The calibration process is important to determine accuracy and repeatability in measurement instruments.
• Calibration error should be a maximum of ten percent (1:10) of the measurement tolerance/instrument error.

Calibration - Precision and Accuracy

• Precision refers to the instrument's ability to reproduce readings with a given accuracy
• Accuracy refers to how close the reading is to the true value.
• Both accuracy and precision are important for dependable measurements.
• A calibration, ideally, is traceable to a UKAS accreditation.

Calibration Environment

• Calibration environments are difficult to control and depend on factors including temperature, humidity, pressure, vibration, electrostatic fields, electromagnetic fields, and human interaction.

Calibration - Errors

• Measuring instrument errors are broadly divided into systematic and random errors.
• Identifying potential error sources is crucial. These could include human errors or equipment errors, and environmental errors.

Quantification of Error

• Calibration instruments can show inaccuracies in calibration, which may be used to adjust measurement data.
• Errors can be +20 microns which is quantified.
• Instrument error will be estimated for any deviation from its traceable calibration standard (measurement value).

Cosine Errors

• These occur due to misaligned measurement equipment.
• The error depends on the angle to the measuring device.

Sine Errors

• These arise when flat-surfaces are not mutually perpendicular, when taking measurements.
• This is normally minimal with appropriate design considerations on the measurement devices.

A/B/C/D Coordinate Systems, Datums

• Coordinate systems (X,Y,Z) need to be used correctly; polar coordinates may also be helpful.
• CMM coordinate system needs to be aligned with the object coordinate systems.
• The object coordinate system refers to the coordinate system attached to the component being measured
• Using and choosing the correct coordinate systems avoids issues when taking measurements

Workpiece Datums

• Used within the coordinate system for measurements; these should be defined. Various datum points could exist on the component.

Touch Trigger Probes

• Different types of these probes exist (TP1, TP2, TP6, TP20) to measure various parameters.

Scanning Probes

• Different types of these probes exist (SP25, SP600, SP80) to measure various parameters.

Non-Contact Probes

• Limited by line of sight.
• Some success compared to contact probes in accuracy, due to a reduced interaction (contact) with the workpiece.

Stylus Selection

• Maintain stylus short but rigid to prevent deformation.
• Larger stylus balls are preferred for a wider range.
• Different designs are available for application-specific conditions (star styli, pointer styli, disc styli and cylinder styli)

Probing Strategy

• Number of contact points vary with the geometric feature (e.g. straight lines, planes, circles, spheres, cones, ellipses, cylinders, cubes).

Coordinate Systems - CMM

• Familiar (X, Y, Z), for rectilinear systems.
• Polar (θ, r), may be useful in certain cases.
• Correct identification is crucial for accurate measurements.

Coordinate Measuring Machines (CMMs)

• Different types and configurations exist from manual to computerized systems.
• There are different variations of CMM configurations (like Nikon Metrology, Hexagon Metrology).
• CMMs are now widely supplied with powerful 'user-friendly' software packages.
• Examples are provided (like HC-90, HC-50 CMMs).
• Variations in optical CMMs exist (like Werth GmbH, OGP Inc, Mitutoyo Corp., Hexagon Metrology, Mahr GmbH).
• Multiple-Axis measurement arms (such as FARO-ARM (Platinum) and ROMER 3000i) are available.

General Measurement Strategy for CMMs

• Select features to be measured.
• Define the workpiece datum(s).
• Select the workpiece orientation.
• Select workpiece holding methods.
• Qualify the CMM probe.
• Define probing strategy.
• Program the CMM.
• Analyze and record results.

Workpiece Features

• Measuring the features is dependent on their requirement for measuring performance and function
• Measuring features should ideally be cost effective
• Some methods may not be measurable using a CMM

Coordinate Systems (CMM)

• An important issue is aligning the measuring device coordinate system with the component being measured.

Workpiece Datums (for CMM measurements)

• Datum(s) should be defined, in the correct coordinate system.

The Touch Trigger Probe

• Three main types of probes exist, and each serve different functions for measurement

The Scanning Probe

• Multiple types exist with differing purposes for measurement

Non-contacct Probes

• Uses light instead of physical contact for measurement.
• Has some restrictions compared to contact technologies

Stylus Selection

• Keeping the styluses short and stiff and using reasonably large balls is best practice.

Probing Strategies

• Specific minimum and recommended numbers of probing points may be required, depending on the particular geometric features to be measured (e.g., straight lines, planes, circles, spheres, etc.)

Key CMM Issues

• Issues in coordinate measurement principles, Encoder design, Touch Trigger probes, GD&T principles are important, with Verification & calibration, CMM measurement application, Deployment strategies.

Data Analysis & Errors

• The goal is finding confidence in measurements; single points do not represent the whole picture.
• Data analysis is needed to extract meaningful information from measurements; this involves determining the reliability and consistency of the measurement and identifying trends in data over time.
• The measurement value indicates how well the manufacturing process complies with the specifications.
• The reliability of measurements needs to be considered when making decisions. Trends provide information on how a parameter changes over time.
• Data may be numerically or graphically analyzed, using appropriate statistical methods, or using mathematical concepts such as linear/non-linear regression, or least-squares methods; data trends and deviations in values are helpful for analysis.

Data Frequency Analysis

• The frequency analysis of data looks at how often different data points occur within a range.

Numerical Data Analysis

• Numerical analysis of data commonly involves methods for calculating averages, finding maximum and minimum values, calculating ranges, modes, medians, quartiles, deciles, and percentiles, and calculating variances and standard deviations.
• Calculating the standard deviation from mean measured values is important and frequently used.

Least Squares Methods

• Methods used to calculate best-fit lines through data points.

Identifying Error Sources

• Sources of error (systematic and random errors) can include human errors, environmental variations, and equipment inaccuracies.
• Proper identification of these sources allows for better data interpretation, measurement and process confidence

Quantification of Error

• Calibration standards provide a known measurement value against which the instrument accuracy and any error can be quantified.
• Measurements are adjusted to take these errors in account with an uncertainty value

Cosine Errors

• Errors arising from misalignment of measuring instruments.

Sine Errors

• Errors that arise from surfaces that are not perpendicular to the measuring plane.

A/B/C/D Coordinate Systems, Datums

• When defining the measurement location and direction relative to the object being measured

Air/Bessel points

• Ways of applying accurate supporting points to beams to avoid errors due to sagging

Thermal Expansion

• Materials expand and contract according to temperature.
• Knowing the coefficient of thermal expansion and the operating temperature is essential for accurate measurements.

Abbe's Principle

• Aligning the measuring instrument scale with the workpiece will maximize measurement accuracy.

Parallax Errors

• Errors in measurement can arise from a height difference between two graduated faces of instrumentation

Inclination Errors

• Measuring errors that introduce deviations when the transducers are inclined with respect to the measurement direction.

Metrology – Introduction

• This is the study of measurement

On-line Expectations & House-keeping

• Expecting more than 100 emails per day is unrealistic; use the module noticeboard, lectures, or the email address provided as appropriate for communication requests.
• Module Information is given to the class via various methods.
• Lectures/recording of lectures are available on the provided review panel

Basic Module Details

• Metrology, Subtractive Machining, and Electronics Manufacture are part of a particular module.
• Particular details about assessments and an exam are provided and include the type of questions.

Course Texts

• Modules for Metrology, Subtractive Machining & Electronics Manufacture are supported by relevant textbooks.

Module Learn Pages

• Details and learning material are provided via the Module Learn Pages

Module Relationships

• Provides a diagram for Module Relationships.

Relevant Time Measurement

• Examples of relevant time measurements.

Single Shot Time Equipment

• Diagram showing different parts of the equipment are shown.

Quartz Oscillator Compensation

• The frequency stability of quartz oscillators can be affected by aging, temperature, supply voltage, and power supply mode.
• Methods to compensate for these errors exist including temperature-compensated oscillators and oven-stabilised oscillators.

Time Interval Measurement

• Showing a diagram for the measurement

Resolution

• Measurement equipment accuracy depends on resolution; this aspect should be considered in detail when making measurements.

Errors

• Factors that limit accuracy of counters and timers include system resolution, trigger errors, and time base errors.

Definitions

• Definitions of different parameters for measurement.

Time Zones

• Different time zones explained with a world map showing these regions.

Optical Standards

• How wavelengths of light can be used to derive a unit of length; this would involve measuring the time it takes for a light to travel a given distance, given the speed of light.

The 2019 SI Measurement System

• The fundamental system units are based on constants.
• The metre, kilogram, second, ampere, kelvin, candela, and mole are all defined in terms of fundamental constants.

Length Metrology

• A history of metrology length units over time is given
• Including the metric and imperial systems.

Definition of the Metre

• The initial definition of the metre

End Standards

• Describes how and why specific end standards were used for measuring length.

Line Standards

• Shows how and why line standards were developed as length measuring devices.

Optical Standards

• Explains how light can be measured to accurately measure length.

The Dimensional Metrology Range

• Describes the range of length sizes from nanometres to thousands of metres

Measuring Tools

• Describes possible tools including micrometers and vernier calipers.

Gauge Blocks

• Explains the design and function of gauge blocks.
• How sets of gauge blocks and their precision can be used for calibrating other measuring tools

Gauge/Length Bar Calibration

• Explains how gauge blocks and length bars are calibrated using laser interferometers (showing an example).
• The process in this method relates length measurements to calibrated standards.

References

• A list of references for the study notes.

Out of Roundness

• Explains the concept of out-of-roundness.
• Explains how and why an out-of-roundness measurement is essential for specific applications

Measuring Roundness

• Explains how roundness measurements are made, including different methods like using a V-block and a dial gauge

Analyzing Roundness Results

• Explains how to calculate and analyze the out-of-roundness measurements.

Minimum Zone Reference Circles

• Describes the method of calculating the out-of-roundness from the minimum zone reference circles.

Maximum Inscribed Reference Circle

• Details the method for calculating out-of-roundness using the largest contained circle.

Minimum Circumscribed Reference Circle

• Describes the calculation of out-of-roundness using the smallest circle that contains the trace.

Least Squares Reference Circle

• Explains calculation of out-of-roundness using the least-squares method.

Other Measured Parameters

• Details parameters beyond roundness, including eccentricity and concentricity, and squareness

Surface Texture

• A general introduction to this topic, along with an explanation of why it is important, which includes a description of how different machining processes result in different surface textures.

Quantifying Surface Texture

• Parameters that quantify roughness and waviness are explained and how these are measured practically, along with the types of instruments that perform these measurements.

Amplitude Parameter

• Important parameters that quantify roughness (such as Ra) by calculating the absolute average of the deviations from the mean line

Magnitude Parameter

• Explains the calculation of parameters such as Rp (maximum peak height), Rv (peak to valley) and Rz (maximum peak to valley height).

Machining Processes and Their Textures

• Shows a graph to illustrate relative production time & cost associated with different machining processes.
• Lists the machining processes and their surface texture (Ra) values.

Qualifying Surface Texture

• Ways to properly assess surface texture, and the history of these assessment techniques.

Test your knowledge on the methods and significance of analyzing measurement data. This quiz covers topics such as reliability in measurements, numerical analysis techniques, and the importance of graphical representation. Perfect for students studying measurement systems and data analysis.