## Inspection Training

Class Information
 Tooling U-SME classes are offered at the beginner, intermediate, and advanced levels. The typical class consists of 12 to 25 lessons and will take approximately one hour to complete.
 Class Name: Linear Instrument Characteristics 115 Description: This class describes the various characteristics of linear measuring instruments and explains how variation affects the inspection process. Includes an Interactive Lab. Difficulty: Beginner Number of Lessons: 15 Language: English, Spanish

Class Outline
• Objectives
• The Importance of Measuring Length
• What Is Variation?
• Accuracy
• Error In Measurement
• Precision
• Calibration
• Stability
• Linearity
• Resolution
• Amplification
• Hysteresis
• Factors Affecting Measurement
• Cost of Measurement
• Summary

Class Objectives
• Identify the most common measured quantity.
• Define variation.
• Define accuracy.
• Describe how errors affect the measuring process.
• Define precision.
• Describe how calibration eliminates errors.
• Define stability.
• Define linearity.
• Define resolution.
• Define amplification.
• Define hysteresis.
• Identify the factors that affect measurement.
• Describe how inspection affects costs.

Class Vocabulary

Vocabulary TermDefinition
The difference between a measurement reading and the true value of that measurement.
The movement of a measuring instrument's contact points in relation to the amount of readout on the needle or scale.
The predicted difference on average between the measurement and the true value. Bias is also known as accuracy.
The comparison of a device with unknown accuracy to a device with a known, accurate standard to eliminate any variation in the device being checked.
A measuring instrument with two pairs of jaws on one end and a long beam containing a marked scale of unit divisions. One pair of jaws measures external features; the other pair measures internal features.
A sophisticated measuring instrument with a flat polished table and a suspended probe that measures parts in three-dimensional space.
The amount of deviation in a measurement that is accounted for in the calibration process. You can either add the correction factor to the measured value or adjust the measuring instrument.
A type of measuring instrument that measures the depth of holes, slots, or recesses.
A measuring instrument with a contact point attached to a spindle and gears that moves a pointer on the dial. Dial indicators have graduations that are available for reading different measurement values.
The distance between two lines on a scale or the fineness of an instrument's divisions of measurement units.
The actual change in the measurement value when the same characteristic is measured under the same conditions, same operator, at different points in time. Drift indicates how often a measurement needs recalibration.
The amount of deviation from a standard or specification. Errors should be eliminated in the measuring process.
The actual difference between a measurement value and the known standard value.
A device that determines whether or not a part feature is within specified limits. Most gages do not provide an actual measurement value. However, measuring instruments are also sometimes called gages.
A dense, wear-resistant material that is capable of excellent flatness. Granite is often used for inspection surfaces.
A diagram that represents the variation of one variable compared to another.
A type of measuring instrument with a precision finished base, a beam that is at a right angle to the base, and an indicator.
The delay between the action and reaction of a measuring instrument. Hysteresis is the amount of error that results when this action occurs.
The amount of error change throughout an instrument's measurement range. Linearity is also the amount of deviation from an instrument's ideal straight-line performance.
A device used to inspect, measure, test, or examine parts in order to determine compliance with required specifications.
A U-shaped measuring instrument with a threaded spindle that slowly advances toward a small anvil. Micrometers are available in numerous types for measuring assorted dimensions and features.
A hardened, cylindrical gage used to inspect the size of a hole. Plug gages are available in standardized diameters.
The degree to which an instrument will repeat the same measurement over a period of time.
The ability to obtain consistent results when measuring the same part with the same measuring instrument.
The smallest change in a measured value that the instrument can detect. Resolution is also known as sensitivity.
The inspection guideline stating that a measuring instrument must be ten times more precise than the acceptable tolerance of the inspected part feature.
The angle of a line that appears when comparing two variables on a graph.
The limit of measurement values that an instrument is capable of reading. The dimension being measured must fit inside this range.
The ability of a measuring instrument to retain its calibration over a long period of time. Stability determines an instrument's consistency over time.
A recognized true value. Calibration must compare measurement values to a known standard.
An error that is not determined by chance but is introduced by an inaccuracy in the system. Systematic errors are predictable and expected.
The way a material behaves due to changes in heat. Measuring instruments have thermally stable characteristics so that they are not affected by temperature increases.
The unwanted but acceptable deviation from a desired dimension.
A difference between two or more similar things.