16. Measurement Systems Flashcards

1
Q

Bias P.251

A

Systematic difference between the mean of the measurement results and a reference or true value. AKA accuracy.

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2
Q

Bias: Linearity P. 252

A

The difference in bias through the expected operating range of measurements. (over operating range)

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3
Q

Bias: Stability (of a measurement system) P. 252

A

Change in bias of a measurement system over time and usage when that system is used to measure a master part or standard. (over time)

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4
Q

Precision P.253

A

The closeness of agreement between randomly selected individual measurement results or test results.

Precision depends only on the distribution of random errors, not reference or true value.

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5
Q

Precision: Repeatibility (measurement range) P.254

A

Independent measurement results are obtained with the same method on identical measurement item with same operator/ equipment within a shot period of time. (Equipment variation or within-system variation)

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6
Q

Precision: Reproducibility (measurement average) P.255

A

Independent measurement results are obtained with the same method on identical measurement item with different operators/ equipment. (Appraiser variation)

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7
Q

Discrimination: P.256

A

Measurement system’s capability to detect and indicate small changes in the characteristic measured.

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8
Q

Precision-to-tolerance ratio (PTR) P.256

A

Measure of the capability of the measurement system. ( Less 0.10= Good, >0.30 require improvement)

PTR= 6σ(ms) / USL - LSL

σ(ms) is the estimated SD of the total measurement system variability.

(ms) measurement system

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9
Q

Gage R&R P.257

A

Measurement system analysis done to evaluate the performance of a test method or measurement system.

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10
Q

Percent agreement. P.257

A

Percentage of time in an attribute GR&R study that appraiser agree with 1. themselves 2.other appraisers, 3, known standard.

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11
Q

GR&R measurement adequacy criteria P.257

A
  1. Total percent GR&R in the percent study variation ( Less 10% = Good, 10-30%= Marginal, >30%= inadequate)
  2. Percent tolerance ( Less 10% = Good, 10-30%= Marginal, >30%= inadequate)
  3. Percent contribution ( Less 1%= Acceptable, 1-9%, Marginal, >9%- inadequate)
  4. Number of distinct categories. Min. of 5 level (discrimination)
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12
Q

Components of a measurement system P.258

A
  1. Measurement instrument
  2. Appraisers (Operators)
  3. Methods or procedures for conducting the measurement
  4. Environment
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13
Q

Type of measurement systems analysis P. 258

A
  • Variables

- Attributes

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14
Q

Variable analysis

A
  1. AIAG method
  2. ANOVA method
  3. Control Chart method
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15
Q

GR&R Report (AIAG) P. 262

A
  • Equipment Variation (EV), standard deviation of the variation due to repeatability
  • Appraiser variation (AV), standard deviation of the variation due to reproducibility.
  • GR&R, estimated of the standard deviation of the variation due to measurement system.
  • Part-to-Part variation (PV), standard deviation of the variation due to part differences.
  • Total variation (TV), estimated of the standard deviation of the total variation
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16
Q

Attribute analysis

A
  1. Attribute agreement analysis

2. Attribute gage study - Analytic Method

17
Q

Attribute agreement analysis P. 269

A
  • Each appraiser versus standard
  • Between appraisers
  • All appraisers versus standard
  • Within the appraiser
18
Q

Attribute gage study - Analytic Method

A

Used to determine the amount of bias and repeatability of a measurement system when the response is an attribute variable.

19
Q

Causes of measurement error (6M)

A
  1. Machine
  2. Methods
  3. Man or woman (appraiser)
  4. Mother Nature
  5. Materials (parts)
  6. Measurement
    (7) Management