16. Measurement Systems Flashcards Preview

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Flashcards in 16. Measurement Systems Deck (19):
1

Bias P.251

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

2

Bias: Linearity P. 252

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

3

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

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)

4

Precision P.253

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.

5

Precision: Repeatibility (measurement range) P.254

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)

6

Precision: Reproducibility (measurement average) P.255

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

7

Discrimination: P.256

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

8

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

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

9

Gage R&R P.257

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

10

Percent agreement. P.257

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

11

GR&R measurement adequacy criteria P.257

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)

12

Components of a measurement system P.258

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

13

Type of measurement systems analysis P. 258

-Variables
-Attributes

14

Variable analysis

1. AIAG method
2. ANOVA method
3. Control Chart method

15

GR&R Report (AIAG) P. 262

- 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

16

Attribute analysis

1. Attribute agreement analysis
2. Attribute gage study - Analytic Method

17

Attribute agreement analysis P. 269

-Each appraiser versus standard
-Between appraisers
-All appraisers versus standard
-Within the appraiser

18

Attribute gage study - Analytic Method

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

19

Causes of measurement error (6M)

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