CMS CMS Metrology & Measurement Systems 1 — Questions and Answers
Question 1: What is the definition of 'accuracy' in a manufacturing measurement system?
- The ability to get the same reading every time
- How close a measured value is to the true or accepted reference value (Correct answer)
- The smallest increment a gauge can display
- The range of values a gauge can measure
Correct answer: How close a measured value is to the true or accepted reference value
Accuracy describes how close a measurement result is to the true value, while precision describes repeatability regardless of closeness to truth.
Question 2: Which Measurement System Analysis (MSA) study evaluates the combined variation from both repeatability and reproducibility?
- Attribute agreement analysis
- Gauge R&R study (Correct answer)
- Gage linearity study
- Bias study
Correct answer: Gauge R&R study
A Gauge R&R (Gage Repeatability & Reproducibility) study quantifies variation due to the measurement system itself versus the process, combining equipment and appraiser variation.
Question 3: What does 'traceability' mean in the context of manufacturing metrology?
- Tracking finished products through the supply chain
- Linking measurement results to national or international standards through an unbroken chain of calibrations (Correct answer)
- Recording which operator performed each measurement
- Monitoring gauge wear over time
Correct answer: Linking measurement results to national or international standards through an unbroken chain of calibrations
Metrological traceability means measurement results are linked to a reference standard (e.g., NIST) through a documented, unbroken chain of calibrations with stated uncertainties.
Question 4: A micrometer reads 0.001 inch. What does this value represent?
- Its accuracy
- Its resolution (least count) (Correct answer)
- Its repeatability
- Its calibration interval
Correct answer: Its resolution (least count)
Resolution (least count) is the smallest increment that an instrument can display or resolve, which for this micrometer is 0.001 inch.
Question 5: Which instrument is most appropriate for measuring the roundness (circularity) of a precision machined shaft?
- Vernier caliper
- Coordinate measuring machine (CMM)
- Roundness tester (roundness form analyzer) (Correct answer)
- Surface roughness profilometer
Correct answer: Roundness tester (roundness form analyzer)
A roundness tester rotates the part and measures radial deviations from a perfect circle, directly quantifying circularity error.
Question 6: In metrology, what is 'measurement uncertainty'?
- The probability that a gauge will fail during inspection
- A quantified range within which the true value is estimated to lie with a stated confidence level (Correct answer)
- The difference between two consecutive measurements
- The time required to complete a measurement
Correct answer: A quantified range within which the true value is estimated to lie with a stated confidence level
Measurement uncertainty is a quantified estimate of the dispersion of values that could reasonably be attributed to the measured quantity, expressed with a confidence level.
CMS CMS Metrology & Measurement Systems 1
What is the definition of 'accuracy' in a manufacturing measurement system?