The accuracy of an instrument depends on 5 basic elements (SWIPE)

  1. S- Standard
  2. W- Workpiece
  3. I- Instrument
  4. P= Person
  5. E- Environment


Factor Affecting accuracy of a measuring System 
Factor Affecting accuracy of a measuring System

1. Standard

Normally the measuring instrument is calibrated with a standard are at regular interval. The
standard may be affected by

  • Coefficient of thermal expansion
  • Stability with time
  • Elastic properties
  • Geometric compatibility
  • Position etc

2. Work piece:
The following factors affect the accuracy

  • Cleanliness surface finish etc.
  • Surface defects
  • Hidden geometry
  • Thermal equalization etc

3. Instrument
The inherent characteristics of the instrument which affect the accuracy are

  • Inadequate amplification
  • Scale error
  • Effect of friction backlash hysteresis etc
  • Deformation while handling heavy w/p
  • Calibration error
  • Repeatability and readability

4. Person
The factors responsible for accuracy are

  • Training skill
  • Sense of precision appreciation
  • Ability to select measuring instrument & standard
  • Attitude towards personal accuracy achievement
  • Planning for measurement technique to have minimum just with consistent in precision.

5. Environment
The environmental factor are:

  • Temperature press humidity
  • Clean surrounding and minimum vibration
  • Adequate illumination
  • Temperature equalization between standard w/p and instrument

Higher accuracy can be achieved if all 5 factors are considered and steps are taken to eliminate them.

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