FACTORS AFFECTING ACCURACY OF A MEASURING SYSTEM

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

 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.