Terminology

Terminology

  • Date/Time: Thursday, 9 January 2025, 1:11 am

Standard

  • Reference/Benchmark:

    • Ensures consistency and accuracy in measurements.

Types of Standards

  • Physical Standard:

    • Involves measurement and weight.

  • Procedural Standard:

    • Includes methods, techniques, and procedures.

Key Concepts in Measurement

  • Measurement:

    • Represents quantity value.

  • Accuracy:

    • Refers to the closeness between the test result and the accepted value.

  • Precision:

    • Indicates the closeness between repeated test results or data points.

Average Value Formula

  • Formula:

    • Average = Sum of all observations / Total number of observations

Percent Error Formula

  • Percent Error = (Measured Value - Actual Value) / Actual Value x 100

Accuracy vs. Precision

  • Visual Analogy to Darts:

    • Blue Dart: Precise but not accurate.

    • Red Dart: Both high accuracy and precision.

  • Categories:

    • High Accuracy, Low Accuracy

    • High Precision, Low Precision

Uncertainty

  • Defines the doubt in measurements.

  • Exists due to bias or error attributable to:

    • Instrument Precision

    • Human Error

      • Includes Parallax Error (error due to the object’s position appearing different when viewed from various angles).

    • Environmental Factors

Bias/Error

  • Describes the difference between the expected value and the accepted value.

Tolerance

  • Defines the accepted range within which measurements can vary.

Mean Deviation Formula

  • Formula:

    • Mean Deviation (MD) = Σ|x_i - x| / n

      • where n is the number of observations.

Calibration

  • The process of comparing two measurements.

  • Involves configuring an instrument to produce results for a sample within an acceptable range.

METROLOGY

  • Science of Measurement

  • "Metron" & "Logos"

2 SYSTEM OF MEASUREMENT

  • METRIC SYSTEM (SI)

    • Originate in France (1799)

    • Mostly in Asia

    • Most used

    • Prefixes

  • ENGLISH SYSTEM (IMPERIAL)

    • USA

    • Originate in England (1826)

    • Influenced by Anglo-Saxon & Roman

TYPES OF MEASURING TOOLS

  • NON - PRECISION TOOLS

    • Instrument without graduation and anything to read

  • SEMI - PRECISION TOOLS

    • Instrument with graduation but no accuracy

  • PRECISION TOOLS

    • Instrument with graduation or scale that gives right tolerance

TYPES OF SEMI - PRECISION MEASURING TOOLS

  • Tape measure (medida)

  • Inside caliper

  • Measuring tape

  • Outside caliper

  • Steel Rule

  • Oddleg / Hermaphrodite caliper

  • Try square

  • Divider caliper (Compass)