Telecurso 2000 - Metrologia - 01 História da Metrologia
Introduction to Metrology
Overview of the Module
- Sofia introduces the new module on metrology, emphasizing its significance in measurements and mechanics.
- Caio, an intern, highlights that metrology is crucial for manufacturing processes and ensuring quality through proper measurement methods.
Importance of Accurate Measurements
- An example is provided about a foreign car needing a piston; if local measurements are incorrect, it could lead to malfunctioning parts.
- The goal of metrology is to ensure that locally manufactured pistons can perfectly fit original specifications from abroad.
Practical Measurement Techniques
Measuring with Body Parts
- Sofia engages participants in measuring objects using their body parts (thumb, palm, feet).
- Participants measure various lengths but find this method impractical and imprecise.
Historical Context of Measurement Standards
- Discussion shifts to how ancient civilizations used body parts as measurement standards (e.g., inch, foot).
- In England during the 15th and 16th centuries, common units included inches and yards; these have modern equivalents in centimeters.
Historical Development of Measurement Systems
Biblical References to Measurements
- The Bible mentions specific measurements related to Noah's Ark construction using the cubit as a standard.
- A cubit equals three palms or approximately 66 cm; variations in human body sizes led to inconsistencies in measurements.
Standardization Efforts by Ancient Civilizations
- The need for standardized measures arose due to variability among individuals' body sizes.
- Ancient Egyptians established a unique standard called the cubit based on fixed stone bars for consistency.
Evolution Towards Natural Units
Transition from Body-Based Measures
- Egyptians recorded equivalent lengths on temple walls for periodic verification against their stone bars.
- French efforts in the 10th century involved creating a linear measure called "toise," which was also subject to wear over time.
Search for Reliable Natural Standards
The Evolution of the Meter
Historical Context of Measurement Units
- The transition from using human body measurements to a standardized unit was necessary, leading to the establishment of a natural unit with decimal submultiples.
- The term "meter" originates from the Greek word "metron," meaning measure. It was defined as one ten-millionth of a quarter of the Earth's meridian.
- Two French astronomers, Delambre and Méchain, measured the distance between Dunkirk and Barcelona to establish this standard meter, which was materialized in a platinum bar.
Redefining the Meter
- As scientific advancements progressed, it became clear that more precise measurements were needed; thus, the original definition of the meter was revised.
- The second definition established that a meter is the distance between two ends of a platinum bar at 0°C under minimal flexion conditions.
Further Refinements
- Issues with earlier standards included imperfections in parallelism and material durability; hence, improvements were made by altering its cross-section and adding iridium for strength.
- The third definition from 1889 specified that a meter is based on specific markings on an international standard bar maintained at 0°C and atmospheric pressure.
Modern Definition Based on Light Speed
- Today’s reference temperature for calibration has shifted to 20°C while maintaining historical references like 0°C for consistency in measurement standards.
- Currently, Brazil's standard for measuring meters is based on light speed: one meter equals the distance light travels in vacuum during 1/299792458 seconds.
Importance of Precision in Measurements
- All definitions aimed to enhance precision; tolerances vary significantly across professions—from centimeters for construction workers to microns for metal mechanics.
- Accurate measurement is crucial for quality control in manufacturing processes; proper calibration of instruments ensures reliability in results.
Summary Review