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1. Lecture # 08 Measurement Standards

2. Measurement Standards 2  Measurement Standards are classified in four level :-  International standards.  Primary standards.  Secondary standards.  Working standards.

3. International standards. 3 Are defined by international agreement , and are maintained at the International Bureau of Weight and Measure in France. These are as accurate as it is scientifically possible to achieve. They may be used for comparison with primary standard, but otherwise unavailable for any application.

4. Primary Standard 4 Are maintained at institutions in various countries around the world, such as the National Bureau of Standards in Washington. These are as accurate as it is scientifically possible to achieve. They are also constructed for the greatest possible accuracy , and their main function is checking the accuracy of secondry standard.

5. Secondary standard 5 Are periodically checked at the institutions the maintain primary standards. Are employed in industry as reference for calibrating high accuracy equipment and component and for verify the accuracy of working standards.

6. Working Standard 6  The working standards are the principal tools of a measurement laboratory.They are used to checked and calibrated general laboratory instrument for accuracy and performance or to perform comparison measurement industrial application.

7. Summary 7 Secondary standards are more accurate than working standard and are used throughout industry for checking working standards and for calibrating high accuracy equipment. Primary standards are more accurate than secondary standards.They are maintained to the highest possible accuracy by national institutions as references for calibrating secondary standards. International Standards are maintained by international agreement and may be used for checking primary standards.

8. Assignment 8  A voltmeter, having a sensitivity of 1,000  /V, reads 100 V on its 150 V scale when connected across an unknown resistor in series with a milliammeter. When the milliammeter reads 5 mA, calculate  a) apparent resistance of the unknown resistor,

9.  b) actual resistance of the unknown resistor 9  c) error due to the loading effect of the voltmeter.