Gauge blocks are used as a wo rking standard to check the calibration of measurement tools such as micrometers.

      An example of a primary standard is the international prototype kilogram (IPK) which is the master kilogram and the primary mass standard for the International System of Units (SI). The IPK is a one kilogram mass of a platinum-iridium alloy maintained by the International Bureau of Weights and Measures in France.

      Another example is the unit of electrical potential, the volt. Formerly it was defined in terms of standard cell electrochemical batteries, which limited the stability and precision of the definition. Currently the volt is defined in terms of the output of a Josephson junction, which bears a direct relationship to fundamental physical constants.

      In contrast, the reference standard for the meter is no longer defined by a physical object. In 1983, the standard meter was redefined as the distance which light travels in a vacuum during 1/299,792,458 of a second.

      Secondary reference standards

      Secondary reference standards are very close approximations of primary reference standards. For example, major national measuring laboratories such as the US's National Institute of Standards and Technology (NIST) will hold a national standard kilogram, which is periodically calibrated against the IPK.

      Working standards

      Although the SI definition of the «meter» is based on a laboratory procedure combining the speed of light and the duration of a second, a machine shop will have a physical working standard (gauge blocks for example) that is used for checking its measuring instruments. Working standards and certified reference materials used in commerce and industry have a traceable relationship to the secondary and primary standards.

       Ex. 2. Answer the following questions

      1. What is standard?

      2. What types of standard do you know?

      3. What is working standard?

      4. What is the advantage of the elimination of artifacts?

      5. What is IPK?

       Ex. 3. Are these sentences true or false?

      1. Gauge blocks are used as a wo rking standard to check the calibration of measurement tools such as micrometers.

      2. The unit of magnetic potential is the volt.

      3. Today the unit of electrical potential is determined in terms of standard cell electrochemical batteries.

      4. In the science of measurement, a standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of any quantity.

      5. The main standards are primary standards.

      6. There is a five-level hierarchy of physical measurement standards.

      7. Secondary reference standards are values of primary reference standards.

       Ex. 4. Fill t he blanks using the following word words: to calibrate techniques constant, basis, national, types, reference, trend, measurement, replace,

      There is a three … of physical measurement standards The main standards ar e p rimary standards. Primary standards allow realizing units of measurements. Historically, units of measure were defined using unique artifacts which were the legal … of units of measure. A continuing … in metrology is these artifact standards аnd … them with practical units of measure. These units will be connected with fundamental physical … They will be defined using standardized …

      Secondary reference standards are very close approximations of рrimary … standards. For example, major national measuring laboratories such as the US's National Institute of Standards and Technology (NIST) will hold a … standard kilogram, which is рeriodically … against the IPK. The third type of standard, a standard which is periodically calibrated against a secondary standard, is known as a working standard. Working standards are used for the calibration of commercial and industrial … equipment.

       Ex. 5. Match the beginning with the endings based on the text

       Ex. 6. Put the questions to the bold-typed words:

      1. People use secondary standards to define approximate values.

      2. Certified reference materials are used in commerce.

      3. The loss of this artifact didn’t create any problems for us.

      4. Electrical potential is very important for the production of cell batteries.

      5. This working standard is used to calibrate measurement equipment.

       Ex. 7. M ake the summary of the text «What is standard?» using the following plan:

      The definition of a standard;

      Types of standard;

      The definitions of the primary standard;

      The definition of the secondary standard;

      The definition of the working standard;

      The spheres of using these standards.

      LESSON 5

Vocabulary

      to confirm – подтверждать – растау, құптау, дәлелдеу

      assigned value – приписанное значение – белгіленген мән

      to assign a value – присваивать значение – мәнді меншіктеу

      reproducible – воспроизводимый – елестететін, еске түсіретін

      shape – форма – пішін,

---

Скачать книгу