Чтение онлайн

national measuring laboratory – национальная измерительная лаборатория – лтты лшеуіш зертханасы

international prototype kilogram (IPK) – международный прототип кило-грамма – халыаралы килограмм прототипы

to hold – фиксировать – жазып алу, белгілеп ою

speed – скорость – шапшады

speed of light – скорость света – жары жылдамдыы

duration – длительность – заты, зынды

machine shop – механический цех – механикалы цех

measuring instruments – измерительные приборы – лшуіш аспаптар

certified reference material – аттестованный стандартный образец – мате-риалды аттестациядан ткен стандарт лгісі

master standard – основной стандарт – негізгі стандарт

fundamental – основной – негізгі, е бастапы

technique – метод – техника, діс

to disrupt – разрушать, подрывать, искажать – ирату, таландау, бзу

Ex.1 read and translate the text

What is standard?

In the science of measurement, a standard is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. Standards are the fundamental reference for a sy stem of weights and measures, against which all other measuring devices are compared. Historical standards for length, volume, and mass were defined by many different authorities, which resulted in confusion and inaccuracy of measurements. Modern measurements are defined in relationship to internationally- standardized reference objects, which are used under carefully controlled laboratory conditions to define the units of length, mass, electrical potential, and other physical quantities.

There is a three-level hierarchy of physical measurement standards. At the top of the tree are the master standards – these are known as primary standards. Primary standards are made to the highest metrological quality and are the realization of their unit of measure. Historically, units of measure were generally defined with reference to unique artifacts which were the legal basis of units of measure. A continuing trend in metrology is to eliminate as many as possible of the artifact standards and instead define practical units of measure in terms of fundamental physical constants, as demonstrated by standardized technique. One advantage of elimination of artifact standards is that intercomparison of artifacts is no longer required. Another advantage would be that the loss or damage of the artifact standards would not disrupt the system of measures.

The next quality standard in the hierarchy is known as a secondary standard. Secondary standards are calibrated with reference to a primary standard.

The third level 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 measurement equipment.

Primary reference standards

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.