Методическая разработка по английскому языку по специальности «Стандартизация, сертификация и метрология»

The ideal standard is independently reproducible without uncertainty. This is what the creators of the «meter» length standard were attempting to do in the 19th century when they defined a meter as one ten-millionth of the distance from the equator to one of the Earth’s poles. Later, it was learned that the Earth’s surface is an unreliable basis for a standard. The Earth is not spherical and it is constantly changing in shape. Careful calibrations allowed tolerances as small as 10 parts per million to be distributed and reproduced in metrology laboratories worldwide, regardless of whether the rest of the metric system was implemented and in spite of the shortfalls of the meter’s original basis. Currently, five independent units of measure are internationally recognized: temperature interval, linear distance, electrical current, frequency and mass. Any measurement can be based on one or more of these measurement units. To supplement these five, two units of angle measurement that are also independent are recognized. For example, Ohm's law is a widely known concept in electrical study. Of the three units of measure involved, only current (ampere) is an independent unit. Voltage and resistance units are dependent on current units, as defined by Ohm's law.

It is believed that each of independent units of measure will be defined in terms of the other four independent units eventually. Length (meter) and time (second) are already connected this way. If an accurate time base is available, then a length standard can be reproduced without a meter bar artifact, using the known constant speed of light. Lesser known is the relationship between the luminance (candela) and current (ampere). The candela is defined in terms of the watt, which in turn is derived from the ampere.

Non-commercial measurement details used to be academic curiosities. The development of standards follows the needs of technology. As a r esult, some units of measure have much more resolution than others. The second is reproducible to 1 part in 10¹⁴. As it became possible to measure time more precisely, solar time, believed to be a constant, proved to be very slightly irregular. This resulted in leap second adjustments to keep UTC (universal time coordinate) synchronized with solar time. The candela standard is difficult to recreate. An incandescent bulb design must be used as a secondary standard, a transfer standard. These special candela standard bulbs recreate the candela when a sp ecific amount of current is applied. Luminance (candela) can only be reproduced to 5 % of reading despite having sensors that have accuracies of +/– 50 parts per million (0.005 %) precision. This is due to the standard not being accurately reproducible.

Temperature (kelvin) is defined by agreed fixed points. These points are defined by the state changes of nearly pure materials, generally as they move from liquid to solid. Between these fixed points, Standard Platinum Resistance Thermometers (SPRTs) are used to interpolate temperature values. This mosaic of approaches produces measurement uncertainty which is not uniform over the entire range of temperature measurement. Temperature measurement is coordinated by the International Practical Temperature Scale, maintained by the BIPM.

Ex. 2. Answer the following questions

1. What was learned later about the Earth’s surface ?

2. How many unites of measure are internationally recognized currently ?

3. What is Standard Platinum Thermometer used for ?

4. What do special candela standard bulbs recreate ?

5. What are any measurements based on?

Ex. 3. Are these sentences true or false ?

1. Non-commercial measurement details were studied by scientists.

2. The candela standard is easy to recreate.

3. Voltage and resistance units are independent on current units.

4. Temperature (kelvin) is defined by non-defined fixed points.

5. Standard Platinum Resistance Thermometers (SPRTs) ar e used to interpolate voltage values.

6. Watt is derived from meter.

7. Ten independent units of measure are internationally recognized, currently.

Ex. 4. Fill the blanks using the following word words:

surface, poles, to define, reason, to attempt, length, to reproduce, metrology object.

Standard is an … oridea that can be used some accepted … Ideal standards can be … without uncertainty. The first ideal standard was … to create in the 19^th century. It was connected with «meter» … standard. In the 19th century meter was … as one ten-millionth of the distance from the equator to one of the Earth’s … It was considered as the first ideal standard. Later it was learned that the Earth’s … an unreliable basis for a standard because the Earth could change its shape. Today there are carried out many calibration investigations w hich are widely used in … for establishing standards.