Measures

measures: see weights and measures.

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Measures 

means of measurements used to reproduce physical quantities of some given value. Measures can be quite simple, as, for example, measures of mass (weight) or of holding capacity (measuring cups, cylinders); or they can be more complex, such as standard cells (measures of electromotive force), coils of electric resistances, and photometers. Measures can be classified as single-valued (those reproducing the physical magnitude of a single value) or multivalued (those providing for reproduction of a number of magnitudes of different value, for example, several different lengths). Examples of the first kind are weights, measuring flasks, and inductance coils; those of the second kind are graduated rulers, variable capacitors, and inductance variometers. Measures can be combined into sets, such as sets of weights and sets of end blocks of length. Such sets are used for a step-by-step reproduction of a number of quantities of the same kind within a certain range of values. Sets of measures of electrical quantities are sometimes equipped with switches, and thus form boxes, such as resistance boxes and capacitance boxes.

The rated value of a measure is understood to be the value indicated on the measure or assigned to it, such as a weight of one kilogram or a resistance coil of one ohm. The actual value of a measure is the value that is actually reproduced by the measure, determined so accurately that the error of the measure can be neglected in using the measure. The difference between the rated and actual value of a measure is approximately equal to the error of the measure. A measure should remain stable with passage of time.

Measures are divided into classes of precision, depending on the magnitude of permissible error. Measures are used as standards, as base standards, or as working standards for measurements. The base standards are calibrated against standards and are used in checking the working standards. The error of a measure falls within permissible limits only for certain physical conditions, such as certain values of temperature, pressure, and humidity; these conditions are shown in the instructions for the calibration and use of the measures. Measures often become components of more complex measuring instruments or installations. Standard substances constitute a separate category of measures. Such substances are pure substances or substances prepared in accordance with particular specifications, and these substances have known and reproducible properties. Examples are pure water, pure gases (hydrogen, oxygen), pure metals (zinc, silver, gold, platinum), and benzoic acid. Also classified as measures are the increasingly widely used standard samples having definite physical properties (for example, samples of steel having a definite composition, hardness, or some other parameter).

REFERENCES

Malikov, S. F., and N. I. Tiurin. Vvedenie v metrologiiu, 2nd ed. Moscow, 1966.
Shirokov, K. P. Obshchie voprosy metrologii. Moscow, 1967.
GOST 12656–67: Giri obraztsovye.
GOST 7328–65: Giri obshchego naznacheniia.
GOST 12069–66: Mery dliny shtrikhovye.
GOST 13581–68: Mery dliny kontsevye ploskoparallel’nye iz tverdogo splava.
GOST 1770–64: Mery vmestimosti stekliannye tekhnicheskie.

K. P. SHIROKOV