Measures of Electrical Quantities

Measures of Electrical Quantities 

measures that are used to reproduce electrical quantities of some given value. Some measures of electrical quantities are measuring resistors (resistance coils), inductance coils and mutual inductance coils, measuring capacitors, and measures of electromotive force (standard cells). Some of the measures of electrical quantities are variable (multivalued) measures that make it possible to vary the quantity within some given range (for example, variable capacitors and inductance variometers). Measures of electrical quantities can be combined in sets or in boxes or banks of resistance, capacitance, or inductance.

Based on their metrological purpose, measures of electrical quantities are classified as base standards and working standards. Measures of electrical quantities are usually used in measuring instruments of bridge type or of balance type; such instruments make it possible to measure with an accuracy higher than that of direct-measurement instruments.

Measures of electrical quantities are manufactured with various classes of precision. For resistors, there are seven such classes: 0.0005, 0.001, 0.002, 0.005, 0.01, 0.02, and 0.05 (the numbers indicate the permissible deviation of resistance in a resistor from the rated value of the resistor in percent). Capacitors (capacitance banks) have five classes: 0.05, 0.1, 0.2, 0.5, and 1. Inductance coils have seven classes: 0.01, 0.02, 0.05, 0.1, 0.2, 0.5, and 1. Standard cells must meet limits for permissible annual instability from 0.001 to 0.02 percent.

Measures of electrical quantities are capable of reproducing electrical quantities in the ranges from 10^-5 to 10^-9 ohms, from 10^-8 to 10 henrys, and from 10^-3 to 10⁸ picofarads.

REFERENCES

GOST 6864–69: Katushki elektricheskogo soprotivleniia izmeritel’l’nye.
GOST 13654–68: Katushki induktivnosti i vzaimonoi induktivnosti izmeritel’nye.
GOST 6746–65: Magaziny emkosti izmeritel’nye.

K. P. SHIROKOV