# IEEE Std 945-2019 pdf download

IEEE Std 945-2019 pdf download.IEEE Recommended Practice for Preferred Metric Units for Use in Electrical and Electronics Science and Technology.

This recommended practice provides the preferred metric units for use in Electrical and Electronics Science and Technology and supports the application of IEEE/ASTM SI 10.

1.2 Purpose

The purpose of this recommended practice is to aid in the selection of appropriate metric units for quantities that arc of interest to electrical and electronic engineers.

2. Normative references

The following referenced documents are indispensable for the application of this document (i.e., they must be understood and used, so each referenced document is cited in text and its relationship to this document is explained). For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments or corrigenda) applies.

IEEE/ASTM SI IOTNI, American National Standard for Metric Practice)

3. Definitions

For the purposes of this document, the following terms and definitions apply. The IEEE Standards Dictionary Online should be consulted for terms not defined in this clause.

area density: The quantity of mass per area.

coefficient of heat transfer: The density of heat flow rate divided by the temperature difference. density: The quantity of mass per volume.

linear density: The quantity of mass per length.

mass concentration: The quantity of mass of a constituent per volume of the mixture. thermal insulance: The temperature difference divided by density of heat flow rate.

thermal resistance: The temperature difference divided by heat flow rate.

NOTE—Coefficient of heat transfer and thermal insulance are reciprocals of each other.4

4. Multiples and submulti pies of SI units

For SI prefixes, symbols, and multiplication factors, see IEEE/ASTM SI 10.

A common practice is to use multiples and submultiples that are a powers of 1 o, also known as the rule of 1000.

5. Space and time

Table 1 provides preferred space and time SI units.