This clause specifies how to apply the “Codes for Units of Measurement” published by the “United Nations Centre for Trade Facilitation and Electronic Business” (see https://www.unece.org/cefact/codesfortrade/codes_index.html). This recommendation establishes a single list of code elements to represent units of the International System of Units (SI Units) like units of measure for length, mass (weight), volume and other quantities and in addition covers administration, commerce, transport, science, technology, industry etc. It provides a fixed code that can be used for automated evaluation.

Table 21 contains a small excerpt of the relevant columns in the UNECE recommendation:

Table 21 – Examples from the UNECE Recommendation

Excerpt from Recommendation N°. 20, Annex 1

Common Code

Name

Symbol

C81

radian

rad

C25

milliradian

mrad

MMT

millimetre

mm

HMT

hectometre

hm

KMT

kilometre

km

KMQ

kilogram per cubic metre

kg/m3

FAH

degree Fahrenheit

°F

The mapping of the UNECE common codes to EUInformation.unitId, EUInformation.displayName, and EUInformation.description is available here:

http://www.opcfoundation.org/UA/EngineeringUnits/UNECE/UNECE_to_OPCUA.csv

This mapping has been generated as follows:

Int32 unitId = 0; Int32 c; for (i=0; i<=3;i++) {

c = CommonCode[i]; if (c == 0) break; // end of Common Code unitId = unitId << 8; unitId = unitId | c;}