This is used to overcome problems due to the variety of ways in which an author may express a particular value.
For example, to find all the references to power stations generating between 20 and 30 MW, values in this range may be expressed as 29.2 MW, 27500 kW, 25 megawatts, 29 MWatt etc., which makes it impossible to retrieve all records matching the search criteria.
Inspec’s numerical data indexing standardises the format, for example, the power of 25 megawatts would be given as 2.5E+07W and a range of 30 Hz to 18 kHz would be given as 3.0E+01 to 1.8+04 Hz.
Values are given in floating point format, e.g. 1.8E+04 for 18000 and 9.5E-01 for 0.95.
Each numerical index term has the following format:
Quantity value (to value) unit where:
Quantity represents the physical quantity e.g. temperature or wavelength
Unit is of the SI type, e.g. metre (m), hertz (Hz), kelvin (K)
Value is the actual value or range expressed in floating point format.
The quantity and unit are given in the numerical data indexing thesaurus. For further information, see the documentation section.