BS 7737-1:1995

This standard BS 7737-1:1995 Recommended methods for the determination of the dielectric properties of insulating materials at frequencies above 300 MHz is classified in these ICS categories:

• 29.035.01 Insulating materials in general

This recommendation applies to the procedures for the determination of relative permittivity and dielectric dissipation factor and of quantities related to them, such as loss index, of dielectric materials in the microwave frequency region (i.e. frequencies above about 300 MHz up to optical frequencies).

Unlike the test methods employed at lower frequencies (see IEC Publication 250), the test methods dealt with in this recommendation use test specimen and/or test set-up dimensions larger than or comparable to the wavelength of the electromagnetic field of the test frequency.

In theory, the methods described apply only to test materials having the permeability of absolute vacuum. Good approximation in general is obtained for dia- and paramagnetic materials (so-called non-magnetic materials) whereas with ferro- and ferrimagnetic materials special procedures have to be chosen to separate the dielectric and magnetic properties. These latter methods, however, are beyond the scope of this recommendation.

Note on magnetic properties. – Specimens showing magnetic properties may be tested according to this recommendation if permeability is driven into saturation by a d.c. magnetic bias field of sufficient intensity.

With special precautions and by the use of suitably designed measuring cells, liquids and fusible materials can be measured, as well as solid materials, by the methods described.

The measured values are dependent on physical conditions such as frequency, temperature, moisture content, and in special cases on field strength as well.

All measurements and calculations of this recommendation are based on a sinusoidal waveform of angular frequency ω = 2πf.

Recommends procedures to determine the relative permittivity and electric dissipation factor such as loss index in the microwave frequency region.