Table of Contents
Advertisement
7
Preparation of test material and test cell
7.1
Solid materials
The following sections base on the international standards for analysis of the
loss characteristics and permittivity of solid electrical insulation like
ASTM D150-11 or IEC 60250.
7.1.1
Preparation of solid material test cells
The measured dielectric properties can be influenced by the presence of
conductive contaminations or moisture on the test cell or the material sample
surface. Thus, the test cell and its electrodes or contact surfaces must be
cleaned before measurement.
7.1.2
Preparation of
Preparation of solid test material
reparation o solid
The measurement error of the permittivity is not only caused by capacitance
The m
The measure
measurem
measurement error (see 8.1 "Error correction" on page 24), but also by the error
in the so
in the solid test material dimensions and structure. Therefore, the test material
shou
should be accurately cut or modeled and measured so that its dimensional error
wi
will not affect the permittivity value.
In general, the size of the solid material should be large enough to allow its
Size and
Size and
Size and
measurement with the required accuracy. Typically, a capacitance of at least
thickness
thickness
thickness
100 pF should be formed by the sample (size and thickness) and test cell. If the
capacity is lower, the accuracy is limited and noise influences can prevent a
good measurement result, especially if the dielectric has low losses. Therefore,
usually a low sample thickness is used.
NOTICE
Follow the cleaning, warning and safety instructions of the test cell manual.
The used solvents or cleaning agents must previously been checked to
ensure that they do not contain contaminations which can influence the
measurements. Ensure that the used solvent or cleaning agent leads to
correct results of known low permittivity and dielectric losses. Some
cleaning procedure examples can be found in the international standards
like ASTM D150-11 or IEC 60250.
11 or IEC 60250.
DANGER
Death or severe injury caused by fire, poisoning or chemical burn
evere injury c
Ensure the safety c
Ensure the safety conditions for using solvents. Protect the personal and
equipment again
equipment against fire and toxic effects. Read the safety instructions of the
solvent or cl
solvent or cleaning agent before cleaning.
Preparation of test material and test cell
test cell or the material sample
es or contact surfaces must be
afety instructions of
gent
t pr
tain contamination
hat the used solven
ow permittivity and
examples can be
nd in
alysis of the
of t
like
nced by the presence of
ed by the presence of
or the materia
ontact surfaces mu
21
Advertisement
Table of Contents
