Information

It thus indicates the average
variation of the resistivity per degree
Kelvin in the temperature range
from t
o
to t, referred to the
resistance value R at t
o.
When experimentally determining
the temperature coefficient as well
as during communication between
supplier and customer two points
must be observed:
1. As already mentioned, the
temperature dependence of the
resistivity in general does not
show a linear, but a curved
form. This applies particularly to
certain resistance alloys and is
the reason why differing
temperature coefficients result
from the calculations, because
they depend on the part of the
curve which corresponds to a
certain ∆ t (see the figure on
page 2).
2. Due to the fact that the
temperature dependent
resistance variation is referred
to the resistance value R
o
when
defining the temperature
coefficient values result for
different values of R
o,
even if
the temperature intervals
chosen are of equal width.
This means that together with
the value of the temperature
coefficient the temperature
interval from °C to °C must
always be quoted. Comparison
of test results is possible only if
the test conditions are the
same.
In some alloys the temperature
coefficient can be controlled by
combining certain alloy components.
It can then achieve negative values
or values around 0 between room
temperature and appr. 100°C.
Dependence of Resistivit
y
in Ω · mm² · m
-1
on Temperature for Various Allo
y
s
1) These values apply to a state of equilibrium.
2) These values apply to a state after rapid cooling; see also B. “Special Characteristics of Nickel-Chromium-Alloys”.
page 3