4
0
12.9 Insulat
ing
Needles
for
Small Diameter Stems
If
the
needles extend beyond the stem
,
they should be insulated from direct sunlight
,
a
s the suns influence
will conduct heat back along the stainless steel needles and
confound or swamp the temperature increase from the measurement heat pulse.
The insulating jacket
taken
from
stripping
the
end
of
the
fig
u
re-
8
charging
cable
is
ideal
and
with
the aid of a small amount of silicon grease slides straight on.
Alternatively, some insulating foam could be used. Finally cover the full
installation with aluminium foil
to
reflec
t
direct
radiation.
The
insulating
conductors
or
foam
will
prevent
heat
transfer from the needles touching the
aluminium foil. For further reference it is recommended that you watch the
small
stems installation
before working with small
stem
installations
for
the
firs
t
time.
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