EXTECH
INSTRUMENTS
6
IR255
‐
en
‐
EU_V1.4
9/14
Locating
Hot
or
Cold
Spots
To
detect
a
hot
or
cold
spot,
aim
the
thermometer
at
a
region
beyond
the
target
and
then
scan
the
entire
region
in
a
slow,
up/down
motion.
Distance
to
Spot
Ratio
(Field
of
View)
The
meter’s
field
of
view
is
12:1
(distance
to
spot
ratio).
For
example,
if
the
meter
is
600mm
from
the
target
(spot),
the
diameter
of
the
target
must
be
at
least
50mm.
Other
distances
are
shown
below
in
the
field
of
view
diagram.
Note
that
measurements
should
normally
be
made
closer
than
1200mm
from
the
target.
The
meter
can
measure
from
further
distances
but
the
measurement
may
be
affected
by
external
sources
of
light.
In
addition,
the
spot
size
may
be
so
large
that
it
encompasses
surface
areas
not
intended
to
be
measured.
It
is
necessary
to
ensure
that
the
size
of
the
target
is
larger
than
the
spot
size.
The
smaller
the
target,
the
closer
the
distance
should
be.
See
the
accompanying
diagram.
Emissivity
Emissivity
represents
the
energy
reflectivity
of
a
material.
Most
organic
materials
and
painted
or
oxidized
surfaces
have
an
emissivity
of
approximately
0.95.
If
possible,
masking
tape
or
flat
black
paint
should
be
applied
to
cover
the
measured
surface.
Wait
a
period
of
time
to
allow
the
tape
or
paint
to
reach
thermal
equilibrium
with
the
surface
of
the
covered
object.
Measure
the
temperature
of
the
surface
covered
with
tape
or
paint
only
after
equilibrium
has
been
achieved.