Application Note

2 Fluke Corporation Infrared thermometers: electrical, industrial, and HVAC applications
Because electrical currents
generate heat, temperature
monitoring is an efficient way
to predict potential equipment
failure.
Equipment maintenance
Check moving parts and hous-
ings in motors and gear boxes
for hot spots. Temperature
change can indicate develop-
ing problems in many types
of equipment, from ovens and
boilers to freezers. Routine
temperature audits of generators
and their bearings can prevent
expensive repairs. Scanning
bearing temperatures with an
infrared thermometer allows the
maintenance engineer to detect
hot spots and schedule repairs
or replacements before the
problem leads to an equipment
failure.
Building controls
Monitor HVAC/R components for
quick energy audits and room
balancing in a short time. An
IR thermometer with a 60:1
distance-to-spot ratio makes
elevated vents and returns more
accessible.
For example, if a thermometer
has a 10:1 distance to spot ratio,
one can stand 10 inches away
from the target and measure the
temperature of a one-inch circle.
At 10 feet away from the target,
the measurement spot will be a
one-foot circle.
An IR thermometer can
quickly survey compressor
head temperatures, compres-
sor oil sump temperatures,
evaporator coil and suction line
temperatures, discharge line
temperatures, condenser coil and
liquid line temperatures, and fan
motor temperatures.
Insulation on all surfaces can
be scanned for leakage and
losses. Higher temperatures
are indicated by a shift toward
white. Lower temperatures are
indicated by a shift toward
black.
Process/product
Monitor process lines. Check the
temperature of different products
on production lines. These can
vary from rubber tires to plastic,
from concrete to chocolate bars.
Best practices for
infrared temperature
measurement
To get the best non-contact
measurements, follow these
guidelines:
• Get as close as is safely pos-
sible to your target.
• When measuring at a distance,
understand the size of the
measured target based on the
distance-to-spot ratio.
• If you need to measure a
reflective target often, mask
the reflective surface with flat
black paint or tape for best
results. This also helps ensure
the same spot is measured
every time.
• Consider reflected infrared
radiation. Items that have
shiny, reflective surfaces will
reflect infrared energy from
other objects, including the
sun. This can interfere with
measurement of the target’s
radiated infrared energy
• Experiment with several
angles to get the best mea-
surement. A better angle can
often mitigate reflected energy
from other infrared energy
sources.
• Make emissivity adjustments to
minimize measurement errors.
• Consider using a contact
thermometer or a contact
thermometer probe that plugs
into your infrared thermom-
eter to verify readings you are
unsure of.
The size of the tempera-
ture measurement area (the
“spot”) increases with distance.
Infrared thermometers with a
higher “distance-to-spot ratio”
(D:S) can take accurate measure-
ments at a greater distances.
D:S = 10:1 at focus point
1.5 in
12 in
2.4 in
24 in
4 in
36 in
@
38 mm
300 mm
@
60 mm
600 mm
@
100 mm
900 mm
@
@
@
D
S
Fluke Corporation
PO Box 9090, Everett, WA 98206 U.S.A.
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PO Box 1186, 5602 BD
Eindhoven, The Netherlands
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©2012 Fluke Corporation.
Specifications subject to change without notice.
Printed in U.S.A. 5/2012 4213876A_EN
Modification of this document is not permitted
without written permission from Fluke Corporation.
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