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Why use noncontact infrared thermometers?
 Noncontact
infrared (IR) thermometers use infrared technology to quickly
and conveniently measure the surface temperature of objects.
They provide fast temperature readings without physically
touching the object. You simply aim, pull the trigger and read
the temperature on the LCD display.
Lightweight, compact, and easy-to-use, IR thermometers can
safely measure hot, hazardous, or hard-to-reach surfaces
without contaminating or damaging the object. Also, infrared
thermometers can provide several readings per second, as
compared to contact methods where each measurement can take
several minutes.
How does IR work?
IR thermometers capture the invisible
infrared energy naturally emitted from all objects. Infrared
radiation is part of the electromagnetic spectrum which
includes radio waves, microwaves, visible light, ultraviolet,
gamma, and X-rays.
About Emissivity
 This infrared "invisible heat" of an object is transferred in
three ways: Reflected, Transmitted, and Emitted. Reflected
energy is not particularly related to the temperature of the
target object, and transmitted heat is related to the both the
internal temperature of the target object and the temperature
of the "transmitted to" object. The only type of energy that
can be used to tell that actual surface temperature of the
object is Emitted energy. When IR thermometers are used to
measure surface temperature they can potentially sense all
three kinds of energy, therefore all thermometers have to be
adjusted to read Emitted energy only. Measuring errors are
often caused by IR energy being reflected by light sources.
Some IR thermometers allow you to change the emissivity in the
unit. The value of emissivity for various materials can be
looked up in published emissivity table. Other units have a
fixed, pre-set emissivity of 0.95, which is the emissivity
value for most organic materials and painted or oxidized
surfaces.
If you are using a thermometer with a fixed
emissivity to measure the surface temperature of a shiny
object you can compensate by covering the surface to be
measured with masking tape or flat black paint. Allow time for
the tape or paint to reach the same temperature as the
material underneath. Measure the temperature of the taped or
painted surface. That is the true temperature.
Accurate Temperature Measurement
When measuring shiny surfaces, such as aluminum and
stainless steel, the reflectivity of the surface will skew the
reading of an IR thermometer unless you accommodate for it.
Either coat surfaces such as griddles or cooking pans with a
non-stick cooking spray before you take your reading, or place
a small piece of masking tape on the metal surface and measure
the taped area. An IR thermometer can go from kitchen to cold
storage (above freezing) and still provide an accurate reading
if given time to acclimate to the new ambient temperature.
It's best to leave the unit where it will be used most often.
Note: If the unit is left in an environment below freezing, it
will temporarily fail to operate properly. Use an IR
thermometer to read internal temperatures of liquids, such as
soups or sauces, simply by stirring the liquid and then
reading the surface temperature. Keep the thermometer away
from steam to avoid condensation on the lens, which will skew
your reading.
Factors That Affect the Accuracy of Readings
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1) Field-of-View
Make sure that the target is larger than the spot size
the unit is measuring. The smaller the target, the
closer you should be to it. When accuracy is critical
make sure that the target is at least twice as large
as the spot size. |
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2) Distance to Spot Ratio
The optical system of an infrared
thermometer collects the infrared energy from a circular
measurement spot and focuses it on the detector. Optical
resolution is defined by the ratio of the distance from
instrument to the object compared to the size of the spot
being measured (D:S ratio).
The larger the ratio number the
better the instrument's resolution, and the smaller the the
spot size that can be measured. The laser sighting included in
some instruments only helps to aim at the measured spot.
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Monitoring
Notes
Receiving
Quality assurance begins at the receiving dock.
When a delivery of fresh or frozen food arrives, use your
Global Sensors IR thermometer to check that the products,
shipping crates, and internal temperature of the delivery
truck are all at the right temperatures.
Storage
Once received, verify that frozen and chilled foods
are stored at or below 40°F (4.4°C) to assure freshness and
quality. In supermarkets where product may be stacked unevenly
or too high in display cases and freezers, check to find warm
spots or uneven cooling. Also, you can quickly and frequently
monitor proper temperatures of all items stored in walk-ins.
Cooking
Exact temperatures become vital to preventing
food-borne illness. To avoid bacteria growth, many foods must
be cooked to a specific temperature. An All QA Products
thermometer instantly confirms that your surface temperatures
are within safe parameters. In order to confirm internal
temperatures, you can use All QA Products thermometer that
feature an internal probe.
Holding and Serving
Food products that are ready to be served
or sold and are located in holding or serving areas must be
kept out of the Temperature Danger Zone which is 40 to 140°F
or 4.4 to 60°C.
- Cold Holding With your IR thermometer, quickly verify
that the temperature of products held in open-top
refrigeration units, such as fresh meat or fish displays,
cold buffets, or preparation units, do not exceed 40°F
(4.4°C), as mandated by the FDA's 2000 Food Code.
- Hot Holding Warm prepared foods that are kept in
steam tables, warming ovens, and other heated serving and
holding areas should be carefully monitored to remain at
140°F (60°C) or above. You can use your IR thermometer to
check the internal temperatures of soups, gravies, and
other liquid foods by agitating them before reading.
- Cooling Improper cooling is the number one cause of
food borne illness. After food has been cooked and served,
use your All QA Products thermometer to confirm that
leftovers are taken down to an appropriate
temperature—from above 140 to below 70°F (60 to 21.1°C)
within two hours, and then down to below 40°F (4.4°C)
within another four hours.
- Reheating The last important temperature-related
checkpoint is reheating. Your IR thermometer can confirm
that foods are being reheated to at least 165°F (73.9°C)
to destroy any bacteria caused by improper cooling or
storage techniques.
You can use your noncontact
thermometer to check more than just the temperature of food.
You can also evaluate the performance of your equipment and
machinery.
- Detect hot spots or leaks by taking sample spot
readings of freezers, walk-in coolers, refrigeration
lines, compressor motors, electrical, and HVAC equipment.
- Safely check the temperature and performance of ovens,
ranges, rotisseries, deep fryers and dishwashers.
- Check clean dishes immediately after washing to ensure
that high enough temperature levels were achieved in the
dishwasher for sanitation purposes.
Other Uses in Gourmet/Specialty Cooking
Many specialty food recipes call for very specific
preparation temperatures. For example, sugar used in meringues
and icings relaxes to the softball stage at 220°F (104°C); at
320°F (160°C) caramel reaches the stage for flavoring and
decorating, and at 350°F (177°C) it darkens. By using an IR
thermometer you can instantly check these temperatures and
avoid the mess of using a contact thermometer.
Experience
notwithstanding, it is often difficult to know when cooking
surfaces have reached the proper temperatures. For example, a
common way to test whether a griddle is "pancake ready" is to
see if a drop of water skittles across its surface. But water
does this at a wide temperature range—roughly between 320° to
440°F (160° to 227°C)—whereas pancakes griddle best between
350° and 370°F (177° and 188°C) and meat, on the other hand,
sears best at about 450°F (232°C). By instantly knowing these
temperatures you can avoid the guesswork and ensure food is
cooked perfectly.
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