About Using Digital Probe
Calibration and Other Issues
All our Digital Probes are rapid
response instruments, but they are not instantaneous. It takes any
temperature probe a certain amount of time to reach the equilibrium
temperature. With our Digital Probes there are two techniques to get an
wait at least 10 seconds, then record the reading... or
digital display until a constant temperature reading is obtained.
Either technique will give good
results, but most people use the 10 second technique since the temperature
will have a tendency to wander up and down some even when it has reached a
true equilibrium. And if you are busy, waiting for a steady reading
can be very tedious.
Anybody who is expected to
produce good temperature data must regularly check their instrument for good
performance. Our Digital Probes are very reliable instruments. They do
not ordinarily "lose" their calibration unless physically damaged
or used for extended periods of time in an industrial or commercial setting.
Sometimes a probe can go bad in a gradual way, so it is impossible to know
if you have good readings without undertaking some effort to determine if
the readings are correct. You can test a digital thermometer for
yourself or send it back to use for a traceable and documented calibration.
First, how to check it for yourself:
Anyone can perform this simple
test. First, get some distilled water and make ice cubes out of half of the
water. Take the cubes out of the freezer and crush them in a blender with
the remaining distilled water. If you do not have a blender, put them
inside an old clean towel and beat them with a hammer. Put the fine chips in
with the distilled water.
Using the tip of the probe as a
stirring rod, stir the mixture as vigorously as you possibly can (without
making too much of a mess). The probe should read
at the extreme within ± 1.2°C (± 2.3°F) of the true freezing point 32.0° F or 0° C. Please note: this
does NOT mean that the probe has this much error in normal use, it is just a
practical range to use with a non-laboratory procedure to check the general
function of the unit.
If the unit falls outside of
these limits (high or low), you have a probe that has a calibration problem
and it is likely only to get worse rather than better. Do not use the probe.
If it is inside these limits, it is undoubtedly OK, so you can proceed with
Low battery power will not
affect the accuracy of any of our instruments. The first sign you may
see is that the display is somewhat weak. If you have a weak display, it is
a good idea to replace the battery immediately. Many digital units will give
you a battery warning before low battery power affects the accuracy of your
The probe will reflect accurate
temperatures in the vicinity of the tip for a radius of about five
centimeters (two inches) if used for probing meats, dairy products and other
high density commodities. In order to get a good reading, therefore, it is
important to penetrate the surface of the product by a depth exceeding the
radius of measurement. Information from scientific studies has shown that
this 5-cm radius is a good rule to follow.
In a refrigerated product in a
storage situation, there is very little likelihood that there are
substantial variations in core temperature of the stored product, so a
single penetration below the 5 cm depth is a good rule to follow for general
if the product has been in transit, changed from one refrigerated regime to
another, or is being handled frequently, a single probe measurement may not
be adequate. Again, scientific experience comes to our assistance. We can
use the "rule of three". Basically, the rule of three is
three specific measurements:
at the surface,
in the exact
middle of the product and about
1/3 of the way into
Three measurements of this type
will serve to answer the question: Is this product relatively uniform in
temperature? If the difference between any of the three measurement is
greater than 1.5° C (3° F), then there is sufficient difference to take
notice and not just be satisfied with a single core temperature reading.
Anything less than this is probably insignificant and may be due to random
When taking the surface
temperature on whole meat, poultry, etc., it is important to apply
substantial pressure so that the surface of the product is compressed in
and slightly around the probe tip. Otherwise, surrounding air
temperatures may bias the reading and create an error.