User Calibration and Usage Notes

Calibration and Other Issues

Equilibration

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 equilibrium temperature:

wait at least 10 seconds, then record the reading…or

watch the 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.

Calibration

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 calibration sequence: 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 within 1.3° C or 2.5° 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 confidence.

Batteries and Accuracy

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 reading.

Measurement Technique prodept.gif (4723 bytes)

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 temperature monitoring.

threerule.gif (6057 bytes) However, 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 the product.

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 variations.

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.