Your Thermapen has a micro-thermocouple located at the very tip of its probe shaft. A thermocouple is a set of two heat-sensitive wires that produce a voltage related to temperature difference. This technology is typically found only in professional-grade thermometers and is what sets your Thermapen apart from other digital “instant read” thermometers.
Because the micro-thermocouple is so small, your Thermapen need only be inserted at least 1/8 of an inch (3 millimeters) to get an accurate reading. Other cooking thermometers may need half an inch or more of immersion.
To take a temperature reading with your Thermapen, penetrate the food you are checking with the probe and place the very tip of the probe where you want to measure. When testing doneness in most foods, the coldest part will be the very center of the thickest portion. With larger foods, you can take quick readings with your Thermapen in several locations to verify that the entire portion is done. If you are chilling a food, the center of the thickest part will be the last to cool.
Different parts of a piece of meat will be at different temperatures during the cooking process. It is not unusual for the internal temperature of a large roast or turkey to vary by as much as twenty or thirty degrees F (10 to 15°C) throughout the meat or bird. Even a steak or a boneless chicken breast will show differences of many degrees as you move the tip of your Thermapen probe from the surface toward the center of the piece, or from end to end.
To get a proper reading with your Splash-Proof Thermapen, insert the probe tip into the thickest part of the meat from the top.* Make an effort to avoid any obvious bone or gristle. Note the temperature. Slowly push past the center and you will see the temperature rise in “real time” at every depth in the piece of meat. Slowly withdraw the probe and you will be able to see the temperature change in the opposite direction. If the meat has already been cooked on both sides, the very center of the thickest part should have the lowest reading. That is the best place to gauge doneness.
As you experiment with your Thermapen and gain confidence, you will learn to quickly check a piece of meat, a roast, or a whole bird in several places and depths to gauge your overall progress during cooking. Lesser quality thermometers such as dial types or slower digitals may not show as much temperature difference. Only a very fast and sensitive thermometer like your Thermapen can show you the exact temperature at its tip. This can be very useful as you try to adjust your cooking methods to achieve a more even cooking process.
* Many experts recommend inserting your thermometer probe from the side of a steak or pattie to ensure that you get the probe tip right in the center, where the temperature will be lowest. You can use a pair of tongs to gently lift the piece of meat off the heat with one hand while you take a Thermapen reading from the side with your other hand.