The best instruments for monitoring the doneness of meat remain the cook’s eye and finger. Measuring internal temperature with a thermometer works well for roasts but not for smaller cuts. (Standard kitchen thermometers register temperature along an inch span of their thick metal shaft, not just at the tip. Dial thermometers also require frequent recalibration to maintain their accuracy.) The simplest way to be sure is to cut into the meat and check its color (the loss of fluid is local and minor).