Which device is specially designed to measure temperatures?

The thermometer is a device specifically designed to measure temperature. It operates based on the principle that materials expand and contract when exposed to changes in temperature, which allows it to provide accurate readings of thermal conditions. Thermometers can come in various forms, such as digital or mercury, each calibrated to measure the thermal energy present in a substance or environment.

Other devices mentioned, such as calipers and micrometers, are precision instruments used for measuring dimensions and distances, not temperature. A ruler is also primarily for measuring length and does not provide temperature readings. Therefore, the thermometer stands out as the appropriate choice for measuring temperature due to its specific function and design.