Dilatometer

noun

1. An instrument used to measure thermal expansion and dilation in solids and liquids.
2. An instrument for the determination of the changes of volume of a substance or for the measurement of its linear expansion.
3. An instrument for measuring the dilatation or expansion of a substance, especially of a fluid.
4. An instrument used to measure the expansion of solids and liquids when heated, or when subjected to some other physical process