Vakiopainekaasulämpömittarissa

Vakiopainekaasulämpömittari is a type of gas thermometer that operates at constant pressure. Unlike a constant-volume thermometer, the volume of the gas inside the thermometer changes to maintain a constant pressure as the temperature fluctuates. This type of thermometer is based on Charles's Law, which states that for a fixed amount of gas at constant pressure, the volume is directly proportional to its absolute temperature.

The construction of a vakiopainekaasulämpömittari typically involves a bulb filled with a gas, such as hydrogen or helium, connected to a mercury reservoir. By adjusting the position of the mercury reservoir, the pressure of the gas can be kept constant. The volume of the gas is then measured, and this volume is used to determine the temperature. Calibration is performed using known fixed points, like the freezing and boiling points of water.

Vakiopainekaasulämpömittarit are known for their accuracy and sensitivity, especially at low temperatures. However, they are also more complex to construct and operate compared to other types of thermometers. The gas used must be inert and have a low coefficient of thermal expansion for optimal performance. Due to their size and the need for constant pressure adjustment, they are not as commonly used for everyday measurements as liquid-in-glass thermometers or thermocouples, but they are valuable in scientific research and calibration laboratories where high precision is required.