vakiotilavuuskaasulämpömittarin

A vakiotilavuuskaasulämpömittari, often translated as constant volume gas thermometer, is a scientific instrument used for measuring temperature. It operates on the principle that the pressure of a gas at constant volume is directly proportional to its absolute temperature. This relationship is described by Gay-Lussac's law, also known as the pressure law.

The thermometer consists of a bulb filled with a known amount of gas, typically hydrogen or helium, connected to a manometer. The bulb is immersed in the substance whose temperature is to be measured. As the temperature changes, the gas inside the bulb expands or contracts. To maintain a constant volume, the mercury level in the manometer is adjusted. The pressure difference indicated by the manometer then directly relates to the temperature change.

Calibration is crucial for a constant volume gas thermometer. It is typically calibrated at known fixed points, such as the freezing point and boiling point of water, to establish a temperature scale. While historically important and capable of high accuracy, these thermometers are less common today due to their bulkiness, slow response time, and the need for careful handling of the gas. Modern thermometers, such as thermocouples and resistance thermometers, are generally preferred for most applications due to their convenience and portability. However, the constant volume gas thermometer remains a fundamental tool for understanding thermodynamic principles and for calibrating other temperature measuring devices in metrology.