Vakiotilavuuskaasulämpömittari

Vakiotilavuuskaasulämpömittari, often referred to as a constant volume gas thermometer, is a device used to measure temperature based on the pressure changes of a gas kept at a constant volume. The fundamental principle behind its operation is Gay-Lussac's Law, which states that for a fixed amount of gas at constant volume, the pressure is directly proportional to its absolute temperature. Therefore, by measuring the pressure of the gas, one can determine its temperature.

The thermometer typically consists of a sealed container, usually a bulb, filled with a specific amount of gas, such as air, nitrogen, or helium. This container is connected to a pressure measuring device, like a manometer. The gas in the bulb is then exposed to the temperature to be measured. As the temperature changes, the gas inside the bulb expands or contracts. However, in a constant volume gas thermometer, the volume is kept constant by adjusting a mercury reservoir in the manometer. The change in the mercury level indicates the change in pressure.

A calibration process is necessary to establish a temperature scale. This is usually done by exposing the thermometer to known temperatures, such as the melting point of ice (0 degrees Celsius or 273.15 Kelvin) and the boiling point of water (100 degrees Celsius or 373.15 Kelvin), and recording the corresponding pressures. Between these calibration points, the temperature can be calculated using the measured pressure and the established relationship. Constant volume gas thermometers are known for their high accuracy and are often used as primary thermometers for calibrating other temperature measuring devices, especially at very low or very high temperatures where other thermometers might be less reliable.