Definition

Noun: A gas thermometer is a scientific instrument that determines temperature by measuring changes in the pressure of a gas that is confined at a constant volume.

Usage

The term gas thermometer is used specifically in scientific and technical contexts, such as physics, engineering, and metrology, to describe a type of thermometer based on the physical properties of gases.

Examples

• The laboratory used a highly accurate gas thermometer to calibrate other temperature sensors.
• In the experiment, the change in pressure recorded by the gas thermometer indicated a precise rise in temperature.
• The constant-volume gas thermometer is a fundamental instrument for defining temperature scales.

Advanced Usage

• Constant-volume gas thermometer: This is the most common and precise type of gas thermometer, where the volume of the gas is held fixed and temperature is derived from pressure measurements. It is often used as a standard for calibrating other thermometers.
• The principle of the gas thermometer is based on the ideal gas law (PV = nRT), where pressure (P) is directly proportional to temperature (T) when volume (V) is constant.

Variants and Related Words

• Thermometer (noun): A general device for measuring temperature.
• Constant-volume thermometer (noun): Another name for the most common type of gas thermometer.
• Gas thermometry (noun): The field or technique of measuring temperature using gas thermometers.

Synonyms

• Constant-volume thermometer
• Gas expansion thermometer (though this can sometimes refer to a different design where volume changes)

Notes on Meaning

The core meaning of gas thermometer is tied to its operational principle: using a gas (often hydrogen, helium, or nitrogen) as the thermometric substance and relying on the pressure-temperature relationship at constant volume. It is distinct from liquid-in-glass thermometers (like mercury thermometers) or electrical thermometers (like thermocouples).

Noun

1. thermometer that measures temperature by changes in the pressure of a gas kept at constant volume