A filled-type temperature instrument refers to a type of temperature sensor or thermometer that contains a fill material inside its sensing element or probe. The fill material typically consists of a liquid, such as mercury or alcohol, or a gas, such as nitrogen or argon, which expands or contracts with changes in temperature. These instruments are commonly used for measuring temperature in various industrial, commercial, and laboratory applications.

Here are some common examples of filled-type temperature instruments:

1. Liquid-in-Glass Thermometers:

   • Liquid-in-glass thermometers consist of a glass tube filled with a liquid, usually mercury or alcohol. As the temperature changes, the liquid expands or contracts, causing it to rise or fall within the calibrated scale on the tube. Liquid-in-glass thermometers are simple, inexpensive, and suitable for measuring temperature ranges from below freezing to moderate temperatures.

2. Expansion Thermometers:

   • Expansion thermometers use the thermal expansion of a liquid or gas to measure temperature. These thermometers typically consist of a bulb filled with a liquid or gas connected to a capillary tube. As the temperature changes, the liquid or gas expands or contracts, causing it to move along the capillary tube and indicate the temperature on a calibrated scale.

3. Gas-filled Thermometers:

   • Gas-filled thermometers use the expansion of a gas, such as nitrogen or argon, to measure temperature. These thermometers contain a gas-filled bulb connected to a pressure gauge or a Bourdon tube mechanism. As the temperature changes, the gas expands or contracts, causing the pressure or volume to change, which is then measured and converted into a temperature reading.

4. Vapor-pressure Thermometers:

   • Vapor-pressure thermometers utilize the vapor pressure of a volatile liquid, such as alcohol or ether, to measure temperature. These thermometers consist of a bulb partially filled with the volatile liquid and connected to a pressure gauge or manometer. As the temperature changes, the vapor pressure of the liquid increases or decreases, causing the pressure to change, which is then measured and converted into a temperature reading.

Filled-type temperature instruments are suitable for various applications where simple, reliable, and cost-effective temperature measurement is required. However, they may have limitations in terms of accuracy, response time, and suitability for high-temperature or harsh environments compared to other types of temperature sensors such as thermocouples, RTDs, or infrared sensors.