The pressure thermometer is one of the earliest mechanical thermometers used in industry. It is based on the thermal expansion of a fluid in a closed system or the change in the saturated vapor pressure of a liquid.

It consists of a bulb, a capillary tube and a Bourdon tube pressure gauge head. These three components form a completely sealed system, filled with a certain working medium inside.

Key Points: It converts temperature signals into pressure signals, and then converts them into pointer displacements through the pressure gauge head.

• Robust structure, resistant to vibration: Pure mechanical structure with no electronic components, making it highly suitable for operation in vibrating environments (such as ships, vehicles, and compressors).
• No external power supply required: Operates based on its own physical principles, is safe and explosion-proof, and is suitable for use in flammable and explosive locations.
• Long-distance measurement possible: The capillary can be made very long (typically up to 20 meters, or even 60 meters), allowing the indicator head to be installed at a distance from the measurement point or in a location that is easy to observe.
• Low cost and simple maintenance: Compared to electronic temperature transmitters, it has a lower cost and is easy for operators to understand and maintain.

• Transportation: water temperature gauges and oil temperature gauges for automobiles, tractors, ships, and construction machinery. This is their most classic and widespread application.
• Refrigeration and air conditioning: temperature control and display for refrigerators, cold storage, and central air conditioning systems.
• Remote monitoring of large equipment: when it is necessary to display the temperatures of multiple measurement points on a single control panel, long capillary pressure-type thermometers are very economical and convenient.
• Flammable and explosive environments: as local indicating instruments in areas with high explosion-proof requirements, such as petroleum and chemical industries.
• Process control with low precision requirements: such as plastic machinery, rubber machinery, and hot presses.

The pressure thermometer is a clever, durable and economical mechanical temperature instrument. With its purely mechanical, explosion-proof, vibration-resistant and remote transmission features, it has firmly established its position in the automotive industry, refrigeration equipment and some harsh industrial environments. Although it cannot compete with modern electronic sensors in terms of accuracy and response speed, its outstanding reliability and convenience in specific scenarios make it a classic tool that will never go out of style in the industrial measurement toolbox.