How does the HVAC square capillary thermometer work

The HVAC square capillary thermometer is a temperature measurement device widely used in HVAC systems. Its core structure consists of a square dial, a capillary tube, and a temperature-sensing liquid. It accurately measures temperature by utilizing the volume expansion or contraction of the liquid as it changes temperature. The square dial design is not only aesthetically pleasing but also easy to read, ensuring high readability and durability, especially in industrial and commercial air conditioning systems.

Capillary Tube Principle
The capillary tube is a key component of the thermometer, typically with a diameter between 0.3 and 1 mm. The liquid filling the thermometer (such as alcohol or mercury) expands as temperature rises, moving it up the capillary tube, resulting in a change in the indicated position. The length and diameter of the capillary tube directly affect the measurement range and accuracy. A thinner capillary tube produces a more sensitive liquid column displacement, while a longer capillary tube provides stable readings over a wide temperature range.

Liquid Expansion and Temperature Change
The square capillary thermometer's measurement principle is based on the principle of liquid expansion. When heated, the liquid's volume increases, pushing the liquid column in the capillary tube upward. When the temperature decreases, the liquid contracts, causing the column to fall downward. The expansion coefficient of the liquid is carefully designed to ensure a linear relationship between the displacement of the liquid column and temperature changes. This linear response ensures that the thermometer provides accurate and repeatable measurements in HVAC systems.

Square Dial Design Advantages

Square dials offer more than just aesthetic appeal; they also enhance measurement accuracy and readability. The dial typically features clear graduations, which, combined with the change in the height of the liquid column, allow users to quickly and intuitively read the temperature. The square dial design facilitates installation in air ducts, air conditioning units, or pipe walls, making it particularly suitable for multi-point temperature monitoring in industrial environments.

Response Speed ​​and System Compatibility

The response speed of a capillary thermometer depends primarily on the capillary length, liquid type, and bulb size. By optimizing the capillary layout, square capillary thermometers ensure that heating or cooling of the liquid is quickly reflected on the dial reading, meeting the rapid temperature change monitoring requirements of HVAC systems. Furthermore, these thermometers are highly resistant to high temperatures and corrosion, making them suitable for a variety of environments, including air conditioning systems, refrigeration lines, and HVAC ducts.

Accuracy and Calibration
Precise measurement is essential for stable HVAC system operation. Square capillary thermometers undergo rigorous factory calibration to ensure precise alignment of the liquid column movement with the temperature scale. This calibration process typically uses a standard temperature source for multi-point measurement to correct for nonlinear errors. During maintenance, regular inspections of the liquid column integrity and scale comparisons against a standard temperature ensure long-term stable operation of the thermometer.

Usage Environment and Application Scenarios
HVAC square capillary thermometers are widely used in air conditioning ducts, refrigeration units, heating ducts, and laboratory environments. They offer a compact design, intuitive readings, and high reliability, maintaining accurate measurements in high-humidity, high-temperature, and dusty environments. The fluid selection and capillary design also ensure long-term stable performance under extreme conditions, such as in coolant temperature monitoring or air duct temperature regulation.