Definition
A hydrostatic electronic balance is an electronic weighing instrument based on Archimedes' principle that accurately determines the density of solids, volumes, or liquids by measuring the difference in buoyancy between air and liquids. It is usually composed of high-precision electronic balances, weighing stands, immersion vessels, temperature control units and other components, and is widely used in materials science, geological research, jewelry identification, chemical and food industries, providing critical data support for material property analysis.
Principle
The core principle of hydrostatic electronic balances is Archimedes' law of buoyancy. When an object is immersed in a liquid, it is subjected to vertical buoyancy, the size of which is equal to the weight of the object to dispose of the liquid. The buoyancy value (F_b) can be calculated by measuring the mass of an object in air (m_air) and the apparent mass in liquid (m_liquid) by measuring it separately by an electronic balance. Combining the density of the liquid (ρ_liquid) with the acceleration of local gravity (g), the volume (V) and density (ρ_object) of the object can be derived. The basic calculation formula is as follows:
F_b = (m_air - m_liquid) × g
V = (m_air - m_liquid) / ρ_liquid
ρ_object = m_air / V = (m_air × ρ_liquid) / (m_air - m_liquid)
The principle also applies to the reverse measurement process of calibrating the density of a liquid by a solid of known density.
Measurement method
The standard steps for density determination using hydrostatic electronic balances typically include three stages: preparation, measurement, and calculation. First, ensure that the instrument is placed horizontally, preheated stably, and that the immersion liquid (e.g., distilled water, ethanol, etc.) compatible with the sample should be selected. When measuring, the dry sample is weighed in the air and the mass value is recorded. The sample is then completely immersed in the liquid using a hanging basket or filament to avoid bubbles and weighed again. If high-precision measurement is required, the temperature of the liquid should be controlled and its corresponding density value should be recorded. Finally, the obtained data is substituted into the density formula for calculation. For porous or absorbent samples, auxiliary methods such as surface treatment or saturation impregnation are required to reduce errors.
Influencing factors
Measurement accuracy is influenced by various factors. In terms of environmental conditions, temperature fluctuations can cause changes in liquid density and sample volume, and air flow can interfere with weighing stability. Sample characteristics such as surface roughness, porosity, or solubility can affect the accuracy of buoyancy measurements. Operating factors include whether the immersion depth is appropriate, whether the sling wire is completely immersed, and whether the bubbles are thoroughly eliminated. The repeatability, linear errors, and resolution of the instrument itself are also important considerations. In addition, details such as liquid purity, evaporation loss, and static build-up need to be controlled during the experiment.
Application:
Hydrostatic electronic balances have a wide range of uses in industry and scientific research. In materials research, it is used to determine the density and porosity of metals, ceramics, plastics, and composites. In geological and mineral analysis, it can help identify rock composition and mineral type. It is commonly used in the jewelry industry to distinguish natural gemstones from synthetic products or to test the purity of precious metals. The chemical sector is used to monitor the density quality of powder, slurry, or liquid products. In the food industry, the physical properties of raw materials such as grains and fats can be analyzed. This technology provides a relatively convenient solution for non-destructive testing.
Selection
When choosing a hydrostatic electronic balance, it is necessary to consider the measurement requirements and instrument parameters. The weighing range and resolution should match the sample quality and accuracy requirements, and usually higher resolution is required for density measurement. Instrument stability and repeatability have a key impact on the reliability of the results. The rigging device needs to be designed to accommodate the shape and size of the sample and facilitate immersion operation. Whether the temperature sensor and automatic density calculation function are integrated can affect work efficiency. In addition, environmental adaptability, ease of calibration and compliance with relevant international standards (e.g. specifications for density determination in ISO and ASTM are also references when selecting. Users should choose based on actual application scenarios, balancing functionality, cost, and long-term maintenance needs.