Density is a fundamental physical property that quantifies the mass of a substance per unit volume. Various units are used to express density, each catering to specific industries, scientific disciplines, or practical applications.

Figure 1. SME-TRD with SRD probe

1. How is density measured with the SRD?

The Rheonics SRD measures viscosity and density by means of a balanced torsional resonator, the finned end of which is immersed in the fluid under test. The sensor displaces fluid as it vibrates, the mass of this displaced fluid reduces the resonant frequency and this reduction of resonant frequency is proportional to the fluid´s density. The increase in apparent mass (denser fluid) decreases the frequency.

The damping increases through viscous dissipation in the fluid, the more viscous the fluid, the higher the damping of the resonator. From the damping and resonant frequency, the density and viscosity may be calculated by means of Rheonics' proprietary algorithms.

Figure 2. Rheonics probe response when immersed in a fluid.

2. What Units are available in Rheonics SRD?

These diverse density units are crucial for ensuring accurate and standardized communication of material properties across different fields. The choice of unit depends on the specific characteristics of the substance being measured and the industry or discipline in which the measurement is applied.

1. g/cc (grams per cubic centimeter):
1. Description: Represents the mass of a substance in grams occupying one cubic centimeter of space.
2. Importance: Commonly used in materials science and engineering for solids and liquids.
2. kg/m³ (kilograms per cubic meter):
1. Description: Denotes the mass of a substance in kilograms within a cubic meter.
2. Importance: Widely used in scientific research, engineering, and industry, particularly for gases and liquids.
3. lb/ft³ (pounds per cubic foot):
1. Description: Expresses the mass in pounds of a substance per cubic foot of volume.
2. Importance: Frequently employed in construction, architecture, and building materials.
4. lbm/g (pound-mass per gram):
1. Description: Represents the mass in pounds of a substance per gram.
2. Importance: Less common but may be used in specific applications requiring this unit.
5. lbs/g (pounds per gram):
1. Description: Indicates the mass in pounds of a substance occupying one gram of space.
2. Importance: Relatively uncommon, but may find use in specialized contexts.
6. ppg (pounds per gallon):
1. Description: Denotes the mass of a substance in pounds per gallon of volume.
2. Importance: Frequently used in industries such as oil and gas for expressing the density of drilling fluids.
7. pptf (pounds per thousand cubic feet):
1. Description: Represents the mass in pounds of a substance per thousand cubic feet.
2. Importance: Commonly used in the natural gas industry for measuring gas density.
8. slug/ft³ (slugs per cubic foot):
1. Description: Denotes the mass in slugs of a substance per cubic foot of volume.
2. Importance: Commonly used in engineering, particularly in the United States, for certain calculations involving mass and acceleration.

3. Why is it important to measure density?

Measuring density in quality control ensures consistent material composition, adherence to standards, and detection of contamination. It is vital for optimizing production processes, minimizing waste, and troubleshooting variations in product quality. Accurate density control contributes to customer satisfaction by delivering reliable and high-quality products.