Measuring mass is a fundamental process in scientific disciplines such as chemistry and biology. Typically, mass is measured using laboratory equipment like balances, which rely on Earth's gravitational force. The downward force exerted by gravity is counteracted by various mechanisms, depending on the measuring instruments used.

Laboratory balances, essential lab equipment, are indispensable tools in research settings due to their precision in detecting even the slightest deviations in mass. Modern analytical balances often include features like automatic calibration and data recording, making them highly efficient. These advancements allow scientists to conduct experiments with accurate measurements, ultimately advancing scientific knowledge.

In this post, we’ll review the various instruments used to measure mass in the lab.

Balances & Scales

In most laboratory settings, balances are the primary instruments used to determine the mass of an object. A balance compares the mass of an object to that of a known mass. Digital scientific balances and beam balances (like the triple beam balance) are common in labs. Mass is typically measured in metric units such as grams or kilograms, which follow the SI unit system.

At home, scales like digital scales or spring-based bathroom scales are used to determine body weight by calculating mass in relation to gravity. Laboratory balances are far more sensitive, capable of measuring mass down to sub-milligram levels, making them essential for precision work.

• Beam Balances: Commonly used in high school labs and educational settings, beam balances measure mass by comparing two objects. These instruments do not account for variations in gravity across different locations.
• Load Cell Instruments: These advanced instruments utilize strain gauge load cells, which are highly accurate, typically within one part in 2,000. Some use frequency shift technology for even higher accuracy, up to one part in 30,000.
• Force Restoration Instruments: These instruments apply force restoration technology to balance the mass being measured. Modern electronic balances with force rebalance transducers offer exceptional accuracy, reaching one part in 10 million in some cases.

Measurement Transducers

When measuring the mass of an object like liquids or materials that cannot be weighed using a standard balance, transducers come into play. These devices measure the mass properties of a substance by transmitting a signal to a processor, which calculates the mass and displays it on an indicator. Transducers are often used in situations where weighing tanks or measuring non-solid materials is required.

Vibrating Tube Mass Sensors

Vibrating tube mass sensors are highly effective for measuring mass at a microscopic level, particularly in fluids. These sensors determine the buoyant mass of an object using the density of the fluid. They are ideal for measuring small biomaterials such as seeds, cells, and embryos. This method provides a portable and cost-effective solution for labs needing to measure small quantities with high accuracy.

Mass or Weight?

There’s a common misconception that mass and weight are the same. Although related, they are distinct concepts. Mass refers to the amount of matter in an object, while weight is the force exerted on that object by gravity. Mass remains constant regardless of location, while weight can change depending on the gravitational force.

For example, an object’s mass will stay the same whether it is on Earth or the Moon, but its weight will differ due to the different gravitational forces in each location. In scientific settings, it's essential to measure mass when using measuring instruments such as balances and other precise tools, as this provides a more consistent measure of matter.

Steps to Measuring Mass

To ensure precise mass measurements in the lab, follow these steps:

1. Prepare the Balance: Ensure the balance is clean and free of debris. It should be on a level surface, and the sample should be placed in a container, such as a graduated cylinder or beaker, to avoid direct contact with the weighing pan.
2. Tare the Scale: Use the tare function to subtract the container’s mass from the total. This ensures you are measuring only the mass of the sample.
3. Place the Sample: Place the container with the sample on the scale, ensuring that external factors like air drafts, evaporation, or vibrations are minimized. Close any balance doors if available.
4. Read the Measurement: Once the sample is placed and the balance stabilizes, record the mass of the sample. Most modern balances will automatically calculate the mass after taring the container.

Sources of Error When Measuring Mass

Even when using precise instruments, several factors can introduce error when measuring mass. Common sources of error include:

• Air Gusts: Air movement can cause fluctuations in the mass reading, leading to inaccurate measurements.
• Dust and Contaminants: Dust or residue on the balance can alter the weight, especially when measuring small quantities.
• Temperature Changes: Temperature variations can cause materials or components to expand or contract, affecting the mass measurement.
• Magnetic Fields: Magnetic fields can interfere with electronic balances.
• Buoyancy: Items being weighed in a humid or moist environment can experience buoyant forces, impacting the reading.
• Meniscus: Errors caused by incorrectly reading the meniscus when measuring liquids can affect the accuracy of volume measurements.

Minimizing these errors by maintaining a controlled environment and using well-calibrated instruments is key to obtaining reliable mass measurements.

Leasing with Excedr

Looking to equip your lab with mass measurement instruments and other essential laboratory equipment without the heavy upfront costs? Excedr offers flexible leasing options for a wide range of lab equipment, including analytical balances, volumetric flasks, and other measuring devices.

Leasing with Excedr allows your lab to stay up-to-date with the latest technologies while preserving capital for other critical needs. Our leasing programs offer predictable, fixed monthly payments, helping you budget effectively while ensuring your equipment is maintained and serviced regularly. This flexibility means you can easily upgrade or adjust your equipment as your lab’s needs evolve.

Explore our leasing options today and learn how Excedr can help your lab thrive.