Children are inquisitive, and teaching them about measurements from an early age can help them grasp more complex concepts like mass. In the metric system, units of measurement are derived from fundamental natural dimensions, such as length or mass.
The kilogram is a standard unit for mass. But how is this value determined?
Units of Mass
The most common unit of mass is the gram (g). The kilogram is another standard measure of matter. It is the base unit of mass in the International System of Units (SI).
The kilogram originally was defined as the mass of a cubic decimeter of water at its melting point, but scientists at the 1875 International Metric Convention created an International Prototype Kilogram that became the basis for the measurement. This small platinum-iridium cylinder is kept with six official copies at the National Institute of Standards and Technology in Maryland, United States.
Other SI derived units of mass include the metric ton (t), pound (lb), and ounce (oz). All use the formula mass = density x volume, where the formula uses the atomic and molecular makeup of an object to determine its mass. Unlike weight, which measures an object’s gravitational force, mass is independent of location. This enables a more global understanding of physical systems and events.
Gravitational Force
The gravitational force is the attractive force between bodies of mass. Its magnitude depends directly upon the masses of the two bodies and inversely upon the distance between their centers. The formula is G (mass of the body) / (mass of the other body). This is the law that governs the interaction of heavenly bodies.
Most modern weighing practice involves making comparisons of the gravitational forces exerted on standard and unknown weights. There is an effect that causes systematic errors in comparing this kind of data, called the gravitational configuration effect. It is caused by the fact that the center of gravity of a weight is above its base and depends on the shape of the weight.
Henry Cavendish was able to measure this effect, and his results were consistent with Newton’s law of gravitation between masses. This law is similar to Coulomb’s law for the electrical forces between charged objects, except with charge in place of mass and a different constant.
Measurement Methods
Mass measurement uses balances and scales to determine an object’s weight. The force exerted by gravity on an object is proportional to its mass, which means a heavier object will have more weight than a lighter one. The primary units of mass are grams, kilograms, and pounds in the metric system and ounces in the imperial system.
The simplest method for mass measurement is using a scale or balance. Be sure to make your measurements in a clean area that is free of dust and other debris that could affect the accuracy of your measurement. Also, make sure to zero the scale or press the tare button before measuring your sample.
Another popular method of mass measurement is with a mass spectrometer. This method can be used to measure the molecular masses of biomolecules in solution, including proteins, lipids, DNA, and other macromolecular assemblies. It is compatible with many different buffers and reagents, and it works in an environment that mimics the intracellular aqueous environment of a molecule, allowing you to observe its native behaviour.
Transducers
The most common instrument for measuring mass is a scale. Scales measure the amount of matter within an object and convert this information to weight using spring shock technology or frequency shift technology.
Differential pressure transducers use piezoelectric materials with interdigital electrodes to electrically generate and detect acoustic waves on the surface of an elastic body, enabling mass measurement down to the femto- or zeptogram range. Validyne offers a wide variety of high-temperature and chemical-resistant transducers for pressure measurement, including 316 SS wetted parts and Inconel wetted parts for corrosive liquid applications.
When an accelerometer is used in a mass measurement application, it must be shielded from all high-g shock input energy, otherwise the sensor and amplifier will both experience a zeroshift, which is a nonlinear response at resonance. One of the best ways to ensure that a device can withstand high-g shock is by performing a sensitivity test on it, with a test block of known mass, and observing its acceleration response.