How to Measure Volume Without Contact

Volume is the amount of space an object or substance takes up. The standard unit for volume is the cubic meter (m³). Mathematically, volume is found by integrating over the shape in 3D space, but in practice dedicated instruments are used to measure it.

For example, volume is used to measure oddly shaped raw materials, to check the size of food products, and to find an engine cylinder’s capacity. Capacity is simply how much a container can hold and is expressed in cubic meters.

Volume meters range from the traditional Japanese “masu” box to laboratory devices such as flasks, graduated cylinders, pipettes, and burettes. Non-contact methods include acoustic volume meters, which rely on sound pressure, and laser volume meters, which use laser light.

Buoyancy = weight of the displaced fluid

The volume measurement method based on Archimedes' principle uses the physical law that "a body immersed in a fluid experience an upward buoyant force equal in magnitude to the weight of the fluid displaced by that body."
For example, when you get into a bathtub filled with water, the water that overflows is equal to the volume of your body. A common practical approach is to use a graduated cylinder: submerge the object in a liquid, note how much the liquid level rises, and the difference equals the object's volume.

This technique is like the Archimedes displacement method but uses seeds instead of a liquid to measure volume. It is suited for items that cannot be immersed in liquid, such as bread or confectionery. Other comparable techniques include the bead displacement method, which uses small beads as a pseudo-fluid, and the sand displacement method.

Archimedes-based volume measurement is precise but makes the object wet. Using seeds avoids wetting, yet soft items can be compressed and give wrong results. When those methods fall short, a laser volumeter is used. The device scans the object with lasers to measure distances and shape, allowing fast, contact-free volume measurements.

Using Archimedes' method can give precise volumes with minimal equipment. However, because it requires a liquid, the object being measured can become wet, so porous items like sponges cannot be measured and food may raise hygiene concerns. Accurate readings require careful control of conditions (maintaining stable temperature and removing air bubbles).

Laser volumeters can work well. They do not touch the item, so nothing gets wet or damaged. They give quick 2D or 3D readouts and make it easy to quantify volume and shape. The downside is they can only measure what they can see, making large items or complex shapes hard to measure.

Although many volume measurement methods exist, each have limitations described earlier.

The KEYENCE VL Series 3D Scanner CMM addresses those limitations by enabling noncontact volume measurement. The VL Series can perform a full 360° scan of an object in minutes and capture its 3D shape with high accuracy. Volume is then calculated directly from the scanned data.

Because the process is non-contact, complex shapes can be measured reliably.

Contact-based methods can deform samples, making accurate volume measurement impossible for some items. Soft products are particularly challenging to measure precisely. KEYENCE’s VL Series 3D scanner CMM uses high precision optics for non-contact scanning, allowing accurate volume measurement.

Cylinder capacity measurement for engines needs to be very accurate, and conventional methods could be imprecise. The KEYENCE VL Series measures dimensions with high accuracy and calculates cylinder capacity from the scan. It can scan large parts in their entirety in 3D, enabling fast, efficient inspections.