?Phew, I?ve not gained anything!?: Aren?t you relieved when your bathroom scales show that? Probably ? but actually your bathrooms scales don?t measure your bodyweight directly. Instead, the strain cell included in it converts the weight force right into a path. In many industrial applications, bending beams and shear beams are often used for such measurements.
Background: How is weight measured?
Whether your bathrooms scales, a finely calibrated laboratory balance or the gravimetric level monitor of a silo: In every cases, these are measuring instruments that determine a mass. As a rule, they measure the weight force occurring. But unlike, for instance, a beam balance or a spring balance, the strain cells used for this determine the weight force indirectly. For this purpose, these force transducers convert the weight force into a path.
The principle: In the strain cell, the weight force deforms a built-in spring or perhaps a bending beam. The intensity of this deformation then gives information about your weight, for instance (more precisely about your bodyweight force). And with that, in addition, it answers the question of whether it is possible to still order a dessert or just start thinking about a diet.
The ?core? of bending beams and shear beams
The different design stages of force transducers in weighing technology: shear beam, bending beam, single-point and S force transducer.
How can you regulate how far the measuring bodies of a bending beam or shear beam load cell deform? At this point special strain gauges or thin-film sensors come into play. These are attached to or mounted in the measuring bodies. In the measurement process, they act as a mechanical intermediate stage.
Exemplory case of strain gauges: They are glued to the measuring body. If the measuring body deforms, that is transferred to the strain gauges. These convert the elastic deformations proportionally into electrical signals. Such changes in resistance could be easily and very accurately measured: with a measurement accuracy of between 0.01 % and 0.05 % Fnom. The calibration is made in grams, kilograms or tons.
Instead of these glued foil strain gauges, you can find force transducers with welded-in thin-film sensors: a technology that the WIKA Group excels in sufficient reason for which, in the field of force measurement, it’s the only supplier available to buy. The thin-film technology supplies a consistently high quality, an exact measurement directly in the force flow, very good temperature characteristics and a higher long-term stability. With bending beams and shear beams, the standardised sensor is welded into the measuring element utilizing a laser, which enables automated series production.
Application fields for bending beams and shear beams
Bending beams and shear beams are employed in weighing technology to look for the weight of small and medium-sized vessels and so are also frequently used in force measurement. In agricultural engineering, for example, such load cells are frequently encountered: for instance, when weighing livestock, dosing animal feedstuff, in gravimetric level monitoring of vessels and silos or for weighing straw or hay bales directly in the baling press.
But additionally beyond these fields of application, bending beams and shear beams can be utilized in a wide variety of other ways: for instance, in traditional weighing machine construction, platform weighing (platform scales), weighing in process and dosing systems, vessel scales, crane scales and truck scales. Specifically, in applications in the building materials industry, the chemical industry, the meals industry and medical technology, bending beams and shear beams are often installed.
Practical example: Level monitoring with bending beam or shear beam load cells
Checking fill levels by measuring the weight of the vessel and contents: The filling height of a vessel or tank can be calculated from the measured data of the gravimetric level monitoring. This measurement method offers a number of advantages:
Level and the exact mass can be measured at the same time.
Usage of the tank or vessel is not required (this eliminates connection with the medium).
The measurement is in addition to the material, its properties and the geometry of the container.
The bending beam or shear beam can be easily replaced if necessary.
In level measurement, the strain cells must function whatever the nature and condition of the media. Liquid or solid, aggressive, conductive or non-conductive, forming foam or dust, steaming, hot or cold, with small or large grain size, whatever the geometry of the vessel and whether the medium in the vessel is evenly or unevenly distributed: Such factors must not affect the measuring result and the permanent function. This also applies in temperature-critical applications and where robustness and high durability are needed ? for instance in the steel industry.
Shear beams and bending beams in the agricultural industry
In another practical example, stainless steel sparkles too: In the agricultural industry bending beams for weighing have become much popular. When sowing or fertilising, for instance, a lot of cash can be saved through the precise distribution of the products. The basis because of this, as is definitely the case with automation, are exact measured values, which explains why high-precision shear beams (which are also insensitive to side loads) are perfectly suited.
Bending beams, shear beams along with other load cells: versatile problem solvers
Bending and shear beams are being among the most commonly used load cells. Based on the field of application, there are other force transducers which you can use. Results includes load cells created for ranges between 0.3 kg and 300 t.
Single point load cells. These are found in weighing technology for platform scales with smaller and medium sizes. Also, they are referred to as ?single points? and are also ideal for eccentric load introductions.
Compression force load cells. Exactly like heavy-duty load cells, they’re tailored to the weighing of medium and large vessels and silos. The force introduction is just as easy as the installation; furthermore, the design is robust.
Tension/compression force load cells. These are mainly used for weighing suspended loads. Measurement is made directly in the force path; furthermore, the installation is uncomplicated.
Note
Further information on the merchandise range for force measurement, e.g. our bending beams and shear beams, can be found on the WIKA website.
See also our article
Load pins: Definition and application areas