?Phew, I?ve not gained anything!?: Aren?t you relieved when your bathroom scales show that? Probably ? but actually your bathroom scales don?t measure your bodyweight directly. Instead, the strain cell built into it converts the weight force right into a path. In lots of industrial applications, bending beams and shear beams tend to be 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, they are measuring instruments that determine a mass. As a rule, they gauge the weight force occurring. But unlike, for example, 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 right 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 the deformation then gives information regarding your weight, for example (more precisely about your weight force). And with that, it also answers the question of whether you can still order a dessert or simply 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 mounted on or mounted in the measuring bodies. In the measurement process, they become a mechanical intermediate stage.
Exemplory case of strain gauges: They are glued to the measuring body. If the measuring body deforms, this 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.
As an alternative to these glued foil strain gauges, there are force transducers with welded-in thin-film sensors: a technology that the WIKA Group excels in and with which, in the field of force measurement, it is the only supplier out there. The thin-film technology offers a consistently high quality, a precise 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 using 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 determine the weight of small and medium-sized vessels and so are also frequently used in effect measurement. In agricultural engineering, for instance, such load cells are frequently encountered: for example, 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 also beyond these fields of application, bending beams and shear beams may be used in a wide selection 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. In particular, in applications in the building materials industry, the chemical industry, the food industry and medical technology, bending beams and shear beams tend to be 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 could be calculated from the measured data of this gravimetric level monitoring. Meditative supplies a number of advantages:
Level and the exact mass can be measured as well.
Usage of the tank or vessel is not needed (this eliminates contact with the medium).
The measurement is independent of the material, its properties and the geometry of the container.
The bending beam or shear beam could be easily replaced if necessary.
In level measurement, the load 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 should never affect the measuring result and the permanent function. This applies in temperature-critical applications and where robustness and high durability are required ? for example 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 in demand. When sowing or fertilising, for instance, big money can be saved through the precise distribution of the products. The basis for this, as is always the case with automation, are exact measured values, which is why high-precision shear beams (which may also be insensitive to side loads) are perfectly suited.
Bending beams, shear beams and other load cells: versatile problem solvers
Bending and shear beams are among the most popular load cells. With respect to the field of application, you can find other force transducers which you can use. Our program includes load cells created for ranges between 0.3 kg and 300 t.
Single point load cells. They are used in weighing technology for platform scales with smaller and medium sizes. They are also referred to as ?single points? and so are also suitable for eccentric load introductions.
Compression force load cells. Exactly like heavy-duty load cells, they are tailored to the weighing of medium and large vessels and silos. The force introduction is simply as easy because the installation; furthermore, the look is robust.
Tension/compression force load cells. They are mainly utilized for weighing suspended loads. Measurement is made directly in the force path; in addition, the installation is uncomplicated.
Note
Further information on the product range for force measurement, e.g. our bending beams and shear beams, are available on the WIKA website.
See also our article
Load pins: Definition and application areas