High precision load cells | OMEGA Waagen GmbH
To determine the mass, load cells based on strain gauges, also known as strain gauge load cells, are the right choice for a wide variety of applications in weighing technology. In our extensive delivery program you will find the following cells with nominal loads from 3 kg to 100 t:
SinglePoint load cells (platform)
Bending beam load cells
Shear beam load cells
Double shear beam load cells
Pressure load cells
S-shaped load cells (tensile force)
Years of expertise in weighing technology, special expertise and friendly customer service characterize us at OMEGA scales. In our online shop you will find a wide range of high-precision load cells as well as suitable mounting modules and accessories for every application. Your desired product is not included? Feel free to contact us! We would be happy to manufacture a special solution for you.
The load cell as the core of every scale
In addition to the evaluation electronics and the construction of the scale, the load cell is one of the core elements of every scale. Depending on the application, different types of load cells are used. In principle, however, the strain gauges are attached to a spring body for all types. When loads are applied, this spring body bends and the strain gauges are compressed or stretched. This changes the input signal. This change is output as a signal. Using evaluation electronics, the weight or the force can be displayed depending on the respective application.
The variety of applications is covered by the different designs of the load cells:
Platform scales mainly use single point load cells, also called platform load cells. These can display very small nominal loads with a correspondingly high resolution and are compensated for corner loads.
In the construction of floor scales, pallet scales and scales with a similar structure, shear beam load cells are mainly used. These can represent higher nominal loads, usually up to 10 t per load cell.
Bending beam load cells are very often used in plant engineering and mechanical engineering and are ideal for applications with dynamic loads.
Double shear bar load cells have very high nominal loads of up to 40 t and are suitable for vehicle scales as well as platform scales which have to withstand high loads.
100 t or more can be represented with pressure load load cells, which means that they are used in axle load scales, vehicle scales and also in silo scales.
S-shaped load cells are particularly suitable for crane scales and all applications in which a tensile force is to be determined. A pressure load is also possible with these load cells, which means that - due to their small installation dimensions - they can also be used for container scales and in plant and mechanical engineering.
Construction of a strain gauge load cell
A load cell essentially consists of a spring body and strain gauges (DMS), which are attached to the spring body. The number and arrangement of the strain gauges depends on the application, from which the various types can also be derived. If a load acts on the load cell, the spring body deforms according to the mass applied. This bending causes the strain gages to expand or contract. This changes the resistance. The resistance decreases with a compression and with an expansion. The difference between the input and output signals is measured by means of an electrical signal, which is fed into the load cell and thus into the strain gauge, and is output into a readable weight value via evaluation electronics.
The strain gauge - strain gauge
Even with slight deformations of the spring body, the electrical resistance of the strain gauges changes. A film is often used as the material on which a measuring grid is applied. This measuring grid consists of metal or semiconductors. Several strain gauges on a carrier (in the case of load cells this is the spring body) arranged in the appropriate geometry are referred to as rosette strain gauges or strain gauges. The shape of the measuring strips is different and is based on the respective application. Metallic strain gauges are based on changes in resistance due to changes in length and cross-section.
Nominal load, limit load, breaking load
The nominal load of a load cell indicates the maximum weight to be applied or the force acting on the DMS load cell. However, we recommend using only approx. 70% of the nominal load. For a load cell with a nominal load of 100 kg this would be 70 kg, for a cell with a nominal load of 50 kg it would be 35 kg. If a weight above the nominal load is applied up to the limit load of the scale or load cell, the load cell may be permanently destroyed. The breaking load represents the value at which the material of the load cell can break, which then also permanently destroys it. Ultimately, compliance with these values also represents a safety aspect that must be observed.
The various load ranges of a load cell or scale are specified in the documentation and must be observed to ensure trouble-free operation. In the case of a scale, not only the load cell, but also the design must be considered accordingly.
DMS load cells are divided into classes according to OIML R60 according to their accuracy. In addition to class C, there are also classes A, B and D. We offer load cells with the accuracy of class C, which is further subdivided according to the number after C. This results in the following classes and division values:
Class C1: 1,000 division values
Class C2: 2,000 division values
Class C3: 3,000 division values
Class C4: 4,000 division values
Class C5: 5,000 division values
Class C6: 6,000 division values
Our range includes the standard with class C3, which is usually used in commercial scales and scales with a platform. A higher resolution scale is often used in multi-range scales and uses class C4 load cells. When the highest precision is required for the desired applications, a class C6 load cell is installed. With a 6,000 division, this creates twice the resolution as the frequently used class C3 in custody transfer applications. The C6 load cells also show their strengths in multi-range and multi-division scales. They are the cells with the highest possible resolution in this accuracy class and in our range.
In mechanical and plant engineering, it is often particularly important to obtain high-precision measurement results. If our load cells of accuracy class C6 are combined with the corresponding evaluation electronics, resolutions of 10,000 d can be achieved. In addition to the values of the weighing technology, the installation situation of the load cell must be taken into account, since this has an influence on the accuracy that should not be underestimated.
A platform in which a C6 strain gauge load cell is used achieves a calibration value of 0.5 g at a nominal load of 3 kg, while a platform in which a class C3 cell is used achieves a calibration value of 1 at the same nominal load g reached. Weighing technology with DMS load cells of accuracy class C6 stand for precision in perfection.
Installation and construction
Adequate rigidity must be ensured when designing a balance. This must not deform, as this would falsify the measurement result. Depending on the installation situation, it must be ensured that there are no force shunts. If, for example, a platform were to rest on one side, this would remove the possibility of deformation of the spring body and thus falsified measurement results would be output. With silo and tank scales in particular, care must be taken to ensure that any pipelines and the like are decoupled.
With platforms, overload protection can be a useful precaution to avoid damage to the load cells. This can be implemented relatively easily in terms of construction, for example by means of an adjusting screw, which prevents deformation beyond the nominal load.
Our floor scales are manufactured in a particularly high quality. The material used has a high strength according to the nominal load and is welded in Germany by qualified personnel in compliance with all quality standards into a constructive masterpiece. It's understandable that we only use our best load cells here. When using individual components of weighing technology, it should be noted that the worst used component of a balance represents the highest possible accuracy of the entire system. If load cells of class C3, or even without class allocation, for example with labels such as G3, 0.03 or similar, are used, a maximum of 3,000 divisions can be achieved in custody transfer. Load cells without approval must not be used in legal-for-trade traffic. But you should also pay attention to quality and trust the approval according to OIML R60 even in non-calibration traffic, where a resolution twice as high is often achieved.
Degrees of protection
Like many technical components, load cells are also assigned to a degree of protection according to ISO 20653 or DIN EN 60529. This specifies the requirements for possible use with regard to the tightness against dust, contact and water. The representation is "Protection class IPxx", where xx stands for a combination of numbers.
The first number provides information on protection against foreign bodies and contact. For load cells, this is usually 6, i.e. complete protection. This is due to the construction. It is a metal body in which the strain gauges are installed on the inside, covered with a filling compound (usually silicone) and, in many cases, also provided with a metal cover that is welded with a laser.
The second digit represents protection against water. For load cells, a protection level of at least 7 - protection against temporary immersion - should be achieved. This also enables more complex cleaning. Depending on the application, it can also be used outdoors. The IP protection class IP69 or IP69K is mandatory for the food and chemical industries, since cleaning with high-pressure and steam cleaners is also possible here.
Weighing technology also requires extensive testing as part of a certification process in order to ensure safe and legal use that is permitted in the first place. Load cells go through this test process and then receive approval for use in the EX-protected area. The protection class in relation to the desired application must be observed. Further information on ATEX use can be found in our dedicated area.
Load cells buy from OMEGA Waagen GmbH
Whether load cells, scales or weighing technology - in our extensive range, which is constantly being expanded, you will find everything to meet your requirements. Load cells of accuracy class 6 for high-precision applications and class C3 for normal requirements at a fair price. Most items are in stock - ordered today, tomorrow at your place.
Our competence is your gain. If our product range does not meet the application you require, contact us directly! We are looking for a tailor-made solution and would be happy to manufacture a special solution for your specific application. We also use weighing technology from a strong partner to complete our product range. Together with him, we can meet almost any requirement.
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We look forward to your order or your inquiry by phone (0 44 47) 96 94 63 - 0 or at any time by email at email@example.com!