February 24, 2022

Load Cell Structure and Function

Load cells are used to measure weight and are an integral part of our daily lives. It can be seen everywhere, such as on supermarket counters or on highways. Of course, you usually cannot recognize them immediately because they are hidden in the instrument.


Load cells are usually composed of elastomers with strain gauges. The elastomer is usually made of steel or aluminum. It is very strong and has very little elasticity. As the term “elastic body” puts it, steel or aluminum undergoes a certain amount of deformation under load, but then returns to its original position and responds elastically to each load. These very small changes can be obtained with strain gauges. The deformation of the strain gauge is interpreted by analytical electronics to determine the weight.


To understand the last point, we need to explain strain gauges in more detail: they are electrical conductors that are firmly attached to the substrate in a meandering manner. When the substrate is pulled, it and the electrical conductor will be longer together. When it shrinks, it becomes shorter. This will cause the resistance in the electrical conductor to change. The strain can be determined on this basis, because the resistance increases with the strain and decreases with the contraction.


The strain gauge is firmly fixed to the elastomer, so it experiences the same movement. For the load cell, these strain gauges are arranged in the Wheatstone bridge. This means that four SGs are connected to form a bridge, and the direction of the force to be measured is aligned with the measurement grid.


If an object is placed on or suspended from the load cell, the weight of the object can be determined. The expected load of the load cell is always in the direction of the center of the earth, that is, the direction of gravity. That is, only the force component in the direction of the load’s gravity can be obtained. This is not the case with force sensors, although the design is similar. The force sensor can acquire loads occurring in all directions. It has nothing to do with the direction of the earth’s gravity and the installation method.


Compression force sensor

Compression force sensor

Curved beam load cell

Curved beam load cell

Single point load cell

Single point load cell

Pull towards the load cell

Pull towards the load cell

Load cell type


There are many types of load cells, suitable for different applications. Commonly used ones include:


Single-point load cell: Generally used in platform scales, which are placed under the weight.

Curved beam load cell: Multiple load cells are placed under the steel structure and load heavy objects from above.

Compression force sensor: A number of long-range load cells are placed under the steel structure and load heavy objects from above.

Tensile force load cell: The weight is suspended under one or more sensors.

Many load cells have other features, such as special designs or features, etc., depending on different applications, for example, if the system needs to be cleaned thoroughly every day. The load cell requires a higher degree of protection and tightness.


Load cells can also be classified according to the type of signal transmission: digital load cells have built-in electronic components that are used to process measurement results and display and transmit them. For analog load cells, additional equipment-a measuring amplifier is required.


The four strain gauges are fixed to the load cell below, and the maximum deformation occurs when force is applied. The direction of the arrow is the direction in which the force is applied.


The influence of environmental weighing sensors

A characteristic of load cells is that the environment plays a decisive role.


Ambient temperature

Each substance changes with changes in temperature, expands as the temperature rises, and shrinks as the temperature drops. The same applies to the load cell and its strain gauge, and it also affects the resistance of the conductor. However, regardless of the ambient temperature, in order to obtain correct measurement results, each HBM load cell has a built-in complex temperature compensation mechanism.


The load cell must be able to withstand various influences. “For a truck scale, it must be able to withstand various outdoor environmental impacts. On a worldwide scale, for example, in Siberia.


truck scale


Forces applied in other directions (“parasitic forces”)

Depending on the installation environment of the load cell, for example, the weighing container is placed under the conveyor belt, and other loads other than the weight may occur. The “parasitic force” will not only occur in the required main direction, but also be applied from the side and below. The load cell was not developed for this purpose, and the measurement results may be incorrect or erroneous. Therefore, care must be taken during installation to ensure that there are no or as few parasitic forces as possible.

Load cell application

The load cell is usually installed on the scale. But there are many other applications. Examples include bottling plants or bottling equipment, or sorting systems that distribute candies or potatoes into packages.


“Weighing technology is being expanded to more areas.”-Stefan Schmidt


And our load cells also have unusual uses. For example, our PW15iA single-point load cell is used to develop high-performance triathlon clothing and swimwear.



Load cell accuracy

No matter what kind of load cell is used, accuracy plays a very important role. The load cell has different maximum ranges (the maximum range refers to the maximum expected load) and accuracy levels. The accuracy levels of strain technology are generally C and D. Strain load cells with electronic correction have higher accuracy levels.


“Weight is dominant in the industry, because goods are sold mainly by weight.”-Stefan Schmidt


Therefore, weighing must be strictly controlled. For low-value goods (such as sand or gravel), the load cell does not need to be very accurate-D-level accuracy is sufficient. On the other hand, for pharmaceutical products, the highest precision grade A or B is required. The most common consumer products such as meat, fruits and vegetables are weighed with an accuracy class of C, which requires high accuracy for the weighing system used. But mechanical engineering or building materials weighing instruments also require C-level accuracy.


Strict weighing gauge standards continue to pose new challenges for load cell developers. For load cells with higher OIML accuracy levels, the accuracy deviation is only a few ppm (parts per million).


Adjustment, calibration and trade certification

In order to ensure that the load cell works in an on-site manner, it is usually not only adjusted and calibrated at the factory, but also certified at the installation location. If one kilogram is on the load cell, according to the accuracy class, the weight shown should also be 1 kilogram instead of 857 grams. In this way, adverse effects such as parasitic forces can also be detected.


Load cell technology trends

Strain-based load cells have a very wide range of applications. NingboGoldshine has more than 10 years of experience in the development of load cells, and constantly develops new solutions to meet future needs.


Strain weighing technology has not been fully utilized in many fields, but the trend has been determined-it needs to be more precise, stronger, faster, smarter, and easy to use.

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