Weighbridges: Reliable weighing solutions for industry and agriculture

A truck scale is a weighing system that is used to weigh the load of a vehicle. It is mainly used in recycling plants, factories, quarries and agriculture. Generally, a truck scale uses a structured platform made of metal/concrete, solid concrete or solid steel with load cells and a control transmission system to display the total weight of the vehicle and the goods loaded on it.

Various aspects should be considered when purchasing and using a truck scale. In the recycling industry, for example, the vehicles are generally longer, goods such as stones or paper spill and impair the function of the truck scale. Access and cleaning requirements under the truck scale are therefore important. If the value of the goods to be weighed is high, the requirements for the accuracy of the load cells for the truck scale also increase. In agriculture, on the other hand, the requirements for the width of the vehicles are different and, of course, the requirements for overload protection of the truck scales are high. In companies located near the ocean or sea, for example, there are requirements for water and corrosion protection. In the logistics and warehousing industry, where the truck scales are part of the factory's overall IT system, which is often linked to purchasing, storage and sales systems, there are many vehicle entries and exits, which requires fast measurements and high traceability functions.

As with most scales, the main central component of a truck scale is the load cell, usually between 4 and 8 load cells, depending on the number of modules on the platform. The load cells are mounted under the lower part of the truck scale platform using a mounting kit. The signal cables of the load cells are connected to the weight indicator via a junction box to display the weight. In addition to these basic elements, the truck scale can be equipped with a second indicator, the so-called weight repeater, depending on the user's needs, a system that ensures that the driver can check that the truck scale is at zero and that he can see his weight when he is standing on the scale. Other devices, such as weighing terminals, can independently control the management and recording of weighing operations.

The location of a truck scale must be carefully considered: Is the surface strong enough to bear the weight of the scales and the loaded lorry? Does the weighbridge have to cope with traffic in one or both directions? Does the site provide adequate drainage for rainwater? Does the site provide enough space for lorries to enter and exit the weighbridge without problems? Is the site large enough to add a new weighbridge if required? Is a waiting area provided so that waiting lorries do not block traffic on the carriageway? You need to know the compressive strength of the soil, frost and water levels at the installation site and make sure that the chosen location is suitable for the installation before you draw up the exact construction plan. The load-bearing capacity under the foundation of the weighbridge varies between 7,300 kg/m2 and 12,200 kg/m2. If the site conditions do not fulfil this requirement, reinforcement must be provided. The foundation of the vehicle bridge must be excavated deeper.

Do not install the device in the vicinity of strong sources of interference, such as post and telecommunications offices, television towers, large transformer stations and high-voltage power lines. Electromagnetic and electrostatic couplings cause interference with the load cell signals transmitted by the transmission cables, and the longer the signal lines, the stronger the interference.

When the truck scale is moved, the forces acting on it cause the load cell to deflect. The restoring force ensures that the load cell returns to its centred rest position as quickly as possible.

The PR 6221 truck scale load cells fulfil the requirements

• Lightning impulse current (Imax = 100 kA) 10 µs/350 µs (lightning protection class III) according to DIN EN 62475
• Lightning impulse voltage (Umax = 1,000 kV) 1.2 µs/50 µs according to DIN EN/IEC 60060-1

With quality overvoltage protection, equipotential bonding, protection of the measuring cable and in conjunction with Minebea Intec cable boxes and indicators, the analogue load cells can withstand voltages of up to at least 1,000 kV and currents of up to 100 kA without damage.

The output resistance (Ro) and characteristic value (Cn) of the load cells are within a narrow tolerance band individually and in combination (= matched output). This eliminates the need for electrical corner adjustment and only mechanical height compensation is required.

A calibrated indicator is a display system that is calibrated and verified in accordance with legal requirements. It is used in conjunction with truck scales to display accurate weight information.

The total weight of a vehicle is crucial for road safety and compliance with weight restrictions. It is therefore very important to determine this weight accurately and reliably.

The surface is of great importance as it influences the stability of the weighbridge. A level, firm and stable surface is necessary to ensure accurate weighing results and the longevity of the scale.

There are different types of weighing systems, including stationary truck scales, mobile weighing systems and axle load scales. Each system has its own advantages and disadvantages, depending on the requirements and usage situation.