Dividing the target capacity by the number of cells alone is not sufficient in platform scale design. Chassis tare, off-center loading, impact, safety margin, platform deflection, and load cell installation direction must be calculated together. Proper mechanical design comes before high-resolution electronics.
Design inputs
Maximum net load, platform size, how the product will be loaded, daily cycles, ambient temperature, washing, and target division are determined. Load left by a forklift and fixed load placed by hand do not have the same dynamic coefficient. If used commercially, metrological requirements must be added to the plan from the beginning.
How is the total load cell capacity calculated?
In the preliminary calculation, the maximum net load is collected with the tare of the platform; an appropriate safety factor is applied for dynamic and off-center load effects. The result is divided by the number of cells. However, in the worst-case scenario, the load that could come to a single corner is also checked separately.
For example, in a four-cell scale with a platform tare of 300 kg and a net capacity of 1500 kg, the static average cell load is 450 kg. Placing the pallet in one corner, due to impact and uneven distribution, selecting a 500 kg cell may be borderline. Actual coefficients should be determined according to the mode of use and manufacturer data.
Why is platform deflection important?
If the chassis bends too much under load, the force is not transmitted properly to the cells, corner values change, and hysteresis may occur. The beam section and layout should be verified by finite element analysis or an appropriate engineering method. Load application points should create a logical load path for the cell axes.
Which type of load cell should be used?
Single point load cells can be practical on small and medium platforms thanks to off-center load compensation. For larger platforms, shear beam or double shear beam cells and suitable mounting kits may be preferred. The choice depends on platform size, accuracy, environment, and lateral forces, as well as capacity.
Assembly details
- All load cell surfaces must be in the same plane.
- The cell should not be subjected to torsion or lateral preload.
- Assembly bolts should be tightened according to the manufacturer’s torque.
- The cable must be protected against crushing and pulling.
- Overload stops should not prevent the measuring movement.
- The ramp or surrounding chassis must not touch the platform.
Connection box and corner adjustment
In four-cell systems, the connection box collects signals and allows for corner balancing. Adjustment is done by applying the reference load to each corner in the same way after checking the mechanical assembly. A large electronic correction requirement often indicates mechanical inequality.
Resolution and accuracy
Selecting a very small division on the indicator does not guarantee actual accuracy. The minimum verification range of the load cell, indicator input sensitivity, cable, vibration, and platform performance should be evaluated together. In OIML applications, certificate parameters are included in the system calculation.
Calibration sequence
- Empty platform and mechanical freedom check
- Zero adjustment
- Corner test and balancing if necessary
- Span/linearity check at multiple load points
- Return to zero and repeatability after unloading
Common design errors
Selecting the cell solely based on the nominal load, forgetting the tare of the chassis, not accounting for forklift impact, giving up on the assembly kit, and leaving the cable unprotected under the platform are the most common issues. Additionally, even the sheet metal coating in contact with the environment can affect the weighing result.
Frequently Asked Questions
Can the capacities of four load cells be added together?
Mechanically, yes in terms of total carrying capacity; however, the safe scale capacity is determined by considering load distribution, tare, dynamic effect, and the worst load of each cell.
Can a platform be made with a single load cell?
It can be made with a single point load cell if the platform size and capacity are suitable. The platform dimensions allowed in the datasheet should not be exceeded.
Is a stainless steel load cell necessary?
It may not be necessary in a dry environment. In washing, humidity, chemical, and hygiene conditions, the body and IP protection class are selected accordingly.
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explore industrial scale solutions and load cell options and for a custom design you can get support from Kobastar.