Practice has shown that weighing sensors with smaller ranges are more prone to overload than those with larger ranges. For example, just if a wrench falls, a weighing sensor with a range of 20 kg will be overloaded. Therefore, overload protection is required for the weighing sensor.
1. Mechanical limit
The following diagram is a design scheme for overload protection of cantilever beam type weighing sensors. Protected by mechanical limit devices.
Take the displacement when the sensor is loaded at full range as the additional displacement. It is recommended to save an additional displacement of 120-150% for the gap of overload protection. This distance can be adjusted through a distance meter, but due to the very small deformation (only a few 1/10 mm in reality), it is usually adjusted after loading.
Other measures should be taken to avoid contamination between the limit point and the sensor, as contamination can cause unnecessary measurement errors.
If the support structure of the weighing sensor is soft, the overload equipment will be protected in advance due to deformation after loading. Therefore, the distance between the limit and the sensor should be increased, with a gap of approximately 0.05 to 0.1 mm.
2. Spring structure
Another way of overload protection is achieved through prestressed springs (as shown in the figure below). If the range exceeds a specific value, the spring will be compressed and limited to a strut.
The gap width of this overload protection device is larger, which makes loading simpler and more reliable (the spring expands the deformation displacement). And the characteristics of the spring can reduce the damage caused by pulse loads. Due to the lower sensitivity of spring limit devices to pollution, most static/quasi-static weighing methods are used.