Optics Valley Technology: What do electronic weighbridges need to do to prevent lightning strikes? Seek an answer

1. electrostatic induction, that is, the change of electrostatic field in the ground atmosphere caused by lightning, causes the conductor near the lightning object to generate induced charges, which constitutes a very high potential difference to the ground;

The second is electromagnetic induction, that is, the current in the lightning channel changes with time, forming a changing electromagnetic field in the surrounding space, and generating induced voltage and eddy current on the conductive objects in the channel accessories;

Third, the current in the lightning channel changes rapidly to form electromagnetic radiation. Because the electronic weighbridge can only bear low voltage, the above three physical processes caused by lightning are extremely destructive to it, especially electromagnetic induction. The more advanced microelectronic equipment, the less power consumption, the more sensitive it is, and the more destructive it is.

Therefore, the electronic weighbridge should do the following work to prevent lightning strikes:

First of all, a lightning rod should be set near the scale body to neutralize the charge in the cloud through the tip discharge effect, so that the electronic weighbridge will not be damaged by lightning. The height of the lightning rod can be determined according to the length of the electronic weighbridge, and the lightning rod protects a circular area with a radius equal to its height.

Second, the whole platform should be grounded, and the scale body should be connected to the grounding pile with one or several grounding cables. The grounding pile should be in the zero zone, with constant potential and grounding resistance less than 4 ohms. There is a spacious large current return channel between the weighing platform and the grounding pile, so when electrostatic induction occurs, electrons can be supplemented from the earth to neutralize it, and the equipment can be quickly evacuated without damaging the electronic weighbridge after high potential is generated.

Three, each sensor should have protective grounding. Therefore, each sensor position should be provided with a grounding wire, and a grounding pile should be provided between the sensor and the ground. The grounding wire shall be reliably connected with the grounding pile or with the nearby anchor bolts. However, the anchor bolts must be connected with the steel bar grounding net in the foundation.

Four, wear signal cable metal threading pipe must also be connected to the grounding grid.

Five, the shielding layer of the signal cable of the weighing sensor should be grounded. When the electronic weighbridge is powered by commercial power, there is a long space distance from the distribution room to the installation site, and there is also a relatively long signal cable from the scale platform to the scale room. It is not difficult to imagine that lightning strike may produce high potential on the conductor through electromagnetic induction, thus causing damage to the weighing instrument. Therefore, the signal line of the weighing sensor and the current power line that excites the weighing sensor are connected by the cable with the shielding layer grounded, so as to eliminate the possibility of damage or explosion caused by electromagnetic induction lightning strike. The shielding layer of the signal cable of the weighing sensor can be connected with the grounding wire of the weighing sensor or the grounding pile of the weighing display; It can be determined according to the site conditions, but it is not allowed to connect two grounding piles at two points respectively.

Six, weighing display instrument shell to the ground. Therefore. The ground scale house is equipped with grounding piles, which are connected with the steel mesh (grounding) in the scale foundation. When using a plastic shell, a metal film should be sprayed on the inner surface of the shell before grounding.

Seven, the junction box should be grounded. The junction box shall be equipped with a grounding wire connected to the scale body.

Eight, the power supply should be grounded, and at the same time should be equipped with a surge protector.