The grounding of electrical equipment is an important measure to ensure the safe and stable operation of the electrical system. Grounding is an essential method to prevent electromagnetic interference and lightning strikes, and it is of vital importance for enhancing the safety and reliability of the system. Yes. Grounding can protect human safety and ensure the stable operation of the system.
At the same time, it can enhance the system's anti-interference ability and anti-static damage resistance. This
In addition, grounding can effectively prevent damage to electrical equipment caused by lightning, ensuring the stable operation of the equipment under adverse weather conditions.
Load cells have been widely and deeply applied in various industries. Currently, the vast majority of load cells are installed outdoors, and they inevitably encounter the influence of thunderstorms and lightning. For the load cell system, grounding is indispensable because it can withstand surge currents and protect key components such as weighing sensors, instruments, junction boxes, and signal cables from damage. Moreover, grounding can effectively prevent phenomena such as weighing instrument drift, jumps, and damage to weighing sensors caused by lightning strikes and electromagnetic interference. Therefore, grounding plays a crucial role in the normal operation of the load cell weighing system. The common grounding methods for load cells are as follows:
a. Shielding grounding: This involves adding a shielding metal layer outside the conductor and connecting the shielding metal layer to the grounding electrode to prevent induced electricity from affecting the weighing sensors and instruments.
b. Bonding grounding: This grounding method involves using a single wire to connect the weighing sensor installation position to the weighing sensor base plate. The purpose is to guide the accidental electrification of the weighing platform across the weighing sensor into the grounding electrode of the base plate. This grounding method is convenient and therefore the most common.
c. Lightning rod grounding: This involves installing a lightning rod at the installation site of the load cell to prevent damage to the instrument caused by lightning strikes.
In engineering practice, the actual situation of the load cell installation site is often comprehensively considered to select one or several grounding methods. Today we
The reliability of the cross-connection grounding method is the main topic of discussion.
1 
The problem is raised
The most common grounding method for the weighing platform of current automotive scales is: near each weighing sensor installation position, a wire is used to connect the weighing platform to the base plate of the weighing sensor, and the base plate of the weighing sensor is connected to the grounding electrode, as shown in Figure 1. Is this grounding method reliable? I
We would like to express our own opinions on this matter. 1
Figure 1 Schematic Diagram of the Cross-Connection of the Scale Body
2 
Theoretical Analysis
The electrical schematic diagram of the grounding method mentioned earlier is shown in Figure 2.
(Where R1
represents the resistance of the grounding wire, and R2
represents the resistance of the elastic body of the weighing sensor). From the figure, we can see that the grounding wire plays a shunt role, which diverts the electricity carried by the scale body due to accidental reasons to the grounding electrode. If the resistance R1
of the grounding wire is much smaller than the resistance R2
of the elastic body of the weighing sensor, then the grounding wire can share most of the current and play a better protective role. If the resistance R1
of the grounding wire is not much different from or even greater than the resistance R2
of the elastic body of the weighing sensor, then it can only play a shunt role and is difficult to effectively protect the weighing sensor. Therefore, we conducted an experiment to determine which one is larger, the resistance of the grounding wire or the resistance of the elastic body of the weighing sensor.
3 
Test Overview
Since the resistance values of the grounding wire and the elastic body of the weighing sensor are both relatively small, it is difficult to directly measure their resistance values with a multimeter. Our test method is shown in Figure 3. R1
R2
R
Figure 3 Schematic Diagram of Testing Method
Connect to the scale body R1 R2
Figure 2 Grounding schematic diagram
We connect the grounding wire R1
in parallel with the elastic body R2
of the weighing sensor.
Then, we connect a test resistor R3
with a larger resistance value in series with it.
We supply power to the circuit using a direct current power source, and then measure the current passing through R1
and R2
separately. Flow.
The grounding wire used in the experiment was a 10mm2 braided copper wire. We weighed the sensors. We selected two manufacturers' bridge-type weighing sensors and two manufacturers' column-type weighing sensors respectively. We installed them on the entire vehicle. 2
The test was conducted on the automatic vehicle scale. The test results showed that the current passing through the weighing transducer was actually greater than the current passing through the grounding wire. That is to say
It is stated that the resistance value of the elastic body of the weighing sensor is less than that of the grounding wire. Therefore, we believe that the currently most common method of connecting the weighing sensor body and the grounding electrode cannot provide good protection.
4
How to solve the grounding problem
We believe that during the design, manufacture, and installation of the truck scale, measures should be taken to increase the electrical resistance between the weighing sensor and the scale body. Figure 4 shows a design method for installing the weighing sensor. We add an insulating sleeve (the insulating sleeve is made of cloth-reinforced bakelite rods and machined) between the pressure head on the weighing sensor and the scale body. This insulates the weighing sensor from the scale body. The base plate of the weighing sensor is welded firmly to the foundation steel bar cage, and the steel bar cage is equipped with a grounding electrode. Outside the foundation pit, another grounding electrode is made and the scale body is connected to the grounding electrode with a grounding wire.
5 Conclusion
By adopting the method of adding an insulating sleeve between the weighing sensor and the scale body, and setting a separate grounding electrode for the scale body outside the foundation pit, our company has installed over 1,500 truck scales and achieved good results.
We have the following points of experience that we would like to share with you:
(1) The grounding electrode of the foundation reinforcement cage is made of 50mm×50mm×5mm angle steel with a length of 1.5m. It is usually buried below the reinforcement cage, and the number of burials should not be less than 5. Each angle steel is reliably welded to the reinforcement cage.
(2) The grounding electrode of the scale body is buried in a relatively damp place outside the foundation pit. It is also made of 50mm×50mm×5mm angle steel with a length of 1.5m. The number of burials should not be less than 3. The top of the grounding angle steel is welded with 50mm×5mm galvanized flat iron and introduced to the appropriate position in the foundation pit.
(3) In less damp areas (such as below the foundation pit), the grounding resistance of one angle steel is approximately (10-15) Ω; in more humid areas, the grounding resistance of one angle steel is approximately 6 Ω. Due to the different geological conditions in different areas, there will be some variations.
(4) After the grounding electrode is completed, the grounding resistance should be measured, and the grounding resistance should be tested regularly during operation to ensure compliance with regulations.