Abstract: Electronic truck scale is measurement equipment which widely applied to the coal,metallurgy and chemistry industries and so on. It is used in weighing staple material.For the cheat phenomenons with the robot during weighing and measurement of coal, this article introduces the cheat principlr and method about the electronic truck scale during weighing and measurement, and the effective measures of prevention cheat for the cheat method emphatically.
Key words: digital; electronic truck scale; prevention cheat
At present, Huaibei Mining Group has nearly 30 electronic truck scales for local sales, including 21 digital truck scales and nearly 10 analog truck scales. In recent years, with the rapid development of electronic weighing technology and the increasing requirements of coal users for coal weighing and measurement methods, digital truck scales are gradually replacing analog truck scales with their advantages of high precision and high stability. To a certain extent, it also reduces the occurrence of cheating. But because the coal market is optimistic in recent years and coal prices have risen, some criminals have installed electronic remote control devices on analog truck scales, stealing in the weighing and measuring process, and illegally profiting from them, which has brought significant economic benefits to enterprises. loss. The author now combines work experience and several incidents of cheating-induced failures that have been found and dealt with on-site, and introduces how to prevent cheating, for reference only.
- The cheating phenomenon of electronic truck scale
There are various cheating methods for electronic truck scales. This article only introduces the use of electronic remote control devices to cheat.
2.1 Composition of cheating device and cheating process
The device generally consists of three parts: transmitter, receiver and power supply. It is generally used when the front wheel of the car is just on the weighing platform, the thief turns on the remote control device, and after the weighing is finished, the remote control device is turned off when the rear wheel of the vehicle is about to leave the weighing platform.
2.2 Principles of Cheating
The working principle of the device is to connect a resistor in series with the output/input signal cable of the internal measurement circuit of the load cell, causing the output signal to decrease, so as to achieve the purpose of reducing the weighed weight. According to the cheating phenomenon discovered by the author in recent years, the general theft device is installed in the signal cable of the load cell, the weighing display instrument and the junction box. The following focuses on the phenomenon of cheating by installing a theft device in the signal cable of the load cell.
When the electronic truck scale is installed, the signal cables of several weighing sensors outdoors are connected to the junction box through the conduit, but a part of the signal cables are still exposed. This small piece of signal cable gives some criminals a chance. Enticed by profit, they will look for opportunities to peel off one of the load cell signal cables and disconnect the excitation voltage positive (+EX) line of the load cell. If the sensor is connected in a six-wire system, it will be disconnected at the same time. The feedback voltage positive (+F) line, after disconnecting, connect the remote control receiver in series to the excitation voltage positive (+EX) line. At the scene, we also found that the receiving device was connected to the signal line (+Si or -Si) in series. After the theft device is installed, it will generally not affect the normal use of the electronic truck scale. Only the criminals turn on the remote control tens of meters away from the scale body. The resistor is connected in series to the excitation voltage positive (+EX) line or the signal line (+Si or –Si), which causes the power supply voltage of the weighing sensor’s Wheatstone bridge to decrease, or the signal line is connected to the resistor in series to make the output millimeter The reduction of volt-level electrical signals will ultimately result in a reduction in the weight of the truck scale. This theft method is highly concealed, easy to operate, and difficult to detect.
A remote control device is installed in the weighing display instrument, usually before the A/D converter of the instrument, and the resistance value of the weighing instrument is adjusted by remote control to adjust the weighing value of the weighing instrument.
- Anti-cheating of electronic truck scale
Theft devices not only reduce the weighed weight, but also bring economic losses to the enterprise; some theft devices often cause weighing system failures due to their own quality or installation problems and cannot be properly weighed. In order to protect the legitimate interests of the enterprise, reduce unnecessary economic losses, and not give the criminals a chance to take advantage of it, the enterprise can take effective methods to prevent illegal acts of theft using remote control devices. In addition to strengthening management, increasing the sense of responsibility, and opening the cover and junction box on the scale body for inspection from time to time, the following measures can also be used to prevent theft:
3.1 Protection of load cell cables
When the load cell of the electronic truck scale is installed, its signal cable is connected to the junction box through the threading tube, but there is still a small part exposed outside the threading tube. The criminals use this part of the exposed cable to peel off the skin and install the remote control. The device was stolen. Therefore, we can consider using plastic-coated hose or stainless steel hose for protection between the load cell and the threading pipe. One end of the load cell is connected with a wire joint, and one end of the metal threading pipe is also threaded to prevent signal cables. The remote control device is exposed and destroyed in series.
3.2 Adopt digital truck scale
Digital truck scale adopts digital weighing display instrument and digital weighing sensor, and its signal transmission adopts digital communication technology, bus structure, and RS485 interface to realize long-distance signal transmission. Because the load cell uses digital signal transmission, and the digital signal transmission is carried out according to different communication protocols specified by different manufacturers, to cheat on the signal transmission of the digital load cell, the communication protocol of the manufacturer’s digital load cell must be deciphered Only possible, therefore, the possibility of cheating on a digital truck scale is very small. At present, weighing display instruments produced by some manufacturers can detect digital sensor signals in real time and have anti-cheating functions.
- Concluding remarks
With the in-depth development of the Huaibei mining area, electronic truck scales are used more and more as the main equipment for coal sales, weighing, measurement and trade settlement in the mining area. Its technical status is good or bad, and whether its measurement performance is in line with national technology. The requirements directly affect the economic interests of the enterprise. For this reason, we must attach great importance to the phenomenon of some criminals using various means to cheat, further strengthen management, and take effective measures to overcome it, so as to ensure the normal progress of coal sales weighing and measurement work, and to maintain the company’s economic benefit.
 Zhang Fang, etc., on cheating and anti-cheating of electronic truck scales, “Weighing Apparatus”, Issue 4, 2003