Urgently need the operating methods or procedures for electronic truck scales

A new factory is being built, with two weighing rooms. I’m not sure which department will be in charge of them in the future, so I’ll start by learning about it first

Electronic truck scales 1 Overview: Truck scales are considered **measuring instruments subject to mandatory calibration. After each maintenance or adjustment, they must pass inspection by a qualified legal metrology institution before they can be used. 1.1 System Composition The SCS series of electronic vehicle scales typically consist of components such as the weighing platform, load cells, connectors, limit devices, wiring boxes, and weighing display instruments. Depending on the application requirements, external devices such as printers, large-screen displays, computers, voltage stabilizers, and UPS systems can be added. 1.2 Working Principle: The object to be weighed or the truck is placed on the scale platform. Under the action of gravity, the platform transmits this force to the load-bearing supports, causing the elastic element of the weighing sensor to deform. This deformation disrupts the balance of the strain gauge circuit attached to the elastic strain beam, resulting in an electrical signal that is proportional to the weight. This signal is amplified by a linear amplifier, then converted into a digital signal by an A/D converter. The microprocessor (CPU) in the instrument processes this signal and displays the weight value directly; the weighing data is also printed out using a printer. If a computer is configured, the measurement data can be entered into a computer management system for comprehensive management. 2 Technical Specifications 2.1 Main technical specifications of vehicle scales 2.1.1 Maximum weighing capacity: 120T. 2.1.2 Counter size: 3.4×18m. 2.1.3 Accuracy class: Grade III – 0-500e ±0.5e (0-20T ±20kg); 500-2000e ±1e (20-80T ±40kg); >2000e ±1.5e (>80T ±60kg). 2.1.4 Maximum division: n=3000. 2.1.5 Verification division value: e=40kg. 2.1.6 Displaying the division value: d=20kg. 2.1.7 Operating environment: Temperature of -10~45°C, relative humidity not exceeding 95%RH. 2.1.8 Power supply: 220VAC(-7%~+7%) 50Hz. 2.1.9 It features functions such as zero setting, automatic zero tracking, power-off data protection, and self-diagnosis of faults. 2.2 Main technical specifications of the sensor 2.2.1 Maximum range: 40T. 2.2.1 Sensitivity: 2mV/V. 2.2.2 Comprehensive error: ±0.03%. 2.2.3 Safe overload: 150%. 2.2.4 Input impedance: 375±1Ω. 2.2.5 Output impedance: 370±1Ω. 2.2.6 Insulation resistance: ≥5MΩ. 2.2.7 Safe side load: 100%. 2.2.8 Extreme overload: 400%. 2.2.8 Number of sensors: 8. 3 Inspection and Debugging 3.1 Inspection Items 3.1.1 The sensors and extension cables are intact, with no oxidation or rust at the connections. 3.1.2 The central junction box is intact, with no deformation or poor sealing. 3.1.3 The shielding layer of the signal cable must be properly grounded, and the insulation resistance between the signal wires with respect to ground must be greater than 5 MΩ. 3.1.4 The weighing display unit is in good condition, with correct wiring and no looseness. 3.1.5 The weighing platform of the vehicle scale is free from deformation. 3.2 Preparations before debugging 3.2.1 Bring debugging weights, lifting equipment, and forklifts to the site. 3.2.2 Be familiar with the operating instructions of the weighing display. 3.2.3 Power on the system and let the instruments warm up for 15 minutes. 3.2.4 Debugging sequence: All parameters of the vehicle scale are set and calibrated according to standards at the time of manufacture. Upon arrival at the site, offset adjustment and zero-point adjustment are carried out first, followed by fine tuning of the measurement range. Generally, no re-setting or recalibration is required; however, if components such as sensors, center plates, and weighing displays are replaced, re-setting and recalibration are necessary. 3.2.4.1 Unbalance adjustment (angle difference adjustment) Unbalance adjustment can be performed once the instrument enters the weighing mode. Use weights of a certain weight (usually one-fifth of the maximum capacity) to apply pressure to the corners in sequence, so that the display values for each corner do not exceed the allowable error. If the error exceeds this limit, it can be adjusted by modifying the corner coefficients until the readings for all eight corners are consistent. The adjustment of the octagonal coefficient can also be accomplished by automatically adjusting the angular coefficient. 3.2.4.2 Zero-point adjustment: After the first installation or maintenance of a vehicle scale at the site, it is necessary to reset the zero point. When the scale platform is empty, press the “Zero” button, or go to the menu to perform zero calibration. 3.2.4.3 Range Adjustment Range adjustment essentially involves adjusting the linear slope. As shown in Figure 6-3-1, if the actual input display value is as indicated by the dashed line, the range adjustment function of the instrument can be used to make the output follow a linear pattern, as shown by the solid line in the figure. The steps for fine-tuning the range are as follows: a. Before using the range adjustment function, it is necessary to first set up standard calibration. Although the minimum value of the test weights does not need to be more than 10% of the full scale, in practice, as many weights as possible should be used. b. Enter to perform zero-point calibration. c. Load a known silicon weight on the scale platform to perform range calibration. 4 Maintenance and Fault Inspection 4.1 Allowable Axle Load 4.1.1 The maximum load of vehicles exceeding the scale limit shall not exceed the maximum weighing capacity of the scale. 4.1.2 The axle load permitted for vehicles weighing on the truck scale is 40T. 4.1.3 The allowable load on the weighing axes of a vehicle scale is related to factors such as the sensor capacity and the distance between the sensor supports; generally, vehicles such as forklifts that are close to their maximum loading capacity, as well as vehicles with short wheelbases, are not allowed to be weighed on such scales. 4.1.4 When the vehicle approaches the scale platform, its speed should be below 5 km/h; it should drive straight onto the platform and then brake gradually. Once the vehicle has come to a complete stop, weighing can take place, with the vehicle staying as close as possible to the center of the scale platform. 4.2 Weighing platform maintenance 4.2.1 The gaps around the weighing platform should be even and appropriate (10~15 mm), and there should be no foreign objects such as stones or metal pieces stuck in them. 4.2.2 Regularly check that the limit clearance remains at 2~3 mm, and the limit bolts should not come into contact with the scale body. 4.2.3 The connectors shall be maintained every six months, with butter applied to the support heads. 4.2.4 Regularly clean the surface of the scale platform to keep it clean; the paint on the surface should be repainted periodically (it is recommended to do this once a year). 4.2.5 Arc welding is prohibited on the scale platform. If arc welding must be carried out on the scale platform, please pay attention to the following points: a. Disconnect the signal cable from the instrument. b. The ground wire for arc welding must be placed near the area to be welded and in firm contact with the scale body. c. The sensor must not become part of the arc circuit. 4.3 Instrument Maintenance 4.3.1 The instrument generally requires about 15 minutes of warm-up time after being turned on; it is strictly prohibited to connect the instrument’s power supply while the weighing platform is under load. 4.3.2 Regularly check whether the wiring is loose or broken, and whether the grounding wires are secure. 4.3.3 Keep the junction box dry and clean; the desiccant inside should be replaced regularly. If moist air or water gets into the junction box, it can be dried using a hair dryer. 4.4 Sensor Replacement: Once a damaged sensor is detected, follow these steps to replace it: a. Open the cover plate located above the damaged sensor on the scale platform, use a jack to lift the platform, remove the connecting components, and if there are limit supports, take them off as well. b. Open the junction box, disconnect the damaged sensor cable from the junction box, remove the cable clamps that hold this cable in place, and pull the cable out at the sensor end. c. Use a socket wrench to loosen the high-strength nuts that hold the sensor in place, remove the old sensor, install a new one, secure it with high-strength bolts and nuts, and then tighten the nuts using a torque wrench to the specified torque. The required tightening torque for the sensors used in truck scales is shown in Table 6-3-6. Table 6-3-6: Table of specified tightening torques for sensors. Sensor capacity/T: 30. Bolt specification: M24. Tightening torque: N•m – 450; Kg•m – 45. d. Pass the new sensor cable through the scale body into the junction box, and secure the cable using cable clamps. e. Fix (or solder) each core of the cable to the corresponding terminal or solder joint in the junction box. f. Install the connectors (apply butter to the support heads) and the limit supports, release the jack, level the weighing platform, and cover it with the lid. g. After replacing the sensor, the truck scale must be recalibrated; details are provided in section 3.2.4.3 of this document. 4.5 Replacement of the instrument PCB board: For truck scales that are used frequently, if the instrument gets damaged and it is difficult to identify the fault immediately, the instrument’s PCB board can be replaced quickly in order to avoid disrupting the use of the scale. The steps to replace the PCB motherboard are as follows: a. Cut off the power to the instrument. b. Turn on the instrument, disconnect all connectors on the PCB, and note down their locations. c. Remove the screws that hold the PCB board in place, and take off the PCB board. d. Install the new PCB board (placing the shielding layer in its proper position as well) and secure it with screws. e. Insert the connector in the correct position. f. After installing a new PCB board, the parameters must be reset and calibrated again. 4.6 Fault Inspection 4.6.1 Locating the Fault Location When a vehicle scale stops working due to a fault, it is first necessary to determine where the fault lies. The simplest way to do this is by using a simulator; the steps are as follows: a. Disconnect the signal cable from the junction box to the instrument, and insert the connector of the simulator (a nine-core D-shaped flat connector) into the instrument’s interface. b. Connect the power supply and check whether the instrument is working properly. If the instrument functions normally, the fault lies in the weighing platform; if it does not work properly, the fault is with the instrument itself. 4.6.2 Scale platform fault analysis a. First, check the junction box for any signs of moisture intrusion; if there is moisture, clean it with alcohol and then use a hair dryer to clean the interior. b. Check for any short circuits in the wiring; inside the junction box, use a multimeter to measure the resistance between the shield wire (sh, yellow) and all other wires as well as the scale platform, to determine if there are any short circuits. Also check whether there are any short circuits between each wire and the ground wire or the stainless steel shield wire surrounding the signal cable. If any short circuits are found, the cable needs to be replaced; if no faults are detected, then check the sensor. 4.6.3 Steps to identify sensor faults: a. Inside the junction box, disconnect the sensor wires, and use a multimeter to measure the resistance between the positive excitation (+EX) and negative excitation (-EX) terminals of each sensor; this resistance should be around 770Ω. Also, use the multimeter to measure the resistance between the positive output (+Sen) and negative output (-Sen) terminals of each sensor, with this value being approximately 700Ω. If the resistance values are not correct, proceed to the next step to continue troubleshooting. b. Place the weights on each cross-section of the scale platform in turn; if it is found that the reading for a particular cross-section is incorrect, place the weights at the various corners of the sensor located on that cross-section (at the pressure points) to identify the faulty sensor, and replace it in accordance with section 4.4 of this document. Alternatively, disconnect the +Sen and -Sen terminals of a sensor and measure its resistance value when no power is applied; this value should be around 700Ω. When power is applied, measure the DC voltage across those terminals. If the sensor’s capacity is K and the actual pressure it experiences is F, then using an 8142 instrument, the voltage value will be: U=U0*S*F/K (mV), where U0 is the excitation voltage and S is the sensitivity of the sensor. 4.7 Common Faults and Solutions (see Table 6-3-7) Table 6-3-7 Common Faults and Solutions Common Faults Cause of Fault Solution No display on instruments upon startup Power supply not connected Check whether the power plug is properly inserted or if there is a break in the connection ； Check the fuse ； Check the regulated power supply ； Check the instrument power supply section ； Instrument damaged; replace the instrument. The displayed numbers are unstable and fluctuate; poor wire connections – check all wire connectors ； The regulated power supply does not provide proper output; use a multimeter to check the output of the regulated power supply ； The junction box is damp; use a hair dryer to dry it ； The sensor is faulty; see section 4.6.3 on instrument failures – replace the instrument. The weighing data displayed is suddenly far outside the acceptable range. The weighing platform is not moving smoothly due to foreign objects blocking the limits; check the gaps around the platform to remove any such objects ； Device failure: Adjust the clearance ； The sensor is faulty; see sections 4.6.2 and 4.8 for maintenance procedures. The calibration period for electronic truck scales is 1 year, and prior to calibration, the scales must be maintained and adjusted in accordance with the procedures specified in this document.

Great work, OP; it’s exactly what needs to be learned – excellent! Thank you first!

Why can’t I see the image? Did you ask on the 13th floor?

The maximum weight that modern truck scales can handle is 200 tons, and our company has many such scales

Reply to 3# denghl: Very good, I’ve saved it for future reference.

Good post, worth sharing. Learn* it a bit.