Views: 12 Author: Site Editor Publish Time: 2024-08-21 Origin: Site
Truck scales are essential tools for industries that require accurate weight measurements for large vehicles. However, like any other equipment, truck scales can experience issues over time. Regular maintenance and prompt repairs are crucial to ensure the scales function accurately and efficiently. As a leading scale manufacturer and supplier in China, we have summarized some common errors associated with truck scales, as well as tips on how to repair and maintain them.
The display of the instrument is unstable, ranging from tens of kg to hundreds of kg.
The analog part of the instrument is damaged, the power supply is faulty, the signal changes caused by faults in the sensor, junction box, cable, etc., the weighing platform and the foundation are blocked by debris, and there is no gap between the limit bolt and the foundation.
The weighing error is large.
There are problems with the weighing platform and the foundation, the instrument is not accurately adjusted, the analog part of the instrument is broken, the sensor and junction box are problematic, there are errors in the four corners, etc.
3.There is no self-test when the truck scale is turned on
After the instrument is powered on, there is no display or only part of the stroke segment is displayed, and some are accompanied by buzzer beeps.
The external 220V power supply and the power supply circuit (line, fuse, internal transformer, three-terminal voltage regulator) are faulty, the instrument PCB board is damaged or the LED display tube is damaged or the connection line is detached.
4.No return to zero after power on or unloading
After the power is turned on, the meter displays a non-zero value after self-check, there is an error prompt or a relatively stable value is displayed, or a positive or negative value is displayed after the vehicle is unloaded during weighing, and the zero position is not displayed.
The amplification part of the meter is faulty, the sensor performance changes (hysteresis, drift, etc.), and there are debris blocking the scale body and the foundation.
5.No display on the display
The display quality window is completely dark, but the status light is on.
First check whether the power plug is firmly plugged in, whether the fuse is blown, whether the cable connection is broken, and whether the sensor input and output resistance meet the requirements. If the signal line of the junction box is broken, wipe it with alcohol, re-weld it, and the system will return to normal.
If the instrument is suspected to be faulty, the following methods can be used for judgment. First, use the simulator to connect to the instrument and observe the changes in the indicated value, such as whether there is a display, whether there is drift, etc. If the indicated value remains stable, it means that the instrument is faulty. Second, replace the spare main storage chip, input the original parameters into the new main storage chip, and use the same method to observe the changes in the indicated value to judge whether the instrument has a fault.
First, carefully observe the appearance of the sensor, such as whether the sealing cover falls off, whether the shell is obviously damaged, whether the base is broken, etc.
Secondly, it is necessary to check whether the sensor wires are connected, damaged, or broken. Measure the sensor resistance value. If the resistance value is abnormal, it needs to be replaced in time; measure the sensor millivolt signal. If there is a relatively large millivolt signal deviation between several sensors, the angle difference needs to be adjusted. After adjustment, if the fault is still not eliminated, it is necessary to stimulate the replacement of the sensor. Disconnect the sensors of the scale one by one, and observe the corresponding changes in the displayed values in detail. For example, if the original display showed drift, but the displayed value is now relatively stable, it means that the disconnected sensor is damaged.
Determine the resistance value: measure the resistance between ±Si (about ±5), measure the resistance between ±EX (same as above), and for the corresponding resistance value of the sensor, it is based on the nominal resistance value of the sensor actually used.
Measure the voltage value: measure the voltage value between ±Si of a single sensor, usually 0mV~25mV, and the empty scale is usually 0mV~5mV. Several sensors should have similar values in millivolt signals, and for the corresponding volt signal reception value of the secondary instrument, it is necessary to refer to the actual instrument used.
Determine the insulation performance of the sensor: On site, the digital multimeter can be temporarily placed on the 20M position, one end of the test rod is connected to the shielding wire or the shell, and the other end is connected to any one of {±EXC, ±SI}. If the value displayed on the multimeter at this time is 1, it means that the insulation resistance is infinite and the sensor is not faulty. Otherwise, there is a fault.
Carefully observe whether there is physical deformation on the appearance of the scale body, check the connection status of the connector, whether there is any jamming, and observe whether the limit is normal.
To see if it has good contact and whether there is any water vapor intrusion. If there is water vapor intrusion, use a hair dryer to dry it and fix the terminal. If the fault still exists, then the junction box needs to be disconnected for further investigation.
In the junction box, use a multimeter to measure the resistance of the shielded wire and other lines to check if there is a short circuit. If there is a short circuit, the original cable needs to be replaced immediately. If there is no fault, continue to search according to the following steps: First, in the junction box, use a multimeter to check the resistance between the negative excitation power supply (E-) and the positive excitation power supply (E+). The resistance is approximately the nominal resistance divided by the number of sensors. Secondly, disconnect the sensors one by one, use the above method to measure the resistance between the positive and negative output terminals, or measure the resistance of the positive and negative excitation terminals, and observe whether it meets the nominal resistance, so as to find the damaged sensor. Finally, when the scale is empty, measure the corresponding output signals of several sensors. If the sensor output value is too small or too large, adjust the diagonal difference in time. After the adjustment, put the weight on the scale and measure the output signals of several sensors again. If the output value of a sensor is too small or too large, it indicates that there is a fault or problem with the sensor here, which needs to be checked and replaced in time.
Common mistakes
Here are some common mistakes people make when using truck scales：
Problem: One of the most common issues with truck scales is inaccurate weighing. This can be caused by several factors, including debris buildup, uneven load distribution, or calibration errors.
Debris Removal: Regularly clean the scale platform to remove any debris, mud, or other foreign objects that might interfere with the weighing process.
Calibration: Ensure that the scale is calibrated regularly according to the manufacturer's guidelines. If the scale is consistently inaccurate, it may require professional recalibration.
Load Distribution: Ensure that the truck is centered on the scale and that the load is evenly distributed.
Problem: Load cells are crucial components that measure the weight placed on the scale. If a load cell malfunctions, it can result in inaccurate readings or complete scale failure.
Inspection: Regularly inspect load cells for signs of wear, corrosion, or damage. Replace any malfunctioning load cells immediately.
Protection: Install protective covers or shields to prevent damage from moisture, chemicals, or debris.
Problem: Truck scales rely on electronic components, and electrical issues such as faulty wiring, power surges, or water damage can cause scale malfunctions.
Wiring Inspection: Regularly inspect all wiring connections for signs of wear, corrosion, or looseness. Tighten or replace faulty connections as needed.
Surge Protection: Install surge protectors to protect electronic components from power surges.
Waterproofing: Ensure that all electronic components are properly sealed to prevent water ingress, which can cause short circuits or corrosion.
Problem: The foundation of a truck scale is critical to its accuracy. Issues such as cracks, settling, or erosion can lead to inaccurate readings.
Foundation Inspection: Regularly inspect the foundation for signs of damage, such as cracks, settling, or erosion. Repair any issues immediately to prevent further damage.
Drainage: Ensure proper drainage around the scale to prevent water from pooling around the foundation, which can cause erosion or settling.
Problem: The indicator is the display unit that shows the weight reading. Malfunctions in the indicator can result in inaccurate readings or failure to display weight.
Check Connections: Ensure that all connections between the indicator and the scale are secure and free of corrosion.
Power Supply: Check the power supply to the indicator. Replace batteries or fix power issues as needed.
Reset: Sometimes, a simple reset of the indicator can resolve minor glitches.
Problem: Over time, the mechanical components of a truck scale, such as the platform, bearings, and joints, can wear out due to constant use.
Regular Lubrication: Lubricate moving parts according to the manufacturer's recommendations to reduce wear and tear.
Component Replacement: Replace worn-out parts, such as bearings or joints, before they fail completely.
After knowing where the fault point of the scale occurs, we still need to find a professional scale maintenance worker from the scale manufacturer to repair it:
Check whether there is any debris on the bottom and around the scale platform, check whether there is a qualified limit gap, check whether the cables are damaged, check whether the instrument components are damaged, whether the junction box is damp, etc. Case: The port truck scale has large data fluctuations and inaccurate weighing. After careful inspection, it was found that the middle position between one end of the scale platform and the foundation was severely squeezed by the ore block. The entire scale platform was completely stuck, and the dustproof rubber was seriously misaligned. The lower position of the scale platform was also accumulated by debris that fell during long-term use, causing serious blockage. At this point, it is necessary to thoroughly remove the debris, use a water gun to clean the debris, and restore the rubber pad. When there is no repeatability problem when using a heavy vehicle for pressure testing, resume use.
Use the voltage range of a 4.5-digit multimeter to measure whether the instrument's working power supply is normal and whether the bridge voltage power supply is normal, and check whether the output signals of each sensor have excessive deviations. In addition, it is necessary to check whether the sensor continuously outputs stable signals. In addition, it is necessary to use the resistance range to check whether the cable is open or short-circuited, and whether the sensor resistance is normal.
If the simple detection method cannot accurately determine the faulty component, the suspected component can be replaced with a good spare part to check whether the fault has been eliminated and determine the fault location and component. It should be noted that when judging certain faults, a sensor simulator can be used to replace the sensor output signal, and the sensor or instrument fault can be determined by checking whether the instrument display is normal.
For those electronic scales where the specific fault location cannot be determined, disconnect the weighing system from other electrical appliances without causing a major impact on production and operation, so as to check whether the weighing system can resume normal operation. For example: in summer, the concrete hopper scale will show drift. When at zero position, it will increase by dozens of kilograms. After many tests, the specific location of the fault cannot be accurately detected. At this time, you can take the method of disconnecting a certain sensor from the junction box wiring in turn for detection. From this, you can find that the temperature of a sensor has serious creep. After replacing this sensor, it can be used normally.
