In the material quantitative packaging process of industrial production, the container bag packaging scale plays a crucial role in measuring the weight of the materials and ensuring the accuracy of filling. Among them, the sensor, as the key component that collects weight signals and converts them into electrical signals, its working condition directly determines the operational efficiency of the entire machine. Due to long-term exposure to mechanical stress and environmental erosion, sensors are prone to various abnormalities. When the equipment shows the following signs, it usually indicates that the sensor may have been damaged or its performance has declined, and timely inspection and replacement are required.
1. Unexpected deviations occurred in the weighing data.
After being calibrated, a normal packaging scale should maintain high stability. If there is a significant fluctuation in the weight of the finished product after filling, or if the overall weight continuously shifts in one direction (towards being heavier or lighter), this is usually the first sign that there is a problem with the sensing element.
• Increase in repeatability error: For the same set target weight, the results of multiple fillings show significant differences, and the data dispersion exceeds the normal allowable range.
• Frequent reading fluctuations: During static placement or low-speed feeding processes, the weight values displayed by the instrument are unstable, experiencing irregular and intense up-and-down fluctuations, making it difficult for the control system to accurately determine the timing for cutting off.
II. Abnormal Behaviors in the On-Boarding or Idle State
The sensor not only bears the load but also senses the weight of the packaging bag itself (the bag's own weight). After ruling out mechanical jams or air source issues, the following empty-load abnormalities typically point to a fault in the sensing system:
• Peel function failure: After performing the peeling operation, the display cannot return to zero, or it becomes extremely unstable after returning to zero. Even a slight vibration causes the value to drift.
• Negative overload alarm: When no materials or packaging bags are placed, the system alerts that the weight exceeds the lower limit or displays an incorrect negative value. This is usually due to a significant drift in the sensor's zero point.
III. Nonlinear Distortion in Signal Output
Although end users usually do not directly access the analog signals of the sensors, they can indirectly determine the situation through feedback from the upper computer or weighing instrument:
• Decrease in linearity: During multiple-point testing across the entire range, it was found that the proportional relationship between the actual weight and the sensor output signal no longer followed a linear pattern. The error was particularly significant in the middle range of the full scale.
• The lag phenomenon has intensified: When loading and unloading materials of the same weight, the return error of the sensor increases, manifesting as "the weight exceeds the limit when feeding stops, and the weight drops too much after unloading".
IV. Indications of Combined Damage to Mechanical Interconnected Components
The sensors are usually connected to the load-bearing support through an elastic body structure. When troubleshooting, it is also necessary to pay attention to the following physical manifestations of damage:
• Loose or deformed fasteners: Check if there are any signs of loosening of the fixing bolts on the sensor mounting base, or if the force-bearing steel balls protecting the pressure head have any signs of wear or jamming.
• Damage to cables and connectors: Check if the shielding cable of the sensor has any marks indicating being squeezed or pulled by heavy objects. Also, observe if the connectors inside the junction box have been affected by moisture and oxidation or if the terminals are loose. Such damages can cause signal transmission distortion, resulting in symptoms similar to sensor failure.
V. Hidden Degradation of Electrical Characteristics
When the equipment is powered off, the resistance setting of the multimeter can be used to conduct a simple measurement of the input/output terminals of the sensor. If a significant deviation is observed in the bridge arm resistance value, or if there is an unstable short circuit or open circuit at the excitation voltage input terminal, it indicates that the strain gauge inside the sensor may have undergone irreversible deformation or damage.
If the sensing system of the packaging scale malfunctions, it will not only reduce production efficiency but also lead to serious material waste or an increase in packaging defect rates. Operators should conduct regular inspections of the weighing system. Once any signs of data drift, unstable signals, or mechanical joint damage are detected, the machine should be stopped immediately for maintenance to avoid small mistakes resulting in major losses. During daily maintenance, keeping the surrounding environment of the sensor clean and preventing corrosive dust from entering the junction box are effective measures to ensure its long-term stable operation.
