Analysis of the reasons for the small range accuracy and large range inaccuracy of weighing equipment
In industrial production, commercial trade, and scientific research experiments, the accuracy of weighing equipment is directly tied to data reliability and business stability. However, in practical applications, the phenomenon of "precise weighing at small ranges but significant errors at large ranges" is common — this issue is not accidental, but the result of multiple factors (including the equipment’s mechanical structure, core component performance, and circuit system stability) acting together. This article will systematically analyze the causes of this problem and provide targeted solutions and preventive measures to help users quickly troubleshoot and ensure the stable operation of weighing equipment.
The weighing logic of weighing equipment follows the chain: external force → mechanical structure transmission → sensor signal conversion → circuit processing → data display. Inaccurate weighing at large ranges essentially means one link fails to operate stably under "high-load" conditions. Specifically, there are four main categories of causes:
The mechanical structure is the "skeleton" of weighing equipment. At small ranges, the load pressure is low, so structural deformation is negligible; at large ranges, the load exceeds the structure’s tolerance threshold, leading to irreversible deformation or component misalignment — directly causing weighing errors.
- Insufficient Rigidity of the Weighing Platform/Support Frame
If the weighing platform uses thin steel plates, low-quality alloys, or the support frame is designed without considering "bending resistance" (e.g., overly wide support spacing, undersized beam cross-section):
- At small ranges, the structure only undergoes minor elastic deformation, which has little impact on weighing results;
- At large ranges, the weighing platform will sag significantly or the support frame will tilt, preventing the load from being evenly transmitted to the sensor. Part of the pressure is "absorbed" by structural deformation, so the displayed value ends up smaller than the actual weight.
For example: If the thickness of a commercial electronic platform scale’s weighing platform is reduced from 3mm to 1.5mm, the error is only 0.1kg at a 50kg small range, but expands to 1–2kg at a 200kg large range.
- Loose or Worn Connectors
Weighing platforms are usually fixed to sensors, and support frames to bases, via bolts, gaskets, etc.:
- At small ranges, the tension/pressure on connectors is low, so no displacement occurs;
- At large ranges, if connectors are loose (e.g., bolts not tightened) or worn (e.g., gaskets cracked), the weighing platform will experience "offset deformation" — some areas sink while others are suspended. The sensor cannot receive uniform pressure signals, resulting in weighing errors.
- Over-Constrained Limiting Devices
To prevent sensor damage from vibration or overload, most equipment is equipped with limiting devices (e.g., upper/lower limit posts, transverse limit blocks) to restrict the weighing platform to small vertical movements:
- At small ranges, there is a tiny gap between the limiting device and the weighing platform, so no constraint occurs;
- At large ranges, if the limiting device is installed too tightly (gap < 0.5mm), the weighing platform will make rigid contact with the device when pressed down. The limiting device then exerts a "support force" in reverse, offsetting part of the actual load — causing the displayed weight to be smaller than the actual weight, with the error increasing as the load grows.
The sensor is the "heart" of weighing equipment, responsible for converting mechanical pressure into electrical signals. Its range compatibility, linearity, and aging degree directly affect weighing accuracy. The phenomenon of "precise at small ranges but inaccurate at large ranges" is mostly related to the sensor’s range mismatch, linearity failure, or overload damage.
- Sensor Range Underselection
A sensor’s range must match the equipment’s maximum capacity (typically requiring sensor range ≥ equipment max capacity × 1.2). If the range is underselected (e.g., a 200kg-capacity device uses a 150kg-range sensor):
- At small ranges (e.g., ≤50kg), the sensor operates in its "linear working interval," with output signals proportional to the load — ensuring accurate weighing;
- At large ranges (e.g., ≥100kg), the sensor exceeds the linear interval and enters the "saturation zone" — signal growth slows or stagnates as the load increases, so the displayed weight is consistently lower than the actual value and fails to rise normally.
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