At present, the maintenance of common problems of electronic scale sensors in China is based on the principle that most of the resistance strain type load cells are used. The application of electronic scales is more and more common. The electronic scales have the advantages of fast weighing, intuitive display and easy wear and tear, and have gradually replaced mechanical scales. The electronic scale mainly consists of a load-bearing force transmission system, a load cell and a display instrument. The working principle of the commonly used resistance strain type load cell is that the elastic body is elastically deformed under the action of external force, so that the resistance strain gauge attached to the surface thereof is also deformed together, and the resistance value of the strain gauge changes after the resistance strain gauge is deformed. Since the strain gauges are connected in a balanced bridge type, the change in the resistance value of the strain gauge causes the bridge to be unbalanced, and the signal is output from the surface, thus completing the process of converting the external force into a signal.
There are several phenomena in the electronic scale, and it is suspected that the load cell is faulty:
(1) The electronic scale does not display zero, and the display keeps flashing.
(2) After the electronic scale displays zero, the weight is added and the weighing number is not displayed.
(3) The weighing of the electronic scale is not accurate, and the displayed weighing number is inconsistent with the number of added weights.
(4) The repeatability of the electronic scale is not good, and the same weight is added, sometimes the weighing is accurate, and sometimes the weighing is not accurate.
(5) When the electronic scale is unloaded or loaded, the displayed number is unstable, drifting or jumping.
These phenomena may all be failures of the load cell. If you can accurately determine that the fault is in the sensor, this will greatly improve the work efficiency and speed up the repair of the electronic scale. The sensor to be judged is separately removed from the system, and the input impedance and the output impedance are measured separately. The input impedance is 380Ω and the output impedance is 350Ω. If the measured data is not within this range, the sensor is damaged. If the input impedance and output impedance are open, you can check whether the sensor signal cable is disconnected. When the signal cable is intact, the sensor strain gauge is burned, usually because of a large current entering the sensor. When the measured input impedance and the output impedance are unstable, the signal line insulation may be broken, the insulation performance may be degraded, or the sensor may be wetted, so that the bridge is not well insulated from the elastomer. The zero output signal value of the sensor is generally between (-3mv and 2mv). If it is far beyond this standard range, it may be that the sensor is overloaded and the elastomer is plastically deformed, making the sensor unusable. If there is no zero signal or the zero output signal is small, it may be caused by the strain gauge in the load cell being detached from the elastic body or supported by the scale body.
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Tag: load cell sensor signal electronic scale FAQ strain gauge
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