How to use a multimeter to detect weighing sensors
Weighing sensors are widely used in industrial weighing (such as belt scales, weighing scales, electronic scales, body scales, etc.), force detection, and tension and pressure measurement. During on-site use, the faults of the weighing sensor are generally as follows.
1. Sensor overload, due to unclear communication between the user and the manufacturer, the sensor range does not match the actual force value and weight, resulting in sensor overload and deformation of the sensor bridge arm resistance, causing circuit imbalance. The sensor is not functioning properly, resulting in fluctuations in the output signal and infinite resistance.
2. The sensor lead wire is broken, and the user did not take protective measures during use. The sensor lead wire is usually broken at the sensor lead interface, which affects the use of the sensor without response or sudden changes in measurement values. 3. Improper use of sensors, static sensors can be severely damaged by impact forces, shear forces, torsion, etc., making them irreparable.
So how can we effectively use a multimeter to detect common faults in weighing sensors on site?
1. The sensor manufacturer provides the sensor output sensitivity and power supply voltage at the factory, and we detect the sensor output signal based on these two parameters. The strain gauge weighing force sensor outputs an analog signal in millivolts. For example, the sensor output sensitivity is 2.0mV/V, and the power supply voltage is DC10V. These two parameters can provide us with a linear relationship between the sensor excitation working voltage requiring DC10V and the sensor output signal corresponding to a 2.0mV excitation voltage output for every 1V. For example, if the full range of the sensor is 50KG, then provide the sensor with a DC10V voltage and output 20mV at full range. Based on this relationship, we use a multimeter to measure the sensor output signal in mV range. The no-load output of the sensor is 0mV, which is normal. If it is greater than this value, but close to this value, the numerical change indicates that the sensor has zero drift. If the value is large, it indicates that the sensor is damaged or the internal bridge is a circuit with asymmetric bridge arm resistance.
2. Determine whether the sensor strain gauge is damaged based on the sensor parameters provided by the factory, input resistance, and output resistance. The input and output resistance values of sensors vary from manufacturer to manufacturer. So this needs to be tested according to the manufacturer's labeling. Use a multimeter to measure the resistance of the power supply and power ground, as well as the resistance of the signal line and signal ground. If the resistance value is greater than the factory resistance value, it indicates that the sensor has been overloaded and the strain gauge has deformed. If the resistance value is infinite, the sensor strain gauge is severely damaged and cannot be repaired.
3. Due to frequent wire breakage during the use of the sensor, while the outer layer of the protective wire is intact, we visually inspected the integrity of the sensor wire. We used the ohm range of a multimeter to detect the continuity of the sensor wire. If the resistance is infinite, it is certain to break, and if the resistance changes, the contact is poor.
