Displacement sensors, also known as linear sensors, are linear devices that use metal induction. Their function is to convert various measured physical quantities into electrical signals. In production processes, displacement measurement is generally divided into two types: measuring physical dimensions and measuring mechanical displacement. Based on the form of the transformation of the measured variable, displacement sensors can be divided into analog and digital types. Analog sensors can be further divided into property-based and structural types. Analog structural types are more commonly used, including potentiometer-type displacement sensors, inductive displacement sensors, synchro sensors, capacitive displacement sensors, eddy current displacement sensors, and Hall effect displacement sensors. A significant advantage of digital displacement sensors is their ability to easily transmit signals directly to computer systems. These sensors are developing rapidly and their applications are becoming increasingly widespread.
The linear displacement sensor works on the same principle as a sliding rheostat, functioning as a voltage divider. It uses a relative output voltage to represent the actual position of the measured location. The following requirements apply to the operation of this device: 1. If the electronic ruler has been used for a long time, and the seals have aged, containing many impurities, and water and oil mixtures severely affect the contact resistance of the brushes, causing the displayed numbers to fluctuate continuously, then the linear displacement sensor's electronic ruler is damaged and needs replacement.
If the power supply capacity is too small, many problems will arise. Therefore, the power supply needs to have sufficient capacity. Insufficient capacity will cause the following issues: the movement of the molten plastic will cause fluctuations in the display of the mold closing electronic ruler, or the movement of the mold closing will cause fluctuations in the display of the injection electronic ruler, resulting in large measurement errors. These problems are more likely to occur if the power supply for the solenoid valve and the power supply for the linear displacement sensor are connected simultaneously. In severe cases, voltage fluctuations can even be measured with a multimeter in voltage mode. If the problem is not caused by high-frequency interference, electrostatic interference, or insufficient neutralization, then it is likely due to insufficient power supply capacity.
Both frequency modulation interference and electrostatic interference can cause the display numbers on the linear displacement sensor's electronic ruler to fluctuate. The signal line of the displacement sensor's electronic ruler must be kept in a separate cable tray from the equipment's high-voltage lines. The electronic ruler must be forcibly grounded, and the ruler's casing must have good contact with the ground. Shielded cables must be used for the signal line, and one end of the cable should be grounded to the shield. With high-frequency interference, a multimeter voltage measurement will usually show normal readings, but the displayed numbers will fluctuate continuously; the same situation occurs with electrostatic interference. To verify if it's electrostatic interference, you can short-circuit the electronic ruler's cover screws with some metal parts on the machine using a power cord. Short-circuiting will immediately eliminate the electrostatic interference. However, eliminating high-frequency interference is difficult using the above method. Frequency converters and robotic arms frequently experience high-frequency interference, so you can try stopping the high-frequency converter or robotic arm to verify if it's high-frequency interference.
If the linear displacement sensor's electronic ruler displays data that jumps regularly at a certain point during operation, or displays no data at all, it is necessary to check whether the insulation of the connecting wire is damaged and whether it is making regular contact with the machine's casing, resulting in a short circuit to ground.
The power supply voltage must be stable. Industrial voltages need to meet a stability requirement of ±[%]. For example, if the reference voltage is 10V, a fluctuation of ± is permissible. Otherwise, it will cause fluctuations in the display. However, if the amplitude of the display fluctuation does not exceed the amplitude of the voltage fluctuation, then the electronic ruler is normal.
The alignment of the linear displacement sensor needs to be excellent, but a parallelism error of ±10° and an angle error of ±12° are permissible. However, if both the parallelism and angle errors are too large, the displayed numbers will fluctuate. In such cases, the parallelism and angle must be adjusted.
During the connection process, extra care must be taken to ensure that the three wires of the electronic ruler are connected correctly, and the power wire and output wire cannot be interchanged. If these wires are connected incorrectly, a large linear error will occur, making it difficult to control and resulting in poor control accuracy. The display will also be prone to fluctuations.
