Linear displacement sensor working principle and fault handling method - Database & Sql Blog Articles

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Linear displacement sensors operate on a principle similar to that of a sliding rheostat. They function as voltage dividers, converting the physical position of an object into a proportional output voltage. For accurate and stable operation, several factors must be considered:

First, prolonged use can lead to wear and tear of the sensor’s seals, allowing dust, moisture, or oil to accumulate. These contaminants can increase brush contact resistance, causing the displayed value to fluctuate or jump. In such cases, it is likely that the sensor has suffered internal damage and may need replacement.

Second, the power supply must have sufficient capacity. If the power source is too weak, it can cause instability in the sensor readings. This might result in erratic behavior, especially when other high-power devices like solenoid valves are operating simultaneously. Voltage fluctuations may become noticeable, even measurable with a multimeter. If no high-frequency or static interference is present, the issue is likely due to insufficient power supply capacity.

Third, electromagnetic interference (EMI) and static noise can also cause the digital display to flicker or jump. To minimize these issues, signal cables should be separated from high-voltage lines and placed in dedicated conduits. The sensor housing must be properly grounded, and shielded cables should be used for signal transmission. Grounding the shielded Cable at the electrical panel is essential. High-frequency interference often results in normal voltage readings but unstable display values. Static interference behaves similarly. To test for static, briefly connect a metal part of the machine to the sensor cover using a power cord—this should eliminate the interference immediately. However, high-frequency interference requires more advanced troubleshooting, such as temporarily disabling frequency converters or robots.

Fourth, if the sensor displays irregular data during operation, it could indicate damaged insulation or a short circuit caused by contact between the wiring and the machine’s casing. Regular inspection of the wiring is necessary to prevent such issues.

Fifth, the power supply voltage must remain stable. Industrial applications typically require a stability of ±0.1%. For example, if the reference voltage is 10V, a fluctuation of ±0.01V is acceptable. Any larger variation can lead to display instability. However, if the display fluctuation does not exceed the actual voltage change, the sensor is likely functioning correctly.

Sixth, proper alignment of the linear displacement sensor is crucial. While some tolerance is allowed—±0.5mm for parallelism and ±12° for angular alignment—excessive misalignment can cause digital jitter. If this occurs, realignment is necessary to restore accurate performance.

Finally, during installation, care must be taken to ensure correct wiring. The three wires of the sensor—power, ground, and output—must be connected properly. Incorrect connections can lead to significant linearity errors, poor control accuracy, and frequent display fluctuations. Always double-check the wiring before commissioning the system.