Main characteristic parameters of the displacement sensor

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As sensor applications continue to grow across various industries, the demand for high-quality and reliable sensors is also increasing. This is especially true for displacement sensors, which are crucial in precise measurement tasks such as motion detection. For engineers and researchers working on R&D projects involving displacement sensors, it's essential to understand not only how they work but also the key considerations when using them. Before diving into their usage, let’s first take a closer look at the main technical parameters of a linear displacement sensor.

Main Technical Parameters of Displacement Sensors

Nominal Resistance: This refers to the resistance value marked on the potentiometer. It serves as a reference point for evaluating performance.

Allowable Error: This represents the percentage deviation between the actual resistance and the nominal resistance. A smaller allowable error means higher accuracy. Typically, this value ranges from ±10% to ±20%, depending on the application.

Linear Accuracy: Also known as linearity error, this parameter measures how closely the sensor output matches an ideal straight line. The lower the value, the better the performance.

Life Span: Conductive plastic displacement sensors can last over 2 million cycles, making them suitable for long-term use in industrial environments.

Repeatability: This indicates the sensor's ability to return the same output under identical conditions. A smaller repeatability error means more consistent results.

Resolution: The smallest displacement that the sensor can detect. Higher resolution means greater sensitivity, and conductive plastic sensors offer extremely fine resolution.

How to Use a Displacement Sensor

Displacement sensors typically operate by applying a voltage and measuring the corresponding output voltage or resistance change. Let’s take two common types—linear and magnetostrictive displacement sensors—as examples to explore their practical usage.

(1) Using a Linear Displacement Sensor

American TOM Company produces precision linear displacement sensors with a long continuous conduction track. These are ideal for absolute position sensing in control and measurement systems. Their linear accuracy is as high as 0.05%, making them suitable for high-precision applications like gantry hydraulic presses.

In a hydraulic press system, different models such as the Kl lower slide type and KTC pull rod type are installed on the main cylinder and hydraulic pad. During semi-automatic operation, these sensors move along with the mechanical parts, sending analog signals to the FX2N-8AD module. The module then converts the signal into digital data for the PLC to process. The effective measurement range for the main cylinder is 500 mm, and for the hydraulic pad, it is 400 mm.

(2) Precautions When Using a Magnetostrictive Displacement Sensor

Magnetostrictive displacement sensors measure the absolute position of a moving magnet without physical contact, offering high precision and reliability. They are widely used in real-world applications such as liquid level monitoring and position tracking.

When installing these sensors, several factors must be considered. First, ensure that the assembly parts meet the specified tolerance requirements. Second, if the hydraulic cylinder is made of ferromagnetic material, a non-magnetic spacer should be placed beneath the sliding magnet ring. All screws securing the fixed magnets must also be non-magnetic to avoid interference.

Additionally, it's important to place the area requiring measurement within the sensor's effective working range. Due to design limitations, there may be dead zones at both ends of the sensor's range. For example, for a 5-meter measurement range, the dead zone at the front end is approximately 63.5 mm. For a 7.6-meter range, the dead zone increases to about 66 mm.

Conclusion

As the market for displacement sensors continues to expand, so do the expectations for performance and reliability. For engineers and developers, understanding the principles, parameters, and proper usage of these sensors is fundamental. This article has provided an overview of the key technical features, practical applications, and important considerations for both linear and magnetostrictive displacement sensors. With this knowledge, users can make informed decisions and optimize sensor performance in their specific applications.