How to adjust the positioning of a fiber optic sensor

Adjusting a fiber optic positioning sensor involves proper alignment, sensitivity calibration, and setting reference points to ensure accurate position detection.

Understanding the Sensor

A fiber optic position sensor measures object position by detecting changes in light reflected from a target along the fiber. Key components include the optical fiber, light source (LED or laser diode), reflector, and light detector. Movement of the reflector modulates the light, which is then processed to determine displacement or position .

Basic Adjustment Steps

1. Mount the Sensor and Target Properly
   • Secure the sensor tip perpendicular to the target surface.
   • Ensure the fiber optic cable is supported to avoid strain on the probe .
   • Use a stable base, such as a granite plate, for high-precision applications.
2. Set Reference Points
   • Use the sensor's Preset or SET functions to define zero and full-scale positions.
   • For Keyence sensors, press the SET button while the object is at the reference position to set the baseline, and adjust the second point to define the full-scale range .
   • This ensures the sensor accurately maps the physical movement to the output signal.
3. Adjust Sensitivity
   • Fine-tune the sensor's sensitivity to account for variations in light intensity caused by dust, dirt, or target reflectivity.
   • Some sensors allow automatic sensitivity adjustment while the workpiece passes through, which is useful for continuous operations .
   • Manual adjustments can be made using the MODE and SET buttons to achieve the desired detection threshold.
4. Select Output Mode
   • Choose between Light-ON (L-on) or Dark-ON (D-on) modes depending on whether the sensor should trigger when light is detected or blocked .
   • Confirm the output response matches your application requirements.
5. Lock Settings
   • Once adjustments are complete, lock the sensor settings to prevent accidental changes.
   • On Keyence models, holding the MODE button along with other designated buttons can enable or disable button operation .

Advanced Calibration (Optional)

For high-precision applications:

• Use linear positioning stages (ball bearing, crossed-roller, or air bearing) to move the target in controlled increments.
• Record sensor output at each position and create a calibration curve to correct for non-linearities .
• Ensure temperature stability and proper handling to maintain micron-level accuracy.

Tips for Reliable Operation

• Keep the optical path clean and free from obstructions.
• Avoid bending the fiber sharply to prevent signal loss.
• Periodically check calibration, especially if the sensor or target is moved.
• Use a specular or diffusive reflector appropriate for your sensor type to maximize signal quality . By following these steps, you can ensure your fiber optic positioning sensor is accurately adjusted for precise measurement and reliable operation.