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T
Tobias Nagel
Visitor II
August 16, 2017
Question

Measuring VL6180X with close distances

  • August 16, 2017
  • 1 reply
  • 739 views
Posted on August 16, 2017 at 16:36

Hey,

I am having the VL6180X Satellites sensor for ranging measurements. After connecting it, I receive some measurement values - but they are the wrong ones. The sensor isn't reacting to changes in a distance between 0mm and ~50mm. It keeps showing me the value '4 mm'. Beyond that distance of 50 mm, the values start increasing, which is fine.

Is there anything I am forgetting? I have set the Offset to 0 mm. The range-ignore features and the early convergence are disabled (by register 0x02D). I performed the measurements in the darkness.

Thanks in advance!

#close-measurement #vl6180x
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    1 reply

    J
    John E KVAM
    ST Employee
    January 2, 2018
    Posted on January 02, 2018 at 17:45

    At close distances the VL53L0 has a bit of a blind spot. The light from the laser hits bounces between the target and the material the sensor is mounted on. This 'multipath' means the reported distance starts increasing as the target gets very close. If you can guarantee the actual distance never gets closer than 1.5cm, the result is accurate. But below 1.5cm there is an issue.

    Our solution is to back the sensor up in some sort of cavity to guarantee the real target cannot get too close.

    - john

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