"How to accurately measure OD and ID of a circular part using VMeasurement in B&R mapp Vision?"

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Hello,

I am currently using the VMeasurement Function Block in B&R mapp Vision to measure the outer diameter (OD) and inner diameter (ID) of a circular part (washer).

My current approach is to use Edge Model Mode to detect edge points on the outer and inner contours, and then calculate the diameter using the distance_cog operation.

However, as shown in the attached image, the detected edge points are not always located at the positions I expect. As a result, the measured OD and ID values contain errors and are not consistent.

Current Configuration

  • Function: VMeasurement

  • Model Type: Edge Model Mode

  • Measurement Method: Edge point detection followed by distance_cog

  • Target: Outer diameter (OD), inner diameter (ID), and thickness of a washer

Issue

  • The detected edge points are not located exactly opposite each other with respect to the circle center.

  • Measurement results vary depending on the detected edge locations.

  • It is difficult to obtain stable and accurate diameter measurements.

Questions

  1. Is there a recommended way to accurately measure the OD and ID of a circular part using only VMeasurement?

  2. What Function Blocks or measurement methods are commonly used for OD/ID measurement of circular parts in mapp Vision?

  3. Is there a better approach than Edge Model Mode, such as circle fitting or blob-based measurement?

  4. What is the recommended method for achieving subpixel-level accuracy when measuring OD and ID?

I have attached screenshots of my current configuration and measurement results for reference.

Any advice or best practices would be greatly appreciated.

Thank you.

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