Range And Accuracy; Error Modes; Optimal Measurement Range Of - Parallax 28044 User Manual

A total of 5,120 bytes of binary data is sent. An ASCII footer ("END") is attached to the end of the binary
data stream to assist in identifying the end of frame.
This command can be used from within the LRF Image Viewer tool to easily view the image.
Terminal Example:
:P
<binary data>END
:

Range and Accuracy

The LRF Module is most accurate within its optimal measurement range of 6–48 inches (15–122 cm).
Within this range, error can span from zero (no difference between actual distance and the distance
calculated by the LRF) to 5%. On average, the error is approximately 3%.
Within the optimal measurement range, the horizontal position of the laser spot within the camera's
frame (which is used to determine distance to the target object) changes noticeably. At longer distances,
although the camera can still "see" the laser spot, the horizontal position does not change as much,
causing a significant reduction in accuracy. Accuracy also varies with lighting conditions and material of
the target object, which affect the LRF Module's capability to determine the laser spot within the camera's
frame.
The LRF Module intentionally limits the maximum detectable distance to 100 inches (254 cm). At
distances less than 6 inches, the laser spot is out of the camera's field-of-view, so no range calculation
can occur. See Optical Triangulation, page 17, for more details.
The following chart shows example measurements taken with a LRF Module. The Calculated Distance,
Difference (Δ), and % Error will vary slightly per unit.

Error Modes

In the event that the LRF enters the error state (signified by a blinking orange LED status indicator), an
ASCII message identifying the failed operation will be transmitted on the SOUT (Serial Out) pin.
Messages include:

ERR: cam.start. Error initializing the camera on LRF power-up. This may be caused by a
communication error between the Propeller and camera.

ERR: cam.init. Error performing the "S" command (Reset camera to initial settings). This may
be caused by a communication error between the Propeller and camera.
Copyright © Parallax Inc. Parallax Laser Range Finder (#28044) v2.0 10/31/2015 Page 10 of 23