Measurement Using Grating Ruler
The fundamental principle involves installing two fixed-length grating rulers on the outer sides of both ends of the longitudinally welded steel pipe. The rulers are driven by rods positioned near the pipe ends, and the length of the pipe is measured through optical interference phenomena.
This method boasts high accuracy. However, grating rulers are expensive and difficult to maintain, making them sensitive to dust and on-site vibrations.
Camera-Based Length Measurement
Camera length measurement utilizes image processing to determine the length of the steel pipe. It involves installing a series of equally spaced photoelectric switches on one section of the conveyor rollers for the longitudinally welded steel pipe, and adding a light source and camera to the other section. As the pipe passes through this area, the length is determined by the position of the image captured by the camera on the screen, relative to the photoelectric switches.
A key feature is its ability to perform online measurements and obtain length data when the pipe passes through the measurement area without interruption.
Encoder-Based Length Measurement
This method involves installing an encoder on a cylinder, which drives the steel pipe along rollers. A series of equally spaced photoelectric switches are installed on the opposite side. When the pipe touches the photoelectric switch at the end of the cylinder, the cylinder's stroke can be converted from the recorded encoder readings to calculate the pipe's length.
A notable characteristic is that the pipe needs to be lifted for measurement. Additionally, there may be some errors in photoelectric switch detection, requiring thorough measurements.
Improved Encoder-Based Length Measurement
This is an indirect measurement method that determines the length of the steel pipe by measuring the distances between its ends and respective reference points. A length measuring car is set up at both ends of the pipe, with an initial position of zero and a spacing of L. Then, the encoder measures the travel distance (L2, L3) of the car to one end of each pipe, thereby indirectly obtaining the pipe's length.
This measurement method overcomes difficulties such as the pipe's large size, complex production site environments, and the inability of measurement mechanisms to span under the pipe supports. It offers convenient operation, with a measurement accuracy of less than ±10 mm and a repeatability accuracy of ≤5 mm.
