According to the technological requirements of different manufacturers, precision tubes length measurement systems with a variety of length measurement methods. There are the following:
1, The grating length measurement
The basic principle is: the outer ends of precision tubes are provided two fixed length of the grating, the use of rodless cylinder driven grating near precision tubes ends, using light interference to achieve precise measurement of the length of the tube.
It is characterized by high accuracy. But the scale is expensive and difficult to maintain, the impact of dust and vibration is very sensitive site.

2, The camera length measurement.
Camera length measurement is the use of image processing to achieve precision tubes length measurement, the principle is equidistant series of photoelectric switches installed in the precision roller conveyor tube a certain period, the increase in light and camera on the other section. When precision tubes through this region may be determined by the precision tube length cameras capture an image on the screen at a position based on a photoelectric switch.
Features are available for online measurement, precision tubes can be obtained by measuring the length of the data when long area, no interval. Shortage is: If you do not ad hoc light source, precision tubes will be subject to interference outside light, but after using the light due to the ad hoc precision tubes after chamfered tube end while the high brightness light reflection is very strong, is likely to cause reading errors.

3, The encoder measuring length
The principle is to install the encoder in the cylinder at the cylinder to promote the use of precision tubes in rollers movement on the other side of the mounting equidistant series of photoelectric switches, precision tubes is met when the photoelectric switch cylinders push the tube end, from the recording encoding readings, converted the stroke of cylinder, so you can calculate the length of the precision tubes.
Characterized by the need to raise precision tubes measuring length. In addition, there are certain photoelectric switch detects an error, you may need to be fully measured.

4, Improved length measuring encoder
This method is an indirect measurement, by measuring the distance between two end precision tubes with the respective reference point indirectly measured precision tube length. In the precision tubes both ends of the measuring station set up a long car, the initial position is zero position, spacing L. Then move the editor precision tube length to each end of the distance traveled (L2, L3), L-L2-L3, is the length of the precision tubes.