## 2 Materials and Methods
Figure 2: Design of an automatic control measuring system for the 6 m wide HDPE/LDPE polymer geomembrane. 1—frame; 2—support roller; 3—laser sensor; 4—carriage; 5—stepper motor; 6—control unit; 7.8—switches; 9—moving geomembrane; 10—rotation angle sensor. 2. On carriage 4, drive motor 5 is connected to electronic control unit 6, which is also connected to laser sensor 3. The inputs of the electronic control unit 6 are connected with limit switches 7 and 8, fixed at the ends of the trajectory of movement of carriage 4. Moving geomembrane 9 rests on rotating support roller 2. The angle of rotation of rotating support roller 2 relative to the beam of laser sensor 3 is measured using angle sensor 10, which is connected to electronic control unit 6. The developed system works as follows. Before starting to measure the thickness of moving polymer geomembrane 9, the entire surface of support roller 2 is pre-scanned by laser sensor 3 by means of moving carriage 4 with laser sensor 3 between limit switches 7 and 8 and rotation of support roller 2. The obtained value of the distance A is stored in electronic unit 6. The microrelief of the of the rotating support roller 2 violations are fixed in two coordinates. The first coordinate is calculated by the number of control pulses arriving at drive motor 5 from electronic control unit 6. The second coordinate is calculated from the information from rotation angle sensor 10. Regardless of the speed of movement of polymer geomembrane 9, electronic control unit 6 takes into account violations of the microrelief of the friction surface of rotating reference roller 2. As a result, in the non-volatile memory of control unit 6, the value of the distance from laser sensor 3 to the friction surface of rotating support roller 2 is stored, that is, its microrelief with reference to geometric dimensions and position. In the operating mode, when geomembrane 9 is introduced into the measurement zone, its tight fit to the friction surface of support roller 2 is achieved, and the value of film 9 thickness is recorded on the indicator of electronic control unit 6. Scanning is carried out within the normalized width of the geomembrane, since, due to the uneven edges, after controlling its thickness, the edges of the geomembrane are cut off. The thickness of the geomembrane T is calculated as the difference between the distance A, which is in the memory of electronic control unit 6, and the distance B, measured by laser sensor 3, to the surface of geomembrane 9 in real-time during the movement of geomembrane 9. The measurement error depends on the parameters of the laser sensor used and the mechanical rigidity of frame 1. Laser sensor 3 is rigidly attached to carriage 4, which is moving along frame 1; therefore, the distance from sensor 3 to the friction surface of rotating support roller 2 is a known value, taking into account its microrelief. Electronic control unit 6 provides power and receives the information from limit switches 7 and 8, rotation angle sensor 10, laser sensor 3, and control drive motor 5; it provides a prompt indication of the film thickness value, fixing the change in the geomembrane thickness, the geometric position of the place of violation, as well as real-time detection of thickness violations and sound and light indication of violation detection to attract the attention of maintenance personnel. The blocks of the device for measuring the thickness of a moving wide polymer geomembrane are made based on known technical solutions as follows. Frame 1 is made in the form of an aluminum profile AlMgSi, alloy AD-31, with a size of 60 \(\times\) 60 mm, so that the entire structure has maximum rigidity. Support roller 2 is made in the form of a freely rotating steel roller supported on roller bearings. Laser sensor 3 is made using a commercially available analog-to-digital laser sensor of the LE250 IQ type. Movable carriage 4 is made in the form of a platform with 4 wheels and a drive motor.