Cable elongation measurement process:

1. Take the wire to be tested with length L and diameter D, fix the two ends of the wire to the support column and the digital display tension measuring device respectively, turn the fine adjusting knob, and move the moving mirror end and the digital explicit tension measuring instrument.

2. To ensure that the wire under test is in an elongated state.Then adjust the light path so that the ring center of the interference ring appears at the center of the glass observation screen. If the center of the ring of the interference ring is not at the center of the glazed glass viewing screen, adjust the mirror to ensure that the center of the interference ring is at the center of the viewing screen of the ground glass.

3. By rotating the fine adjusting knob, the fringe of the interference ring observed on the wool glass observation screen is sparse and the brightness is suitable, so that the number of the interference rings can be conveniently recorded, Turn on the digital tension tester and set zero,   then rotate the fine-tuning knob,and the digital tension tester will stretch the wire to be tested,When there is a reading on the digital display tension tester and the phenomenon of "gushing out" or "falling into" the interference ring appears on the observation screen of the ground glass,the automatic counter of the interference ring at the rear of the glass observation screen automatically records the number of stripes N,The digital display tension tester can record the tensile force F of the wire to be measured after changing N stripes.The elongation of the wire under test is equal to the displacement of the moving mirror, which is equal to the change of the light path difference of two light rays in the optical path.Thus, the Young's modulus of the wire to be tested can be obtained.

4. After measuring the number of fringes N and tension F, the experimenter can calculate them by himself.He can also connect the digital explicit tension measuring instrument and the interference ring automatic counter to the computer through the data line, and the measured results can be transmitted directly to the computer.The calculation is carried out automatically by the computer according to the above formula.