Automatic tensioning device and rope length measurement device

The invention discloses an automatic tensioning device and a rope length measurement device and relates to the technical field of engineering machines. The technical problem that a meshing gap between a worm wheel and a worm in the prior art is large, so that a measurement error is large is solved. The automatic tensioning device comprises a to-be-tensioned component connecting seat, an elastic device, a movable connecting mechanism and a fixing seat body. The to-be-tensioned component connecting seat can be moved to a preset position from an initial position relative to the fixing seat body. The elastic device is arranged between the to-be-tensioned component connecting seat and the fixing seat body and elastic force exerted to the to-be-tensioned component connecting seat by the elastic device can move the to-be-tensioned component connecting seat to the preset position from the initial position. The rope length measurement device comprises a reel, a worm wheel, a worm, a rotating potentiometer, a shell and the automatic tensioning device and is used for reducing measurement errors of the length of a steel wire rope.