Measurement method, calibration device and method of iron roughneck screwing-on and screwing-off torquemeter

The invention discloses a measuring method, a calibration device and a calibration method of an iron roughneck screwing-on and screwing-off torque measuring instrument. The calibration device comprises a rack and a loading device, the rack is provided with two clamping frames which are oppositely arranged, and the two clamping frames are used for clamping a main shaft of a measuring instrument inside; a center hole is formed in the midpoint position of the loading force arm, one side of the loading force arm is fixedly connected with one end of the measuring instrument main shaft through the center hole, the other side of the loading force arm is rotationally connected with one clamping frame through the center hole, and the two ends of the loading force arm can rotate around the center line of the center hole of the loading force arm; the other end of the measuring instrument main shaft is fixedly connected with the other clamping frame; the two ends of the loading force arm are connected with force applicat