Patent ID: 7500959

Claim:
A method of configuring motorized injection device having a piston rod that pushes a piston in a medication cartridge to expel medication from the cartridge and having an actuator that drives the piston rod, the method comprising the steps of: a. calculating a relationship between movement of the actuator and expected movement of the piston rod; b. moving the actuator an amount expected to move the piston rod a predetermined distance; c. measuring the actual distance the piston rod moves when the actuator is moved in step b; d. determining the error between actual movement of the piston rod and expected movement when the actuator is moved a predetermined distance, wherein expected movement is a value calculated from design specifications and actual movement is a value measured from a calibration procedure; e. programming a processor to control the actuator to compensate for the error of step d so that the piston rod is moved by a desired amount even though the actuator is moved by a greater or lesser amount than would be expected to move the piston rod by the desired amount.