Abstract: A method and device to calibrate an automatic exposure control (AEC) device in an x-ray imaging system is disclosed. An x-ray imaging system has an x-ray generator and tube to generate x-rays, an AEC device to control exposure of the x-rays, and an image sensing system, such as a film/screen combination or a digital recording system, which convert the x-rays into a converted medium, such as light, which can be easily sensed by a sensing medium. To calibrate the AEC device, a detector is placed in the position of the sensing medium to detect the converted medium. The detector detects signals indicative of the x-rays on a sensing medium. Simultaneously, a signal is obtained from the AEC. When the signal from the detector corresponds to a predetermined desired detector output, the output signal from the AEC is stored. The stored AEC output value corresponds to the target AEC output which will produce a proper exposure in the future for the same set of predetermined conditions of the imaging system.