A double crystal x‐ray monochromator system has been developed for use on synchrotron radiation sources. The system consists of two separate Bragg reflecting crystals constrained by a mechanical linkage system enabling it to tune continuously in x‐ray energy, always maintaining an exit beam of constant offset and direction relative to the incident beam. Accurate parallelism between the two crystals is maintained by a piezoelectrically‐controlled analog feedback circuit.