Details are given of an item of purpose-built hardware which has been integrated into an automatic data collection system for an x-ray diffractometer. The complete system enables both the investigation time and the volume of data collected to be reduced but does not affect the overall reproductibility. Although the use of the device is described with reference to the collection of x-ray diffraction data it is considered likely that the device could be applied to the collection of any similar types of data where a scanning procedure is involved.