DS EN 12543-5:1999 Non-Destructive Testing - Characteristics Of Focal Spot In Industrial X-Ray Systems For Use In Non-Destructive Testing - Part 5: Measurement Of The Effective Focal Spot Size Of Mini And Micro Focus X-Ray Tubes Defines a method for the measurement of focal spot dimensions within the range of 5[mu]m to 300[mu]m of X-ray systems up to and including 225 kV tube voltage, by means of radiographs of sharp edges.