The time differences of a simultaneous initiation device including the initiation time differences of the detonators, build-up time differences of the detonation waves of the boosters and finally the main charge can be measured by the distances of the Dautriche line grooves imprinted in a target block-mild steel disc-by the intersection of detonation waves. Accuracy time differences of better than 0.1 μs can be achieved by carefully arranging the test set-up.