It is suggested that position‐sensitive detectors may be used to observe the time history of sample motion, such as that which takes place when impulse is imparted to a material sample during blowoff. In this application a laser beam is reflected from the rear surface of the sample or from a mirror attached to the sample, and the detector reproduces the time history of the position of the reflection. In this work the response of this type of detector to a rapidly moving laser beam has been studied. It has been found that detectors selected from those presently available can reliably locate the centroid of a laser beam that moves at least as fast as 0.19 cm/&mgr;sec. It is suggested that a reasonable criterion for determining the maximum velocity with which a detector may be used is &ngr;≤&Dgr;X/0.5RdC, where &Dgr;Xis the desired position resolution andRdandCare the distributed resistance and capacitance of the detector, respectively.