An oil well pumping unit has a walking beam which raises and lowers a rod connected to a downhole pump. To perform well analysis, it is desirable to know the position of the rod during the stroke. An accelerometer is mounted on the pumping system unit to move in conjunction with the rod. An output signal from the accelerometer is digitized and provided to a portable computer. The computer processes the digitized accelerometer signal to integrate it to first produce a velocity data set and second produce a position data set. Operations are carried out to modify the signal and produce a position trace with stroke markers to indicate positions of the rod during its cyclical operation.