The ballistic pendulum is used to measure the impulse imparted to the plates as a result of a blast load. It consists of a steel I-beam suspended from the roof by four spring steel wires. The spring steel wires have adjustable screws attached to them, enabling the pendulum to be levelled. At either end of the pendulum the test specimen (experimental rig) and balancing masses are attached. The balancing masses are used to balance the pendulum to ensure that the spring steel wires carry approximately the same weight thus ensuring that the impulse acts through the centroid of the pendulum. Also attached to the ballistic pendulum is a recorder pen. This pen is used to record the oscillation amplitude of the pendulum onto a sheet of tracing paper. The oscillation amplitude relates directly to the impulse imparted onto the test specimen.