Cordin Pin Oscillograph
Earl Pound, a professor at the University of Utah, and Bill Partridge formed the Cordin Company in 1956 to build high-speed cameras, initially for explosives manufacturing.
The pin oscillograph technique [used in the measurement of detonation velocities] shows the time of arrival of an ionized shock wave at discrete pin stations along the length of an explosive charge. The distance between pin switches, and the time required for the wave to travel between them is known, thus the detonation velocity can be readily calculated. Increased accuracy in the measurement is achieved by taking an average velocity from a number of pin stations along the charge length.
The components of the pin oscillograph consist of a triangular wave generator, a crystal controlled marker generator, a pulse forming circuit and a modified Tektronix 535 oscilloscope.
The triangular wave generator lengthens the recorded trace from a straight line to a zig-zag sweep to obtain sufficient time resolution for a reasonable accuracy in the determination of velocity. The crystal controlled marker generator superimposes time markers on the trace to facilitate reading of the records. The pulse forming or mixer circuit is a network of resistors, capacitors and diodes which form and send to the oscillograph electrical pulses indicating the arrival of the detonation wave at the various pin stations along the explosive charge.
Ignition time lag: a measure of explosive energy release (Rydlund 1964):
The pin oscillograph relies principally on the heavy degree of ionization found in a chemical reaction zone. The arrival of the reaction zone at several discrete locations along a charge column or pin stations is recorded chronographically. When the arrival times are applied to the measured distances between the pins, finite velocities can be determined. The velocities are usually averaged to find an overall, or effective, detonation velocity.
The equipment consists basically of a modified oscilloscope and triangular wave generator, which lengthens the straight line sweep of the scope to a zig~zag trace in order to obtain sufficient time resolution, a crystal controlled marker-generator that superimposes time markers on the trace to facilitate reading of the records, and a pulse-forming circuit that imposes an electrical pulse upon the sweep when the pins indicate the arrival of the reaction zone. A Polaroid camera attached to the scope records the zig-zag sweep complete with time markers and pulses for analyzing.