The Application
Needing to provide feedback to pilots during training, a military-based company developed an approach to gauge how well pilots-in-training were firing their aircraft’s weaponry. The pilots would fly over a test area strafing an appointed target. As they fired, microphones near the targets helped to "score" the hits by digitally recording the shock waves as the projectiles struck the target. This data was then analyzed, providing statistics on bullet speed and strike location immediately. Originally, this military branch used a system that was composed of expensive, custom components which made it difficult and costly to replace old components, or expand existing systems. Ready to replace the whole system, they decided to look into commercially available hardware and found it more cost efficient. IOtech's data acquisition product was chosen as the most promising system they had seen. The portable WaveBook provides high-speed sampling, fast data streaming, and multi-channel triggering — imperative features for this application. Additionally, the many signal conditioning options allow easy system expansion, so systems can change as testing grows.

System Design
The "scoring system" is set up in this manner: eight microphones, protected by mounded dirt berms, are placed in front of the targets in two rows of four. As bullets pass the microphones and strike the target, the supersonic shock waves are measured at the eight known locations. Cables, connected to the microphones, run underground to a location away from the target area. There, IOtech's WaveBook portable data acquisition system, digitizes the shock wave signals as they pass through the microphone array. A WBK21, ISA/EPP interface board, allows high-speed data transfer between the WaveBook and a local computer where the data is analyzed and reduced. The data is then passed to a remote computer where the strafing parameters are calculated and displayed for radio relay to the pilot. WBK10A, eight-channel expansion modules, are added to cover additional strafing targets as needed.