A hardware digital correlation scheme for ultrasonic non-destructive testing in explosive environments

There are areas in most offshore oil and gas installations which are extremely difficult to inspect by conventional ultrasonic methods. Owing to the potentially explosive nature of the environment, peak power levels have to b maintained within intrinsically safe limits. Since the surfaces encountered are generally rough and uneven, this can impose a considerable constraint on signal to noise levels in ultrasonic thickness testing and corrosion monitoring. This paper describes the hardware development of a digital correlation system for on-line inspection in such hazardous environments. Based on TTL logic, the system is capable of operation at 20 MHz and may be conveniently extended for use with ultrasonic phased arrays. It also has a considerable potential for biomedical applications. A selection of experimental and simulated results are presented with excellent agreement between theory and practice