FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

performed by a video detector stage.
Peak detector and x-y display modules art also included to allow
the ultrasonics subsystem to be used, along with the scan
controller, in a stand-alone mode. During scanning, the x-y
display interface combines the output from the peak detector with
position information from the scanner controller to produce realtime
modified c-scan images on the built-in crt display or on an
external x-y chart recorder.
Outputs are provided from each stage to allow viewing on an
oscilloscope or digitization by the host computer.
2.h Host Computer
The host computer is a Multibus-based system utilizing an Intel
8086 microprocessor and 8087 math co-processor, 768 kilobytes of
program memory, and both fixed and floppy-based mass storage. A
digital transient recorder (DTR) installed on the Multibus acts
as a high-speed analog-to-digital (a/d) converter, permitting the
host to digitize and store ultrasonic signal data. The DTR can
digitize arbitrary signals at rates up to 20HHz, while repetitive
waveforms may be effectively sampled at up to 160 MHz.
A colour graphics module, consisting of 3 additional Multibus
boards, provides a resolution of 1024 by 769 points. Up to 16
colours can be displayed simultaneously, chosen from a pallette
of 4096. Support for 3~dimensional graphics is provided by an
ACM-SIGGRAPH Core library of subroutines (8).
3. SYSTEM OPERATION
Initially, the host prompts the user for all the necessary
scanning parameters: the axes to be used, the scan dimensions and
velocity, the sample interval, and the number of transducers.
These are then sent to the slave, followed by a signal for
scanning to begin.
During an inspection, the slave signals the host computer
whenever the scanning bridge reaches a position at which data is
to be acquired. Then, for each of the transducers in use, the
slave enables the appropriate ultrasonic channel while the host
triggers the puiser and the DTR. Once triggered, the DTR
collects 4096 amplitude data points, each with a resolution of 1
part in 256. While these may be stored directly for later
analysis, additional peak detection processing is usually
performed to reduce the stored data to a manageable amount.
If time-of-f1ight data is being collected, the host extracts from