The low frequency ultrasonic equipment used by NCEL is commercially 

 available from James Electronics, Inc., Chicago, 111. This ultrasonic 

 equipment is used routinely during field inspections of lumber, utility 

 poles, and concrete terrestrial structures. The entire system (Figure 6) 

 consists of two lead-zirconate-titanate ceramic piezoelectric transducers 

 mounted in stainless steel cases; a portable ultrasonic digital readout 

 meter (called the V-meter) equipped with a factory-installed adapter to 

 permit direct readout on an oscilloscope; and an analog display unit 

 that converts digital transit time measurements into analog form. 

 Initial ultrasonic tests determined that transit time measurements were 

 not a reliable or accurate measure of cross-sectional wood loss; conse- 

 quently, the analog display unit that converts digital transit time 

 measurements to analog form was not employed. A schematic of the ultra- 

 sonic test system configuration is shown in Figure 7. 



Figure 6. Transducers, ultrasonic v-meter and analog display unit. 



The ultrasonic parameter that indicated the highest potential for 

 correlation to the amount of cross-sectional wood loss was the RMS ampli- 

 tude of the ultrasonic signal received. A computer program to calculate 

 this value was written for the Tektronix 4052 computer. 



17 



