607 
37 
TABLE 4 
Piezoelectric Calibration Constants of Typical Tourmaline Gages 
coulombs per pounds 
per square inch 
for Gage 275 is based on the measurement of 36 oscillograms like the one in 
Figure 21. The deviation given in Column 3 is in every instance the standard 
deviation. It will be seen that the KA determinations for a given gage are 
internally consistent to within one or two per cent. 
It is interesting to compare these KA values with those obtained 
for these same crystals by the Exploration Laboratory of the Stanolind Com- 
pany,* from whom the plated crystals are procured. Their figures are listed 
in Column 4, and the percentage differences between these values and those 
obtained at the Taylor Model Basin are given in Column 5. The TMB calibra- 
tions differ from those of Stanolind by 2 per cent or less. It should be 
emphasized that the two sets of calibrations were performed by independent 
observers using different techniques. One of these gages, XT-503, was pre- 
viously calibrated by the Underwater Explosives Research Laboratory at Woods 
Hole; the value obtained there is in agreement with Stanolind's within 1 
per cent. 
From the value of KA and the measured area of A of the crystals 
listed in Column 6, the piezoelectric constant K of the tourmaline used in 
these gages is computed. The values of K deduced from the Taylor Model Basin 
determinations and from those of the Stanolind Laboratory are listed in Col- 
umns 7 and 8 respectively. These figures may be compared with those computed 
from piezoelectric moduli given in the International Critical Tables (10). 
Using the moduli of Riecke and Voigt found in these tables, the piezoelectric 
constant of tourmaline along its electrical axis when the crystal is subjected 
Dr. Daniel Silverman of the Stanolind Company carried out these calibrations with a microcoulometer. 
