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APPENDIX 
CONSTRUCTION OF THE QUARTZ PIEZOELECTRIC GAGE 
Figure 3 is a view of the quartz gage with a section cut away to 
show the various components. The principal parts of the gage will first be 
described, then the details of its construction. 
Quortz Crystal Brass Cover 
Brass Pan 
Solder Joint 
Electrode 
Ss 
as 
VA 
Shellac Bross Tube 
Bokelite Bushing 
Solder 
Insulated Wire 
from Electrode 
Copper Cable _ 
Filled with Wox 
Figure 3 - Components of the TMB Quartz Piezoelectric Gage 
The brass housing consists of three parts: a "pan" which contains the crystal; a cover; and a brass 
tube which is silver-soldered to the pan. A cylindrical, X-cut quartz crystal is cemented on one side 
to an electrode consisting of a thin copper disk, and on the other to the cover of the brass housing, 
through which it is grounded. The use of a copper disk for the electrode obviates the trouble of 
electroplating. Laterally the crystal is surrounded by an air gap which is required because quartz 
is insensitive to isotropic pressure. It is the need for this air gap which makes a housing necessary. 
DESCRIPTION OF THE PRINCIPAL PARTS 
The copper electrode is insulated from the brass pan by a thin 
sheet of mica. It is connected to the central lead wire, which is covered 
with enamel and a double layer cf glass fiber. The space between this insu- 
lated wire and the concentric copper tube is filled with ceresin wax. Near 
its entrance into the pan the wire is insulated from the brass tube by a 
bakelite bushing. The crystal is so oriented that a compressional force pro- 
duces a negative charge on the surface next to the copper electrode. When 
the gage is in use, the electrode is connected to the grid of an amplifier 
tube; thus the grid is charged negatively during compression. The brass 
housing is sealed watertight by soft-soldering the cover to the pan. 
