152 MEASUREMENT OF PRESSURES 



5.2. The Hilliar Piston Gauge 



As the discussion of section 5.1 shows, the ball crusher and other 

 types of crusher gauge are most useful as indicators of peak pressure at 

 a shock front. An extension of the basic idea of using plastic deforma- 



COPPER 

 CRUSHER 



STEEL 

 PISTON 



^:7 



B 



(a) 



(b) 



Fig. 5.3 Principle and construction of Hilliar piston gauge. 



tions to make possible indications of pressures at later times was de- 

 veloped by Hilliar and applied by him to a classic investigation (47) of 

 the properties of pressure waves from underwater explosions. The 

 gauge consists of a piston and copper crusher as before, but with the 



