Sec. 1-5] 



MECHANICAL INPUT TRASSDUCERS 



103 



temperature. Briclgman 1 has shown that for many metals at a pres- 

 sure of 12,000 kg/cm 2 and in the temperature range between and 

 100°C the change of b with temperature is of the order of a few per 

 cent; in some metals it is even less. However, the transducer must 

 still be used at a constant temperature, since the resistance of' the 

 probe changes strongly with temperature. 



The transducer is suitable for measuring pressures in the range 

 from zero to above ten thousand kilograms per square centimeter. 



Table 6. Average Pressure Coefficients of Resistance b for 

 Different Metals in the Range 0-12,000 kg/cm 2 at room 



Temperature (25°)* 



* P. W. Bridgman, Proc. Natl. Acad. Sci. U.S., 3, 10 (1917). 



A pressure-sensing element for pressures up to 100,000 atm is de- 

 scribed by Hall. 2 The calibration obtained at room temperature is 

 expected to be reasonably valid under high-temperature operation. 

 The change of resistance for most metals is of the order of 10 per cent 

 for a change of pressure of 10,000 kg/cm 2 ; for manganin it is 2.3 per 

 cent. The linear relationship of Eq. (1) is, of course, only an approxi- 

 mation. The maximum deviation from linearity in the pressure 



*P. W. Bridgman, Proc. Natl. Acad. Sci. U.S., 3, 10 (1917). 

 2 H. T. Hall, Rev. Sci. Instr., 29, 267 (1958). 



