Miniature pressure transducers with diffused, heavily doped silicon strain-gage sensor elements, operates over a wide temperature range. Small thermal mass combined with close coupling between a metallic diaphragm and sensor elements minimizes sensitivity to temperature transients

Bowman, R.

Burns, J.

Mc Lellan, W.

English

NASA Technical Reports Server

July 1968
	 Brief 68-10262 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Silicon Strain Sensors Enable

Pressure Measurement at Cryogenic Temperatures 
Diffused, heavily doped silicon strain-gage sensor 
elements have been developed for operation in pres-
sure transducers over a wide temperature range. Op-
timization of gage characteristics, excitation-source 
impedance, bridge-circuit parameters, and transducer 
structure has led to the design of miniature pressure 
transducers which exhibit zero and sensitivity shifts 
of less than ± 3 percent of full scale throughout the tem-
perature range from +250° to —450°F (700°F tem-
perature span). Small thermal mass combined with 
close coupling between a metallic diaphragm (force 
summing member) and sensor elements minimizes 
sensitivity to temperature transients. Silicon was se-
lected as the most satisfactory semiconductor material 
from which to fabricate wide temperature range strain 
sensors for the following reasons: (1) Silicon offers 
the best combination of piezoresistiveand mechanical 
properties of any known semiconductor material. (2) 
Silicon device processing techniques are well developed 
and readily adaptable to fabrication of miniature gage 
elements. (3) The piezoresistive behavior of silicon is 
sufficiently well known to permit prediction of gage 
characteristics on the basis of impurity type and con-
centration. 
Although the sensors were specially developed for 
low-temperature operation, they perform equally well 
at much higher temperatures, thus providing continu-
ous measurement capability over a 700°F temperature 
range. 
Prototype pressure transducers (0.8-inch diameter 
X 1.1-inch length) incorporating the silicon sensor 
elements have met the following specifications: 
Pressure Range: 0 to 2000 psig 
Combined Nonlinearity and Hysteresis: 
less than 1.1% F.S. above —320°F and less than 
35% F.S. from —320°F to —450°F
Repeatability: 
less than 1% F.S., except for one unit (of three) 
which indicated 9.5% at —446°F only 
Compensated Temperature Range: —320° to +250°F 
Temperature Effects within Specified Temperature 
Range: 
0.321%/°F maximum from —108° to +250°F zero 
2.2%/°F maximum from —320° +250°F 
0.064%/°F maximum from —320°F to + 250* 1 Full 0.074%/°F maximum from —446° to +250°F Range 
Excitation: 1 Ov 
Output Voltage: 30 my
 F.S. 10% at 75°F 
Frequency Response: 1000 Hz 
Acceleration: 50 g, 200 to 3000 Hz 
Accleration Effect: 
less than 0.1% F.S./50 g or 0.002% F.S./1 g 
Shock: 1000 g (1 ms duration with no damage) 
Note: 
Complete details may be obtained from: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B68-10262 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D. C. 20546. 
Source: R. Bowman, J. Burns, 
and W. McLellan 
of Electro-Optical Systems, Inc. 
under contract to 
Marshall Space Flight Center 
(MFS-14703) 
Cateprcsrv 01 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000262 2020-03-12T06:11:30+00:00Z


Silicon strain sensors enable pressure measurement at cryogenic temperatures

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