Silicon chip thermal sensor coupled into a solid state power source controls temperature or pressure in combustion research. The silicon chip sensing element is embedded in a ceramic support for insulation, and connected to a high resistance bridge which operates the solid state power amplifiers

Gillett, J. D.

English

NASA Technical Reports Server

September 1968	 Brief 68-10337 
NASA TECH BRIEF 
JiT. -	 ---	 aiiiii-	 ii.-iii	
-.	 _-
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.
-	 - 
Temperature or Pressure Controller 
Power	 I	 I	 I Precisio ridge 
n	
f 
Solid- State I	 I	 Solenoid I I -	 I	 1 
 
-Valve 
Temperature-Sensitive 
Material 
The problem: 
A closed-loop temperature controller with higher 
sensitivity, higher reliability and higher power capacity 
than any commercially available unit was required to 
support a combustion research study. 
The solution: 
A thermally sensitive semiconductor material is 
employed as a sensor and coupled into a solid-state 
power control, which operates the propellant valves 
supplying the system being controlled. 
How it's done: 
A silicon chip is used as the thermal sensing ele-
ment. It is embedded in a ceramic support that pro-
vides thermal and electrical insulation from the 
mechanical structure, so that it responds only to the 
temperature variations in the fluid stream that it is 
sensing. The sensing element is connected as the vari-
able leg of a high-resistance bridge which, in turn, 
provides the operating signal to the solid state power 
amplifier that supplies the actuating current for con- 
trol purposes. The unit measures temperatures from 
—423°F to +500°F. For gas stream temperatures 
beiween - 100° and 0°F, control sensitivity better 
than 1°F was obtained. The amplifier output was 10 
amperes into an inductive load on a 28 vdc facility 
valve circuit.	 -	 - 
The very small mass of the sensing element provides 
immediate response, and its large change of resistance
with temperature produces a strong output signal 
from the bridge (15 mv/degree F with 20 vdc input). 
Notes:	 -	 - 
I. This system can also be used as a low-pressure 
controller by using a polymeric sensing element,. 
which changes resistance with pressure. The range 
is adjustable from 3-10 psig. This technique is 
directly applicable to many automation systems 
where low pressure processing requires critical 
control of feed stream pressures. The elimination 
of the conventional electromechanical coupling - 
components increases the reliability of the system. 
2. Inquiries concerning this innovation may be di-
rected to:
	 - 
Technology Utilization Officer - 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10337 
Patent status: 
No patent action is contemplated by NASA. 
-	 Source: J. D. Gillett 
of North American Rockwell Corporation 
-	
under contract to 
Lewis Research Center 
(LEW- 10297) 
Category 01 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Temperature or pressure controller

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