Reversing, thermal, motor-driven device positions magnetometer sensors for checking zero offset. The device alternately positions two sensors at fixed positions 90 degrees apart. The thermal motor is fabricated completely of nonmagnetic materials

Kerwin, W. J.

Scott, S. G.

English

NASA Technical Reports Server

• Over-
Center 
Linkage
Output 
Shaft
Bimetallic Coils 
Resistance Coils 
ut 
he 
March 1966	 Brief 66-10078 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Thermal Motor Positions Magnetometer Sensors 
The problem: 
In checking magnetometer sensors for zero offset, 
it is necessary to change their orientation frequently 
and on command. It is necessary that the mechanism 
used develop minimum magnetic field. 
The solution: 
A reversing, thermal, motor-driven device that 
alternately positions two magnetometer sensors at 
fixed positions 90° apart. The thermal moto r is fabri-
cated completely of nonmagnetic materials. 
How it's done: 
Two bimetallic coils are mounted oppositely on a 
common shaft made of solid and hollow sections. The 
hollow sections contain counterwound, double 
threaded resistance coils that generate no magnetic 
field. The bimetallic coils are mounted on these hol-
low sections with their external ends anchored to a 
torque arm. The motor output shaft is attached to a 
spring-loaded, over-center linkage that engages the 
sensor shaft above the motor. 
Heating of one resistance element causes its bi-
metallic coil to drive the output shaft in a clockwise 
direction to a point where the over-center linkage 
flips the sensor shaft through a 90° turn. When that 
resistance element has cooled, current applied to the 
other heater results in a reversal and the sensors are 
rotated 90° in a counterclockwise direction to their 
original position. Torque from one bimetallic coil is 
transmitted to the other through the torque arm, so 
that no energy is expended in overcoming spring 
resistance in the dormant coil, as the case would be if 
each coil were independently enclosed. A stop provides 
crntinued overleal) 
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.
https://ntrs.nasa.gov/search.jsp?R=19660000078 2020-03-11T17:34:16+00:00Z
positive positioning of the sensors in each cycle at 
900
 from their previous position. 
Notes 
1. Ambient temperature gradients have no effect 
because the two bimetallic coils act in opposition, 
thus cancelling mutual contraction or expansion. 
2. Energy of approximately 300 watt seconds is re-
quired to rotate the sensors. Transit time is ap-
proximately 0.2 second. 
3. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California, 94035 
Reference: B66-10078
Patent status: 
This invention is owned by NASA, and a patent

application has been filed. Royalty-free, non-exclu-

sive licenses for its commercial use will be granted by

NASA. Inquiries concerning license rights should be

madeto NASA, Code GP, Washington, D.C., 20546.

Source: William J. Kerwin and

Stanley G. Scott

(ARC-Si)
n' 
Brief 66-10078
	 Category 05


Thermal motor positions magnetometer sensors

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