Magnetoresistor monitors the action of relays without disturbing circuit parameters or degrading relay performance. The magnetoresistor measures the relay magnetic flux produced under transient conditions to establish the characteristic signature of the relay

Krebs, D. Q.

English

NASA Technical Reports Server

December 1966	 Brief 66-10650 
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. 
Magnetoresistor Monitors Relay Performance 
The problem: 
To monitor the action of relays without disturbing 
circuit parameters or degrading relay performance. 
Normally, relay performance monitoring has been 
limited to fully open or fully closed position indica-
tions plus coil circuit condition. Steady-state or 
transient position data cannot be obtained through 
current monitoring because the steady-state current is 
dependent only on the dc resistance of the coil. 
The solution: 
A technique that establishes the characteristic 
signature of a relay by measuring the magnetic flux 
produced under transient conditions.
How it's done: 
A magnetoresistor is placed in a recess in the con-
tact end of the relay core. This probe is operated by 
its own power supply and, through a bridge circuit, 
its reaction to change in relay magnetic flux is indi-
cated on a voltmeter and displayed on an oscilloscope. 
By photographing the oscilloscope display, voltage 
and current conditions related to time are made avail-
able to determine the characteristic signature of a 
given relay. Such parameters as contact travel time, 
time for coil current to reach a steady-state condition, 
coil voltage condition, etc. afford a clear picture of 
relay operating characteristics.
(continued overleaf) 
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=19660000648 2020-03-11T17:41:46+00:00Z
Notes: 
1. Many malfunctions, such as lack of armature 
movements, friction, welded contacts, and low 
coil voltage may be determined from the transient 
waveforms.' 
2. This device permits relay monitoring with ' a single 
passive sensor that does not affect relay operation 
or reliability. 
3. Inquiries concerning this innovation may be di-
rected to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10650
Patent status: 
No patent action is contemplated by NASA. 
Source: Darrel Q. Krebs

of The Boeing Company

under contract to

Marshall Space Flight Center

(M-FS-1754) 
Brief 66-10650	 Category 01


Magnetoresistor monitors relay performance

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