Interference method produces a moire pattern having a shape correlated with the lead spacing. A continuous check of the spacing is possible if the material between the leads is translucent. Technique is quick, accurate, convenient, and simple to operate

Angele, W.

English

NASA Technical Reports Server

August 1970
	 Brief 70-10015 
RH. 1313 
XO12 
KSCHQSO 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
Information, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Measuring the Conductor Spacing in Flat Conductor Cables 
One of the principal difficulties in manufacturing 
flat conductor cable has been the lack of a method 
to ensure quickly and accurately that the spacing of 
the leads is uniform. The standard inspection method 
involves moving the cable across the objective of a 
toolmaker's microscope with. a calibrated spindle. 
Data on the position of each individual lead must be 
collected, tabulated, and plotted -before it can be as-
certained whether or not th'e lead , spacings are within 
tolerance. 
This time-consuming, tedious process can now be 
eliminated. A newly , developed interference method 
produces a moire pattern, the shape of which is cor-
related with the lead spacing. In addition to the ad-
vantages of speed, accuracy, convenience, and sim-
plicity of operation, this technique permits continuous 
rather than spot checking of the spacing. The only 
requirement is that the material between the leads on 
the test cable be translucent. Shielded cables must 
therefore be tested before the shields are added. 
Moire patterns are produced by interference be-
tween two periodic geometric designs. In this applica-
tion, one design is formed by the flat conductors in 
the cable to be measured; the other is a precision-
fabricated master design of uniformly spaced rectan-
gular bars. When the two designs are superimposed, a 
moire pattern appears, with a dark band in each 
region where the bars of one design lie over the spaces 
of the other, and light zones where the bars of the two 
designs coincide. Given the situation that the two 
designs are superimposed at a precisely known, small 
angle, the following typical patterns may be observed: 
(1) if the master and the test designs are uniform and
identically spaced, the moire pattern will consist of 
equally spaced, linear bands approximately perpen-
dicular to the bars; (2) if the master and the test de-
signs are uniform, but different in spacing, the pattern 
will consist of equally spaced, linear bands inclined 
with respect to the bars at an angle which is a known 
function of the difference in spacing; and (3) if there 
is any nonuniformity of spacing in the test design, the 
moire pattern will consist of wavy, angular, or ragged- 
edged dark bands, the slope of which at any point 
determines the spacing of the nearby conductors. 
In the referenced report, the various moire patterns 
are explained and the method of calculating the inter-
conductor spacing from the moire slant angle is given. 
Note: 
The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65) 
Reference: 
NASA-TM-X-53843 (N69-35124), Meas-
uring the Conductor Spacing in Flat 
Conductor Cables 
Patent status: 
No patent action is contemplated by NASA. 
Source: W. Angele 
Marshall Space Flight Center 
(M FS-20560) 
Category 08 
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=19700000015 2020-03-17T00:00:46+00:00Z


Measuring the conductor spacing in flat conductor cables

Interferometric measurement of conductor spacing in flat conductor cable

Measuring the conductor spacing in flat conductor cables

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