Overlay is aligned with four calibration dots so it is not affected by CRT drift or changes in vertical or horizontal gain when producing Nyquist /frequency-response phase/amplitude/ plots. Method produces over 50 plots per hour

Freeman, J. M.

Shoup, E. L.

English

NASA Technical Reports Server

June 1970	 Brief 70-10311 
NASA TECH BRIEF 
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. 
Computerized Polar Plots by a Cathode Ray Tube/Grid Overlay Method 
90 
180
270
Completed Plot 
The problem: 
To develop a technique for producing fast, accurate 
Nyquist (frequency-response phase/amplitude) plots. 
The solution: 
Use a CRT plotter with a transparent grid overlay. 
The overlay is aligned with four calibration dots and 
therefore is not affected by CRT drift or changes in 
vertical or horizontal gain. 
How it's done: 
The plot tapes are programmed to plot the data 
trace, the four calibration dots, and the labeling. The 
plots are traced on special paper producing a perma-
nent, hard copy. A grid overlay is chosen that aligns 
with the calibration dots on the hard copy plot (see 
Figure) and the two are taped together. 
Rapid and accurate hard copy printouts and 
duplicates of polar grid plots or tracings can be ob-
tained using this method. Advantages are: (I) plot is 
not affected by cathode ray tube; (2) changes in vertical 
and horizontal gain do not affect the reading; (3) data 
trace is traced four times (producing heavier line 
weight); and (4) previous methods produced about 6 
plots per hour; this method produces over 50. 
The grid overlays are made by drawing the grid 
pattern, 16 inches in diameter, on a polyester resin 
and then reducing to a standard 6 inch size. 
Notes: 
I. This innovation may be of interest to personnel 
engaged in industrial research, educational re-
search, and industrial temperature/pressure moni-
toring. The technique can be used wherever polar 
plots established from a computer are utilized. 
2. No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B70-1031 I 
Patent status: 
No patent action is contemplated by NASA. 
Source: Edward L. Shoup and James M. Freeman of 
The Boeing Company 
under contract to 
Marshall Space Flight Center 
(M FS- 14464) 
Category 03 
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=19700000299 2020-03-17T00:21:38+00:00Z


Computerized polar plots by a cathode ray tube/grid overlay method

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server