
                                                                     Exhibit 5





                                               November 24, 1997




Emerson Electric Co.
8000 West Florissant Avenue
St. Louis, Missouri 77070


Ladies and Gentlemen:

               I am Assistant General Counsel and Assistant Secretary of
Emerson Electric Co. ("Emerson").

               In connection with Emerson's Registration Statement on Form S-4
(the "Registration Statement") filed with the Securities and Exchange
Commission under the Securities Act of 1933, as amended (the "Securities
Act"), relating to the registration by Emerson of shares (the "Shares") of
common stock, par value $.50 per share, of Emerson to be issued in connection
with the merger of Emersub LVII, Inc. ("Merger Subsidiary"), a wholly-owned
subsidiary of Emerson, with and into Computational Systems, Incorporated
("CSI") pursuant to the terms of the Agreement and Plan of Merger dated as of
October 17, 1997 among Emerson, CSI and Merger Subsidiary (the "Merger
Agreement"), I have examined originals or copies, certified or otherwise
identified to my satisfaction, of such documents, corporate records,
certificates and other instruments, and have conducted such other
investigations of fact and law, as I have deemed necessary or advisable for
the purposes of this opinion.

               In rendering this opinion I have assumed that prior to the
issuance of any of the Shares (i) the Registration Statement, as then amended,
will have become effective under the Securities Act, (ii) the stockholders of
CSI will have approved and adopted the Merger Agreement and (iii) the
transactions contemplated by the Merger Agreement will have been consummated.

               On the basis of the foregoing, I am of the opinion that the
Shares have been duly authorized and the Shares, when issued and delivered in
accordance with the terms and conditions of the Merger Agreement, will be
validly issued, fully paid and non-assessable.

               I am a member of the Bar of the State of Missouri and the
foregoing opinion is limited to the laws of the State of Missouri and the
federal laws of the United States of America.

               I hereby consent to the filing of this opinion as an exhibit to
the Registration Statement and to the use of my name under the caption "Legal
Matters" in the Proxy Statement/Prospectus which is a part of the Registration
Statement.

                                    Very truly yours,

                                    /s/ Harley M. Smith
                                    -------------------
                                    Harley M. Smith



