<PAGE>
 
                                                                     EXHIBIT 3.1

                             ARTICLES OF AMENDMENT
                            AMENDING AND RESTATING
                           ARTICLES OF INCORPORATION
                                      OF
                           DIAMETRICS MEDICAL, INC.


1.   The name of the corporation is Diametrics MedicaL, Inc., a Minnesota
corporation.

2.   The document entitled "Amended and Restated Articles of Incorporation of
Diametrics Medical, Inc." marked as Exhibit A attached hereto, contains the full
text of the amendments to the articles of incorporation of Diametrics Medical,
Inc.

3.   The date of adoption of the amendment by the board of directors of such
corporation was as of April 21, 1994.

4.   The date of adoption of the amendment by the shareholders of such
corporation was May 3, 1994.

5.   The amendment has been adopted pursuant to Chapter 302A of the Minnesota
Business Corporation Act.

          IN WITNESS WHEREOF, the undersigned, the Secretary of Diametrics
Medical, Inc., being duly authorized on behalf of Diametrics Medical, Inc., has
executed this document on this 21st day of June, 1994.


                                    /s/ Kenneth L. Cutler
                                    ------------------------------
                                    Kenneth L. Cutler
                                    Secretary
<PAGE>
 
                                                                       EXHIBIT A

                AMENDED AND RESTATED ARTICLES OF INCORPORATION
                                      OF
                           DIAMETRICS MEDICAL, INC.


          The following Amended and Restated Articles of Incorporation shall
supersede and take the place of the existing Amended and Restated Articles of
Incorporation and all amendments thereto:

                               ARTICLE 1.  NAME
                               ----------------

          The name of the corporation is Diametrics Medical, Inc.

                         ARTICLE 2.  REGISTERED OFFICE
                         -----------------------------

          The address of the registered office of the corporation is 2658 Patton
Road, Roseville, Minnesota 55113.

                         ARTICLE 3.  AUTHORIZED SHARES
                         -----------------------------

1.  Authorized Shares.
    ----------------- 

          The total number of shares of capital stock which the corporation is
authorized to issue shall be 25,000,000 shares, consisting of 20,000,000 shares
of common stock, par value $.01 per share ("Common Stock"), and 5,000,000 shares
of preferred stock, par value $.01 per share ("Preferred Stock").

2.  Common Stock.
    ------------ 

          All shares of Common Stock shall be voting shares and shall be
entitled to one vote per share.  Holders of Common Stock shall not be entitled
to cumulate their votes in the election of directors and shall not be entitled
to any preemptive rights to acquire shares of any class or series of capital
stock of the corporation.  Subject to any preferential rights of holders of
Preferred Stock, holders of Common Stock shall be entitled to receive their pro
rata share, based upon the number of shares of Common Stock held by them, of
such dividends or other distributions as may be declared by the board of
directors from time to time and of any distribution of the assets of the
corporation upon its liquidation, dissolution or winding up, whether voluntary
or involuntary.

3.  Preferred Stock.
    --------------- 

     The board of directors of the corporation is hereby authorized to provide,
by resolution or resolutions adopted by such board, for the issuance of
Preferred Stock 
<PAGE>
 
from time to time in one or more classes and/or series, to establish the
designation and number of shares of each such class or series, and to fix the
relative rights and preferences of the shares of each such class or series, all
to the full extent permitted by the Minnesota Business Corporation Act, Section
302A.401, or any successor provision. Without limiting the generality of the
foregoing, the board of directors is authorized to provide that shares of a
class of series of Preferred Stock:

          (a)  are entitled to cumulative, partially cumulative or noncumulative
     dividends or other distributions payable in cash, capital stock or
     indebtedness of the corporation or other property, at such times and in
     such amounts as are set forth in the board resolutions establishing such
     class or series or as are determined in a manner specified in such
     resolutions;

          (b)  are entitled to a preference with respect to payment of dividends
     over one or more other classes and/or series of capital stock of the
     corporation;

          (c)  are entitled to a preference with respect to any distribution of
     assets of the corporation upon its liquidation, dissolution or winding up
     over one or more other classes and/or series of capital stock of the
     corporation in such amount as is set forth in the board resolutions
     establishing such class or series or as is determined in a manner specified
     in such resolutions;

          (d)  are redeemable or exchangeable at the option of the corporation
     and/or on a mandatory basis for cash, capital stock or indebtedness of the
     corporation or other property, at such times or upon the occurrence of such
     events, and at such prices, as are set forth in the board resolutions
     establishing such class or series or as are determined in a manner
     specified in such resolutions;

          (e)  are entitled to the benefits of such sinking fund, if any, as is
     required to be established by the corporation for the redemption and/or
     purchase of such shares by the board resolutions establishing such class or
     series;

          (f)  are convertible at the option of the holders thereof into shares
     of any other class or series of capital stock of the corporation, at such
     times or upon the occurrence of such events, and upon such terms, as are
     set forth in the board resolutions establishing such class or series or as
     are determined in a manner specified in such resolutions;

                                       2
<PAGE>
 
          (g)  are exchangeable at the option of the holders thereof for cash,
     capital stock or indebtedness of the corporation or other property, at such
     times or upon the occurrence of such events, and at such prices, as are set
     forth in the board resolutions establishing such class or series or as are
     determined in a manner specified in such resolutions;

          (h)  are entitled to such voting rights, if any, as are specified in
     the board resolutions establishing such class or series (including, without
     limiting the generality of the foregoing, the right to elect one or more
     directors voting alone as a single class or series or together with one or
     more other classes and/or series of Preferred Stock, if so specified by
     such board resolutions) at all times or upon the occurrence of specified
     events; and

          (I)  are subject to restrictions on the issuance of additional shares
     of Preferred Stock of such class or series or of any other class or series,
     or on the reissuance of shares of Preferred Stock of such class or series
     or of any other class or series, or on increases or decreases in the number
     of authorized shares of Preferred Stock of such class or series or of any
     other class or series.

Without limiting the generality of the foregoing authorizations, any of the
rights and preferences of a class or series of Preferred Stock may be made
dependent upon facts ascertainable outside the board resolutions establishing
such class or series, and may incorporate by reference some or all of the terms
of any agreements, contracts or other arrangements entered into by the
corporation in connection with the issuance of such class or series, all to the
full extent permitted by the Minnesota Business Corporation Act.  Unless
otherwise specified in the board resolutions establishing a class or series of
Preferred Stock, holders of a class or series of Preferred Stock shall not be
entitled to cumulate their votes in any election of directors in which they are
entitled to vote and shall not be entitled to any preemptive rights to acquire
shares of any class or series of capital stock of the corporation.

                       ARTICLE 4.  NO CUMULATIVE VOTING
                       --------------------------------

          There shall be no cumulative voting by the shareholders of the
corporation.

                       ARTICLE 5.  NO PREEMPTIVE RIGHTS
                       --------------------------------

          The shareholders of the corporation shall not have any preemptive
rights to subscribe for or acquire securities or rights to purchase securities
of any class, kind or series of the corporation.

                                       3
<PAGE>
 
                    ARTICLE 6.  WRITTEN ACTION BY DIRECTORS
                    ---------------------------------------

          An action required or permitted to be taken at a meeting of the board
of directors of the corporation may be taken by a written action signed, or
counterparts of a written action signed in the aggregate, by all of the
directors unless the action need not be approved by the shareholders of the
corporation, in which case the action may be taken by a written action signed,
or counterparts of a written action signed in the aggregate, by the number of
directors that would be required to take the same action at a meeting of the
board of directors of the corporation at which all of the directors were
present.

                        ARTICLE 7.  DIRECTOR LIABILITY
                        ------------------------------

          To the fullest extent permitted by the Minnesota Business Corporation
Act as the same exists or may hereafter be amended, a director of this
corporation shall not be liable to this corporation or its shareholders for
monetary damages for breach of fiduciary duty as a director.

                                       4
<PAGE>
 
                                 AMENDMENT TO
                             AMENDED AND RESTATED
                           ARTICLES OF INCORPORATION
                                      OF
                           DIAMETRICS MEDICAL, INC.


1.   The name of the corporation is Diametrics Medical, Inc.

2.   Attached hereto as Exhibit A is the full and complete text of the
     amendments to Article VIII of the Amended and Restated Articles of
     Incorporation of Diametrics Medical, Inc.

3.   The date of adoption of the amendment by the board of directors of such
     corporation was April 17, 1996.

4.   The date of adoption of the amendment by the shareholders of such
     corporation was June 27, 1996.

5.   The amendment has been adopted pursuant to Chapter 302A of the Minnesota
     Business Corporation Act.

          IN WITNESS WHEREOF, the undersigned, the Secretary of Diametrics
Medical, Inc., being duly authorized on behalf of Diametrics Medical, Inc., has
executed this document on this 29th day of January, 1997.


                                    /s/ Kenneth L. Cutler
                                    -----------------------------
                                    Kenneth L. Cutler
                                    Secretary
<PAGE>
 
                                                                       EXHIBIT A

                                 ARTICLE VIII

     The Board of Directors shall have the power, to the extent permitted by
law, to adopt, amend or repeal the Bylaws of this corporation, subject to the
power of the shareholders to adopt, amend or repeal such Bylaws.  Bylaws fixing
the number of directors or their classifications, qualifications or terms of
office, or prescribing procedures for removing directors or filling vacancies in
the Board may be adopted, amended or repealed only by the affirmative vote of
the holders of 80% of the outstanding shares of Common Stock entitled to vote.

     The number of directors shall be no less than three nor more than twenty
and shall be established by resolution of the Board of Directors.  The number of
directors may be increased or decreased from time to time by a resolution
adopted by the holders of at least 80% of the outstanding shares of Common Stock
entitled to vote.  In case of any increase or decrease in the number of
directors, the increase or decrease shall be distributed among the several
classes of directors as equally as possible as shall be determined by the Board
of Directors or by the holders of at least 80% of the outstanding shares of
Common Stock entitled to vote.  The affirmative vote of shareholders holding at
least 80% of the outstanding shares of Common Stock entitled to vote at an
election of directors may remove any or all of the directors from office at any
time, with or without cause.

     Notwithstanding any other provisions of these Restated Articles of
Incorporation or the Bylaws of the corporation or the fact that a lesser
percentage may be specified by law, these Restated Articles of Incorporation or
the Bylaws of the corporation, the affirmative vote of the holders of at least
80% of outstanding shares of Common Stock entitled to vote shall be required to
amend or repeal all or any portion of this Article VIII; provided, however, that
if the Continuing Directors shall be majority vote of all Continuing Directors
have adopted a resolution approving the amendment or repeal proposal and have
determined to recommend it for approval by the holders of Common Stock, then the
vote required shall be the affirmative vote of the holders of at least a
majority of the outstanding Common Stock entitled to vote.

     The term "Common Stock" shall mean the Common Stock, par value $.01 per
share, of the corporation.

     The term "Continuing Director" shall mean any member of the Board of
Directors of the corporation who is unaffiliated with a Controlling Person and
was a member of the Board prior to the time that the Controlling Person became a
Controlling Person, and any successor of a Continuing Director who is
unaffiliated with a Controlling Person and is recommended or elected to succeed
a Continuing Director by a majority of all Continuing Directors.

     The term "Controlling Person" shall mean any Person who beneficially owns a
number of shares of Common Stock, whether or not such number includes shares not
then issued, which exceeds a number equal to ten percent of the outstanding
shares of Common Stock.

     The term "Person" shall mean an individual, a corporation, a partnership,
an association, a joint-stock company, a trust, any unincorporated organization
and any other entity or group.
<PAGE>
 
                          CERTIFICATE OF DESIGNATION
                                      OF
                 SERIES I JUNIOR PARTICIPATING PREFERRED STOCK
                                      OF
                           DIAMETRICS MEDICAL, INC.


          The undersigned hereby certifies that the Board of Directors of
Diametrics Medical, Inc. (the "Corporation"), a corporation organized and
existing under the Minnesota Business Corporation Act, duly approved the terms
contained in the following resolution effective on January 29, 1997:

          RESOLVED, that a series of preferred stock of the Corporation is
hereby created, and the designation and amount thereof and the relative rights
and preferences of the shares of such series, are as follows:

          Section 1.  Designation and Amount.  The shares of such series shall
                      ----------------------                                  
be designated as "Series I Junior Participating Preferred Stock" (the "Preferred
Shares") and the number of shares constituting the Preferred Shares shall be
1,000,000.  Such number of shares may be increased or decreased by resolution of
the Board of Directors and any necessary shareholder approval; provided,
                                                               ---------
however, that no decrease shall reduce the number of shares of Preferred Shares
-------
to a number less than the number of shares then outstanding plus the number of
shares reserved for issuance upon the exercise of outstanding options, rights or
warrants or upon the conversion of any outstanding securities issued by the
Corporation convertible into Preferred Shares.

          Section 2.  Dividends and Distributions.
                      --------------------------- 

          (a)  Dividends shall be payable on the Preferred Shares out of funds
legally available for the declaration of dividends only if and when declared by
the Board of Directors.  In no event shall any dividend be paid or declared, nor
shall any distribution be made, on the Common Stock, other than a dividend or
distribution payable solely in shares of Common Stock, unless the holders of the
Preferred Shares shall participate in such dividend on a pro rata basis with the
holders of Common Stock, counting one Preferred Share for each four shares of
Common Stock.  In no event shall any dividend be paid or declared, nor shall any
distribution be made, on any outstanding series of preferred stock, unless the
holders of all of the outstanding Preferred Shares shall participate in such
dividend or distribution on a pro rata basis with the holders of such series of
preferred stock, counting shares of both such series and shares of the Preferred
Shares on an as-if-converted basis.

          (b)  If the Conversion Date (as defined in Section 4 hereof) has not
occurred on or before July 29, 1997, then in such event dividends shall accrue
on the 
<PAGE>
 
Preferred Shares at the rate of 7.0% per annum of the liquidation preference
thereof compounded quarterly from the initial date of issuance of such Preferred
Shares to and including the later of the Conversion Date or the Redemption Date
(as hereinafter defined). Such dividends shall be cumulative from the Accrual
Date and shall be paid on March 31, June 30, September 30 and December 31 of
each year, commencing September 30, 1997. Each such dividend shall be paid to
the holders of record of the Preferred Shares on such record date, not exceeding
15 days preceding the payment date thereof, as shall be fixed by the Board of
Directors. Dividends on account of arrears for any past dividend periods may be
declared and paid at any time, without reference to any regular dividend payment
date, to holders of record on such date, not exceeding 30 days preceding the
payment date thereof, as may be fixed by the Board of Directors.

          Section 3.  Voting Rights.
                      ------------- 

          (a)    Subject to the provision for adjustment hereinafter set forth,
each Preferred Share shall entitle the holder thereof to 2.844 votes on all
matters submitted to a vote of the shareholders of the Corporation.  In the
event the Corporation shall at any time, declare or pay any dividend on the
Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise) into a greater or lesser number of shares of
Common Stock, then in each such case the number of votes per share to which
holders of shares of Preferred Shares were entitled immediately prior to such
event shall be adjusted by multiplying such number by a fraction, the numerator
of which is the number of shares of Common Stock outstanding immediately after
such event and the denominator of which is the number of shares of Common Stock
that were outstanding immediately prior to such event.

          (b)    Unless the vote of the holders of a greater number of shares
shall then be required by law, none of the following actions may be taken by the
Corporation without the approval by vote of the holders of 66.667% of issued and
outstanding Preferred Shares, voting together as a single class:

          (i)    Any amendment, restatement or modification of the Articles of
     Incorporation, By-laws or other governance documents which would reasonably
     be expected to adversely affect the powers, preferences, privileges or
     rights of the Preferred Shares;

          (ii)   Declaration of payment of any dividend or making of any
     distribution on or with respect to the Common Stock;

          (iii)  Purchase, redemption or retirement, directly or indirectly, of
     any shares of capital stock or other equity securities of the Corporation;

                                      -2-
<PAGE>
 
          (iv)   Authorization, creation or issuance of any additional shares of
     capital stock or other securities which would reasonably be expected to
     adversely affect the powers, preferences, privileges or rights of the
     Preferred Shares, or are ranked prior to or pari passu with, the Preferred
                                                 ---- -----                    
     Shares; or

          (v)    A voluntary dissolution, liquidation or winding up.

          (c)  Except as otherwise provided herein or by law, the holders of
Preferred Shares and the holders of Common Stock and any other capital stock of
the Corporation having general voting rights shall vote together as one class on
all matters submitted to a vote of shareholders of the Corporation.

          (d)  Except as set forth herein or required by law, holders of
Preferred Shares shall have no special voting rights and their consent shall not
be required (except to the extent they are entitled to vote with holders of
Common Stock as set forth herein) for taking any corporate action.

          Section 4.  Mandatory Conversion.  When the shareholders of the
                      --------------------                               
Corporation have properly authorized a sufficient number of shares of Common
Stock to allow the conversion of all outstanding Preferred Shares into shares of
Common Stock and appropriate filings have been made with governmental
authorities to effect such authorization (such event being herein referred to as
a "Conversion Event"), which filings will be promptly made by the Corporation,
the Preferred Shares shall automatically be converted into fully paid and
nonassessable shares of Common Stock (and such other securities and property as
the holders of Preferred Shares may be entitled to upon the conversion thereof,
as hereinafter provided) at the Conversion Rate (as hereinafter defined) plus an
amount equal to any accrued and unpaid dividends thereon.  The Corporation shall
give prompt notice of such mandatory conversion by first class mail, postage
prepaid, to the holders of record of the Preferred Shares, addressed to such
holders at their last addresses as shown on the stock books of the Corporation.
The date (the "Conversion Date") of such mandatory conversion shall be the date
of consummation of the Conversion Event.  Each notice of mandatory conversion
shall specify:  the Conversion Date and then-effective Conversion Rate (which
shall be four shares of Common Stock for each Preferred Share, unless otherwise
adjusted hereunder); that the holders of Preferred Shares were deemed to have
become holders of record of Common Stock on the Conversion Date; that, from and
after the Conversion Date, the Preferred Shares were no longer considered
outstanding; and that all rights with respect to the shares of Preferred Shares
(and such other securities and property as the holders of the Preferred Shares
may be entitled to upon the conversion thereof, as hereinafter provided) so
converted terminated on the Conversion Date, except the right to receive Common
Stock (and such other securities and property as the holders of Preferred Shares
may be entitled to upon the conversion thereof, as hereinafter provided) as
herein provided.  On and after the Conversion Date, each holder of Preferred
Shares shall surrender the certificate or certificates evidencing such shares to
the Corporation at a place to be designated 

                                      -3-
<PAGE>
 
in such notice and shall thereupon be entitled to receive the Common Stock (and
such other securities and property as the holders of Preferred Shares may be
entitled to upon the conversion thereof, as hereinafter provided) receivable in
exchange therefor. Notwithstanding that the certificates evidencing any shares
of Preferred Shares mandatorily converted into Common Stock shall not have been
surrendered on the Conversion Date, such shares shall no longer be deemed
outstanding, and the holders thereof shall nevertheless be deemed to have become
holders of record of Common Stock (and such other securities and property as the
holders of Preferred Shares may be entitled to upon the conversion thereof, as
hereinafter provided) on the Conversion Date.

          Except where registration is requested in a name other than the name
of the registered holder, the Corporation will pay any and all documentary stamp
or similar issue or transfer taxes payable in respect of the issue or delivery
of shares of Common Stock on conversion of the Preferred Shares pursuant hereto.

          Section 5.  Reacquired Shares.  Any Preferred Shares purchased,
                      -----------------                                  
converted or otherwise acquired by the Corporation in any manner whatsoever
shall be retired and canceled promptly after the acquisition thereof.  All such
shares shall upon their cancellation become authorized but unissued shares of
preferred stock and may be reissued as part of a new series of preferred stock
subject to the conditions and restrictions on issuance set forth herein, in the
Articles of Incorporation, or in any other certificate of designation creating a
series of preferred stock or any similar stock or as otherwise required by law.

          Section 6.  Liquidation, Dissolution or Winding Up; Rank.  Upon any
                      --------------------------------------------           
liquidation, dissolution or winding up of the Corporation, no distribution shall
be made (1) to the holders of shares of stock ranking junior (either as to
dividends or upon liquidation, dissolution or winding up) to the Preferred
Shares unless, prior thereto, the holders of Preferred Shares shall have
received the greater of (i) $16.00 per share, plus an amount equal to any
accrued and unpaid dividends and distributions thereon, to the date of such
payment, or (ii) an aggregate amount per share, subject to the provision for
adjustment hereinafter set forth, equal to four times the aggregate amount to be
distributed per share to holders of Common Stock, or (2) to the holders of stock
ranking on a parity (either as to dividends or upon liquidation, dissolution or
winding up) with the Preferred Shares, except distributions made ratably on the
Preferred Shares and all such parity stock in proportion to the total amounts to
which the holders of all such shares are entitled upon such liquidation,
dissolution or winding up. In the event the Corporation shall at any time,
declare or pay any dividend on the Common Stock payable in shares of Common
Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise) into a
greater or lesser number of shares of Common Stock, then in each such case the
aggregate amount to which holders of shares of Preferred Shares were entitled
immediately prior to such event under clause (1)(ii) of the preceding sentence
shall be adjusted by multiplying such amount by a fraction the numerator of
which is the 

                                      -4-
<PAGE>
 
number of shares of Common Stock outstanding immediately after such event and
the denominator of which is the number of shares of Common Stock that were
outstanding immediately prior to such event. For the purposes hereof, a
consolidation or merger of the Corporation with or into any other person or
entity, or a sale or transfer of all or substantially all the Corporation's
assets for cash or securities, shall be considered a liquidation, dissolution or
winding up of the Company, unless, with respect to a merger, consolidation or
sale, the holders of shares of Common Stock immediately preceding such merger or
consolidation hold at least a majority of the equity securities of the surviving
entity entitled to vote in the election of directors (or similar governing body)
of the surviving entity.

          So long as any Preferred Shares remain outstanding, no stock of any
class or series of the Corporation shall rank prior to or pari passu with the
                                                          ----------         
Preferred Shares, as to liquidation preference, dividends or distributions.

          Section 7.  Consolidation, Merger, etc.   In case of any
                      ---------------------------                 
reclassification or change of outstanding shares of Common Stock (other than a
change in par value, or as a result of a subdivision or combination), or in case
of any consolidation of the Corporation with, or merger of the Corporation with
or into, any other entity that results in a reclassification, change,
conversion, exchange or cancellation of outstanding shares of Common Stock or
any sale or transfer of all or substantially all of the assets of the
Corporation, each holder of shares of the Preferred Shares then outstanding, if
it has elected not to require a distribution pursuant to Section 6, shall have
the right thereafter to convert the shares of the Preferred Shares held by the
holder into the kind and amount of securities, cash and other property which the
holder would have been entitled to receive upon such reclassification, change,
consolidation, merger, sale or transfer if the holder had held the Common Stock
issuable upon the conversion of the Preferred Stock immediately prior to the
reclassification, change, consolidation, merger, sale or transfer.

          Section 8. Redemption.  (a) The Preferred Shares shall not be
                     ----------                                        
redeemable at the option of the Corporation and shall be redeemable at the
option of the holder thereof only as provided in this Section 8(b).

          (b)  In the event that as of January 29, 1999 (the "Put Date") the
Conversion Date has not occurred and the Corporation has not caused the
Preferred Shares to be registered for inclusion on the automated quotation
system of the National Association of Securities Dealers, Inc. or any national
securities exchange on which a class of the Corporation's equity securities is
listed, the Preferred Shares shall be redeemable at the option of the holder
thereof at a price equal to the greater of (i) Current Market Price on the Put
Date (as hereinafter defined) and (ii) the liquidation preference thereof, plus
accrued and unpaid dividends thereon to the date fixed for redemption (the
"Redemption Price") as of the close of business on the 30th business day
following the Put Date (the "Redemption Date"). Notwithstanding the foregoing,
in the event that the Corporation fails to declare and pay a dividend pursuant
to Section 2(b) above, the Put Date shall be accelerated

                                      -5-
<PAGE>
 
to the payment date that would otherwise apply to such defaulted dividend
payment. The Corporation shall give prompt notice of the Put Date (the "Put Date
Notice") by certified mail, return-receipt requested, to the holders of record
of the Preferred Shares, addressed to such holders at their last addresses as
shown on the stock books of the Corporation. A holder of record of the Preferred
Shares as of the Put Date shall be required to give written notice to the
Corporation of such holder's election to require such redemption (a "Notice of
Redemption") on or before the 20th business day following the date receipt of
such notice is acknowledged. In the event that the Corporation receives Notices
of Redemption from holders representing in excess of 75% of the Preferred Shares
outstanding, the Corporation shall redeem all outstanding Preferred Shares on
the Redemption Date. Notice of Redemption having been given as aforesaid, the
Preferred Shares so to be redeemed shall, on the Redemption Date, become due and
payable at the Redemption Price, and from and after such date such Preferred
Shares shall cease to accrue dividends. Upon surrender of any certificate
representing Preferred Shares for redemption, the record holder of such
Preferred Shares shall be paid by the Corporation the Redemption Price. "Current
Market Price" means four (the "Multiple") times (a) the closing price on the
previous trading day for the Common Stock on the principal stock exchange on
which the Common Stock is traded or (b) if not so traded, the closing price (or,
if no closing price is available, the average of the bid and asked prices) for
such date on the NASDAQ if the Common Stock is listed on the NASDAQ or (c) if
not listed on any exchange or quoted on the NASDAQ, such value as may be
determined in good faith by the Corporation's Board of Directors, which
determination shall be conclusively binding. In the event the Corporation shall
at any time, declare or pay any dividend on the Common Stock payable in shares
of Common Stock, or effect a subdivision or combination or consolidation of the
outstanding shares of Common Stock (by reclassification or otherwise) into a
greater or lesser number of shares of Common Stock, then in each such case the
Multiple shall be adjusted by multiplying such amount by a fraction, the
numerator of which is the number of shares of Common Stock outstanding
immediately after such event and the denominator of which is the number of
shares of Common Stock that were outstanding immediately prior to such event.

          Section 9.  Fractional Shares.  Preferred Shares may be issued in
                      -----------------                                    
fractions of a share which are integral multiples of one one-hundredth of a
share which shall entitle the holder, in proportion to such holder's fractional
shares, to receive dividends, participate in distributions and to have the
benefit of all other rights of holders of Preferred Shares.

                                      -6-
<PAGE>
 
          IN WITNESS WHEREOF, I have subscribed my name this 29th day of
January, 1997.

                                   DIAMETRICS MEDICAL, INC.


                                    /s/ Laurence L. Betterley
                                   -----------------------------------------
                                   Laurence L. Betterley
                                   Chief Financial Officer
<PAGE>
 
                            ARTICLES OF CORRECTION
                                      OF
                           DIAMETRICS MEDICAL, INC.


     In order to correct the Certificate of Designation of Series I Junior
Participating Preferred Stock as filed with the Minnesota Secretary of State on
January 29, 1997, in accordance with the provisions set forth in Minnesota
Statutes Section 5.16, the undersigned hereby makes the following statements:

     1.   The name of the person who filed the instrument is Laurence L.
Betterley.

     2.   The instrument to be corrected is the Certificate of Designation of
Series I Junior Participating Preferred Stock of Diametrics Medical, Inc. filed
with the Minnesota Secretary of State on January 29, 1997.

     3.   The error to be corrected is the number of votes each Preferred Share
entitles its holder to cast, as set forth in Section 3(a) of the Certificate of
Designation.

     4.   The following portion of the Certificate of Designation is hereby set
forth in its corrected form as follows:

     "Section 3.  Voting Rights.
                  ------------- 

          (a)  Subject to the provision for adjustment hereinafter set forth,
each Preferred Share shall entitle the holder thereof to 3.16 votes on all
matters submitted to a vote of the shareholders of the Corporation.  In the
event the Corporation shall at any time, declare or pay any dividend on the
Common Stock payable in shares of Common Stock, or effect a subdivision or
combination or consolidation of the outstanding shares of Common Stock (by
reclassification or otherwise) into a greater or lesser number of shares of
Common Stock, then in each such case the number of votes per share to which
holders of shares of Preferred Shares were entitled immediately prior to such
event shall be adjusted by multiplying such number by a fraction, the numerator
of which is the number of shares of Common Stock outstanding immediately after
such event and the denominator of which is the number of shares of Common Stock
that were outstanding immediately prior to such event.

          (b)  Unless the vote of the holders of a greater number of shares
shall then be required by law, none of the following actions may be taken by the
Corporation without the approval by vote of the holders of 66.667% of issued and
outstanding Preferred Shares, voting together as a single class:

          (i)  Any amendment, restatement or modification of the Articles of
     Incorporation, By-laws or other governance documents which would reasonably
     be expected to adversely affect the powers, preferences, privileges or
     rights of the Preferred Shares;
<PAGE>
 
          (ii)   Declaration of payment of any dividend or making of any
     distribution on or with respect to the Common Stock;

          (iii)  Purchase, redemption or retirement, directly or indirectly, of
     any shares of capital stock or other equity securities of the Corporation;

          (iv)   Authorization, creation or issuance of any additional shares of
     capital stock or other securities which would reasonably be expected to
     adversely affect the powers, preferences, privileges or rights of the
     Preferred Shares, or are ranked prior to or pari passu with, the Preferred
                                                 ---- -----   
     Shares; or

          (v)  A voluntary dissolution, liquidation or winding up.

          (c)  Except as otherwise provided herein or by law, the holders of
Preferred Shares and the holders of Common Stock and any other capital stock of
the Corporation having general voting rights shall vote together as one class on
all matters submitted to a vote of shareholders of the Corporation.

          (d)  Except as set forth herein or required by law, holders of
Preferred Shares shall have no special voting rights and their consent shall not
be required (except to the extent they are entitled to vote with holders of
Common Stock as set forth herein) for taking any corporate action."
<PAGE>
 
          IN WITNESS WHEREOF, I have subscribed my name this 30th day of
January, 1997.

                                   DIAMETRICS MEDICAL, INC.


                                    /s/Laurence L. Betterley
                                   ---------------------------------------------
                                   Laurence L. Betterley
                                   Chief Financial Officer
<PAGE>
 
                             ARTICLES OF AMENDMENT
                                      OF
                           ARTICLES OF INCORPORATION
                                      OF
                           DIAMETRICS MEDICAL, INC.


1.   The name of the corporation is Diametrics Medical, Inc., a Minnesota
     corporation.

2.   The amendment adopted is:

          "PARAGRAPH 1 OF ARTICLE 3 OF THE COMPANY'S AMENDED AND RESTATED
          ARTICLES OF INCORPORATION IS HEREBY AMENDED AS FOLLOWS:

          1.   AUTHORIZED SHARES.
               ----------------- 

                    THE TOTAL NUMBER OF SHARES OF CAPITAL STOCK WHICH THE
                    CORPORATION IS AUTHORIZED TO ISSUE SHALL BE 40,000,000
                    SHARES, CONSISTING OF 35,000,000 SHARES OF COMMON STOCK, PAR
                    VALUE $.01 PER SHARE (`COMMON STOCK'), AND 5,000,000 SHARES
                    OF PREFERRED STOCK, $.01 PAR VALUE PER SHARE (`PREFERRED
                    STOCK')."

3.   The amendment has been adopted pursuant to Chapter 302A of the Minnesota
     Business Corporation Act.

          IN WITNESS WHEREOF, the undersigned, David Giddings, the President,
Chief Executive Officer and  Chairman of Diametrics Medical, Inc., being duly
authorized on behalf of Diametrics Medical, Inc., has executed this document
this 10th day of April, 1997.


                                         /s/ David Giddings
                                        ----------------------------------------
                                        David Giddings
                                        President, Chief Executive Officer and
                                        Chairman