<PAGE>
 
                                                                    Exhibit 10.2


                                 PUT OPTION AND
                            STOCK PURCHASE AGREEMENT

         This Agreement (this "Agreement") is made this 1st day of October 1998
(the "Effective Date"), by and among Diametrics Medical, Inc., a Minnesota
corporation, with its principal place of business at 2658 Patton Road,
Roseville, Minnesota 55113 (the "Company"), and Johnson & Johnson Development
Corporation, a New Jersey corporation, with its principal place of business at
One Johnson & Johnson Plaza, New Brunswick, New Jersey 08933 (the "Purchaser").

                                   BACKGROUND

         A. The Company and Johnson & Johnson Professional Inc., a New Jersey
corporation ("JJPI"), have entered into a Distribution Agreement of even date
herewith (the "Distribution Agreement").

         B. In connection with the Distribution Agreement, the Company desires
to sell shares of its common stock, par value $.01 (the "Common Stock"), and the
Purchaser desires to purchase the same, each on the terms and subject to the
conditions set forth herein.

         C. The Company and the Purchaser desire to make certain
representations, warranties, covenants and agreements in connection with, and
establish various conditions precedent to, the sale and purchase of shares of
the Company's Common Stock.

         NOW, THEREFORE, in consideration of the mutual covenants contained in
this Agreement, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Company and the Purchaser
hereby agree as follows:

         Section 1. Authorization and Issuance of the Securities. Subject to the
terms and conditions of this Agreement, the Company has, or before the Initial
Closing (as defined in Section 3.1 below) will have, authorized the issuance and
delivery to the Purchaser of the Put Shares (as defined in Section 2.3 below).

         Section 2. Put Right of the Company.

         2.1 Put Right. The Company shall have, and is hereby granted, the right
and option to sell to the Purchaser, and to require the Purchaser to purchase,
the Put Shares upon and subject to the terms and conditions hereinafter set
forth (the said right and option to sell the Put Shares being hereinafter called
the "Put"). The Company may exercise the Put at any time during the period of
one year from the opening of business on October 1, 1998, to the close of
business on September 30, 1999 (the "Put Period"), by giving the Purchaser
notice of its election to sell the Put Shares, or a part thereof, as hereinafter
provided. During the Put Period, the Put may be exercised in whole at any time
or in part from time to time; provided, however, no partial exercise shall be
for Put Shares valued in the aggregate less than $1,000,000, and the Company
shall be entitled to exercise the Put no more than twice during the Put Period.
<PAGE>
 
         2.2 Put Notification Date; Put Date. The Company shall provide written
notice to the Purchaser of its election or partial election to exercise the Put,
which notice shall specify (a) the date of notice of exercise of the Put (the
"Put Notification Date"), (b) the dollar amount of the equity investment
required to be made by Purchaser, (c) the Put Price Per Share (as defined in
Section 2.4 below), (d) the number of Put Shares to be purchased, (e) the date
on which the Purchaser shall purchase the Put Shares from the Company (the "Put
Date") and (f) a written statement of the calculation of the Put Price Per
Share. Such written notice shall be given by the Company within two (2) business
days after the Put Notification Date. The Put Date shall be no sooner than the
third business day nor later than the seventh business day after the Purchaser
receives such notice.

         2.3 Put Shares. With respect to each exercise of the Put, the "Put
Shares" shall be defined as that number of shares of Common Stock of the Company
as determined by dividing the dollar amount of the equity investment to be made
by the Purchaser by the Put Price Per Share; provided, however, that the
aggregate equity investment that the Purchaser shall be required to make
pursuant to this Agreement shall not exceed $5,000,000, with the number of Put
Shares determined in accordance with the applicable Put Price Per Share. For
example, if the Company partially exercises the Put and sells Put Shares to the
Purchaser valued at $2,000,000 based on the applicable Put Price Per Share, the
Company may, prior to the expiration of the Put Period, exercise the Put one
more time and sell Put Shares to the Purchaser valued at up to $3,000,000 (or
any lesser amount if greater than $1,000,000) based on the then applicable Put
Price Per Share.

         2.4 Put Price Per Share. The "Put Price Per Share" shall be defined as
the lesser of (a) the arithmetic average of the closing sales prices of the
Common Stock of the Company as reported by The Nasdaq National Market for the
twenty (20) consecutive days on which the Common Stock is traded prior to and
including the Put Notification Date, or (b) $7.00. The Put Price Per Share shall
be appropriately adjusted to reflect any stock dividend, stock split,
recapitalization or similar corporate action.

         2.5 Sale of the Put Shares. Subject to the terms and conditions hereof,
upon exercise by the Company of the Put, the Company hereby agrees to issue and
sell to the Purchaser, and the Purchaser hereby agrees to purchase from the
Company, the Put Shares for an aggregate purchase price not to exceed
$5,000,000.

         Section 3. Closing and Delivery.

         3.1 Initial Closing. Subject to the satisfaction or waiver of the
conditions to Initial Closing set forth in Sections 8 and 9 hereof, the initial
closing of this Agreement (the "Initial Closing") shall be held on October 1,
1998 at the offices of Dorsey & Whitney LLP, 220 South Sixth Street,
Minneapolis, Minnesota 55402, or on such other date and place as may be agreed
to by the Company and the Purchaser. The date upon which the Initial Closing
occurs is herein referred to as the "Initial Closing Date."

                                        2
<PAGE>
 
         3.2 Put Closing. Each closing of the purchase and sale of the Put
Shares pursuant to this Agreement (each, a "Put Closing") shall be held on the
Put Date at the offices of Dorsey & Whitney LLP, 220 South Sixth Street,
Minneapolis, Minnesota 55402, or on such other date and place as may be agreed
to by the Company and the Purchaser. The date upon which each Put Closing occurs
is herein referred to as the "Put Closing Date".

         3.3 Delivery of the Shares. At each Put Closing, the Company shall
deliver to the Purchaser an executed stock certificate registered in the name of
the Purchaser, or in such nominee name(s) as designated by the Purchaser,
representing the Put Shares purchased by the Purchaser. Also at each Put
Closing, the Purchaser shall pay to the Company the aggregate purchase price for
the Put Shares by certified check or wire transfer.

         Section 4. Representations and Warranties of the Company. Except as set
forth on the Schedule of Exceptions attached hereto as Exhibit A, the Company
hereby represents and warrants as of the date hereof to the Purchaser as
follows:

         4.1 Organization and Standing. Each of the Company and its Subsidiary
(as hereinafter defined in this Section 4.1) has been duly incorporated and is
validly existing as a corporation in good standing under the laws of the
jurisdiction of its organization, has full corporate power and authority to own
or lease its properties and conduct its business as presently conducted, and is
duly qualified as a foreign corporation and is in good standing in all
jurisdictions in which the character of the property owned or leased or the
nature of the business transacted by it makes qualification necessary (except
where the failure to be so qualified would not have a material adverse effect on
the business, properties, financial condition or results or operations of the
Company or its Subsidiary). Other than Diametrics Medical, Ltd., formerly known
as Biomedical Sensors, Ltd., (the "Subsidiary"), the Company has no subsidiaries
or equity interest in any other entity.

         4.2 Corporate Power; Authorization. The Company has all requisite
corporate power, and will have taken all requisite corporate action, to execute
and deliver this Agreement, to sell and issue the Put Shares and to carry out
and perform all of its obligations hereunder. This Agreement constitutes the
legal, valid and binding obligation of the Company, enforceable in accordance
with its terms, except (i) as limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws relating to or affecting the
enforcement of creditors' rights generally, (ii) as limited by equitable
principles generally, and (iii) as rights to indemnity or contributions
hereunder may be limited by federal or state securities laws or principles of
public policy. The execution and delivery of this Agreement, the performance of
this Agreement and the compliance with the provisions hereof do not, and the
issuance, sale and delivery of the Put Shares by the Company will not, conflict
with, or result in a breach or violation of the terms, conditions or provisions
of, or constitute a default under, or result in the creation or imposition of
any lien pursuant to the terms of, the Articles of Incorporation or Bylaws of
the Company or any statute, law, rule or regulation applicable to the Company or
its Subsidiary, or any state or federal order, judgment or decree applicable to
the Company or its Subsidiary, or any indenture,

                                        3
<PAGE>
 
mortgage, lease or other agreement or instrument to which the Company or its
Subsidiary or any of the properties of such person is subject, except such as
would not have a material adverse effect on the business, properties, financial
condition or results of operations of the Company or its Subsidiary.

         4.3 Issuance and Delivery of the Put Shares. The Put Shares, when
issued and paid for in compliance with the provisions of this Agreement, will be
validly issued, fully paid and nonassessable and issued in compliance with all
applicable federal and state securities laws. Further, the Put Shares, when
issued and paid for in compliance with the provisions of this Agreement, will
not be subject to preemptive, co-sale, right of first refusal or any other
similar rights of the shareholders of the Company or any liens or encumbrances.
Issuance of the Put Shares does not and will not constitute a default under or
give rise to a right of termination, cancellation, restriction or acceleration
of any right or obligation of the Company or its Subsidiary or a loss of any
benefit to which the Company or its Subsidiary is entitled under any provision
of any agreement, contract or other instrument binding upon or applicable to the
Company or its Subsidiary or any of the properties, assets, licenses,
franchises, permits or other similar authorizations of either of them.

         4.4 SEC Documents; Financial Statements. Each of the Company and its
Subsidiary has filed in a timely manner all documents that such person was
required to file with the Securities and Exchange Commission ("SEC") under
Sections 13, 14(a) and 15(d) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act") during the 36 months preceding the date of this Agreement.
As of their respective filing dates (or, if amended, when amended), all
documents filed by the Company or its Subsidiary with the SEC, whether under the
Exchange Act or under the Securities Act of 1933, as amended (the "Securities
Act"), during such 36-month period (the "SEC Documents") complied in all
material respects with the requirements of the Exchange Act or the Securities
Act, as the case may be. The Company satisfies the requirements for the use of
Form S-3 under the Securities Act, to register the offers and sales of the Put
Shares contemplated by the Shelf Registration Statement (as defined in Section
10). None of the SEC Documents as of their respective dates contained any untrue
statement of material fact or omitted to state a material fact required to be
stated therein or necessary to make the statements made therein, in light of the
circumstances under which they were made, not misleading. The consolidated
financial statements of the Company and its Subsidiary included in the SEC
Documents (the "Financial Statements") comply as to form in all material
respects with applicable accounting requirements and with the published rules
and regulations of the SEC with respect thereto. The Financial Statements have
been prepared in accordance with generally accepted accounting principles
consistently applied and fairly present the consolidated financial position of
the Company and its Subsidiary at the dates thereof and the results of their
operations and cash flows for the periods then ended (subject, in the case of
unaudited statements, to normal, recurring adjustments (unless otherwise
disclosed in the SEC Documents) and the absence of footnotes). There is no
material liability or commitment of the Company or its Subsidiary which is not
reflected in the most recent Financial Statements except commitments made since
the date of such Financial Statements in the ordinary course of

                                        4
<PAGE>
 
business. There have not been any changes in the assets, liabilities, financial
condition or operations of the Company or its Subsidiary from those reflected in
the most recent Financial Statements, except changes in the ordinary course of
business that have not had and are not reasonably expected to have a material
adverse effect on the business, properties, financial condition or results of
operations of the Company or its Subsidiary.

         4.5 Intellectual Property. (a) Each of the Company and its Subsidiary
has sufficient title and ownership of all material patents, patent rights,
inventions, trademarks, service marks, copyrights, trade secrets, proprietary
rights, processes and know-how (collectively, "Intellectual Property") owned or
used by it or that are necessary for the conduct of its business as presently
conducted and believes it can obtain, on commercially reasonable terms, any
additional rights necessary for its business as proposed to be conducted, and
the Intellectual Property does not, and will not, conflict with or constitute an
infringement of the rights of others;

         (b) There are no outstanding options, licenses (whether to or from the
Company) or agreements of any kind relating to the Intellectual Property
described in paragraph (a) of this Section 4.5 or granting rights to any other
person to manufacture, license, produce, assemble, market or sell products or
services derived or derivable from the Intellectual Property of the Company or
its Subsidiary, nor is the Company or its Subsidiary bound by or a party to any
options, licenses or agreements of any kind with respect to the Intellectual
Property of any other person or entity;

         (c) Neither the Company nor its Subsidiary has received any
communications alleging that such person or any of its employees has violated or
infringed or, by conducting its business as proposed, would violate or infringe,
any of the Intellectual Property of any other person or entity;

         (d) Neither the Company nor its Subsidiary is aware that any of its
employees is obligated under any contract (including licenses, covenants, or
commitments of any nature) or other agreement, or subject to any judgment,
decree, or order of any court or administrative agency, that would interfere
with the use of such employee's best efforts to promote the interests of the
Company or its Subsidiary with respect to the Intellectual Property of the
Company or its Subsidiary or otherwise or that would conflict with the business
of the Company or its Subsidiary as proposed to be conducted; and

         (e) Neither the execution nor delivery of this Agreement, nor the
carrying on of the business of the Company or its Subsidiary by the employees of
such person, nor the conduct of the business of the Company or its Subsidiary as
proposed, will, to the Company's knowledge, conflict with or result in a breach
of the terms, conditions, or provisions of, or constitute a default under, any
contract, covenant, or instrument under which any of such employees is now
obligated. The Company does not believe it is or will be necessary to utilize
any inventions of any of the employees of the Company or its Subsidiary (or
people such person currently intends to hire) made prior to their employment by
such person.

                                        5
<PAGE>
 
         4.6 Properties. The Company and its Subsidiary have good and valid
title to all of the properties and assets reflected as owned by the Company or
its Subsidiary in the Financial Statements, free and clear of all material
liens, mortgages (statutory or otherwise), security interests, pledges, claims
or encumbrances except those, if any, disclosed in the Financial Statements. The
Company and its Subsidiary hold their leased properties under valid and binding
leases, with such exceptions as are not materially significant in relation to
the business of the Company or its Subsidiary. The Company and its Subsidiary
own or lease all of such properties as are necessary to their operations as now
conducted.

         4.7 Capitalization. The authorized capital stock of the Company
consists of 35,000,000 shares of Common Stock and 5,000,000 shares of preferred
stock. There are 23,366,258 shares of Common Stock and no shares of Preferred
Stock outstanding as of the date of this Agreement, and, excluding the exercise
of vested options and warrants outstanding at the discretion of the holder
thereof and shares purchased through the Company's existing employee stock
purchase plan, immediately prior to the Initial Closing, 23,366,258 shares of
Common Stock and no shares of Preferred Stock will be outstanding. The
certificates evidencing the Put Shares will be in due and proper legal form and
will be duly authorized for issuance by the Company. All of the issued and
outstanding securities of the Company have been duly authorized and validly
issued, are fully paid and nonassessable, have been issued in compliance with
federal, state and other applicable laws and were issued without violation of
any preemptive, co-sale or other right. Except as otherwise disclosed in the SEC
Documents and in the Financial Statements, there is no outstanding option,
warrant, agreement or other right calling for the issuance or redemption of, and
there is no commitment, plan or arrangement to issue or redeem, any securities
of the Company. The Company does not have any binding agreement with respect to
the acquisition or purchase of the securities of or owned by any person or
entity or the acquisition of the business, assets or liabilities of any person
or entity, and the Company does not have any agreement or understanding with
respect to the disposition or sale of its business, or any of its material
assets or property.

         4.8 Litigation. There is no pending or, to the Company's knowledge,
threatened, action, suit or other proceeding to which the Company or its
Subsidiary is a party or to which the property or assets of the Company or its
Subsidiary is subject which might result in a material adverse effect on the
business, properties, financial condition or results of operations of the
Company or its Subsidiary.

         4.9 No Defaults. Neither the Company nor its Subsidiary is in violation
or default of any provisions of its Articles of Incorporation or Bylaws, or any
organizational documents, or in breach with respect to any provision of any
agreement, judgment, decree, order, mortgage, deed of trust, lease franchise,
license, indenture, permit or other instrument to which it is a party or by
which it or any of its properties are bound which violation, default or breach
would have a material adverse effect on the business, properties, financial
condition or results of operations of the Company or its Subsidiary, and there
does not exist any state of facts which constitutes an

                                        6
<PAGE>
 
event of default on the part of the Company or its Subsidiary as defined in such
documents or which, with notice or lapse of time or both, would constitute such
an event of default.

         4.10 Material Agreements. Each of the Company and its Subsidiary is a
party to all agreements that are necessary for the conduct of the business of
such person as presently conducted and all such agreements are currently in
effect. Neither the Company nor its Subsidiary is in breach of any provision of
any such agreement where such breach would have a material adverse effect on the
business, properties, financial condition or results of operations of the
Company or its Subsidiary.

         4.11 Governmental Consents; Compliance with Law. No consent, approval,
order or authorization of, or registration, qualification, designation,
declaration or filing with, any federal, state, or local governmental authority
on the part of the Company is required in connection with the consummation of
the transactions contemplated by this Agreement except for (i) the filing of a
Shelf Registration Statement and all amendments thereto with the SEC as
contemplated by Section 10.1 of this Agreement, (ii) any filings required by
state securities laws and (iii) if required, the filing of a notification and
report form under the United States Hart-Scott-Rodino Antitrust Improvements Act
of 1976, as amended (the "HSR Act"). Each of the Company and its Subsidiary is
conducting business in compliance in all material respects with all applicable
laws, rules and regulations of the jurisdictions in which it is conducting
business, including but not limited to, all applicable local, state and federal
environmental laws and regulations.

         4.12 Insurance. Each of the Company and its Subsidiary maintains
insurance of the types and in the amounts generally deemed adequate for its
business covering all risks customarily insured against, all of which insurance
is in full force and effect.

         4.13 Investment Company. The Company is not an "investment company"
within the meaning of the Investment Company Act of 1940, as amended.

         4.14 Taxes. Each of the Company and its Subsidiary has filed all
necessary federal, state, local, and foreign income and franchise tax returns
and has paid or accrued all taxes shown as due thereon except for such taxes as
are being contested in good faith, and the Company has no knowledge of any tax
deficiency which has been or might be asserted or threatened against the Company
or its Subsidiary which would have a material adverse effect on the business,
properties, financial condition or results of operations of the Company or its
Subsidiary.

         4.15 Listing. The Company's Common Stock is traded on The Nasdaq
National Market.

         4.16 Broker's Fee. Other than Lehman Brothers and Bay City Capital, the
Company represents that there are no brokers or finders entitled to compensation
by the Company or its Subsidiary in connection with any of the transactions
referred to or contemplated hereby, and

                                        7
<PAGE>
 
shall indemnify the Purchaser for any such fees for which the Company or its
Subsidiary is responsible.

         4.17 Disclosure. No representation or warranty of the Company contained
in this Agreement or in the Schedule of Exceptions or in any bring-down
certificate required to be delivered to the Purchaser at the Initial Closing,
contains or will contain any untrue statement of a material fact or omit to
state a material fact required to make the statements herein or therein not
misleading.

         Section 5. Representations and Warranties of the Purchaser. The
Purchaser hereby represents and warrants as of the date hereof to the Company as
follows:

         5.1 Investment Purposes. (a) The Purchaser acknowledges that the Put
Shares are being issued in reliance upon the exception from the registration
requirements of the Securities Act provided by Section 4(2) thereof and as such
the Put Shares will be "restricted securities" within the meaning of Rule 144.

         (b) The Purchaser will be acquiring the Put Shares pursuant to this
Agreement in the ordinary course of its business and for its own account for
investment only and with no present intention of distributing any of such Put
Shares or any arrangement or understanding with any other persons regarding the
distribution of such Put Shares except in each case as conforms with all
applicable requirements of the Securities Act, applicable blue sky laws and all
rules and regulations promulgated thereunder.

         (c) The Purchaser will not, directly or indirectly, offer, sell,
pledge, transfer or otherwise dispose of (or solicit any offers to buy, purchase
or otherwise acquire or take a pledge of) any of the securities purchased
hereunder except in compliance with the Securities Act, applicable blue sky
laws, and the rules and regulations promulgated thereunder.

         (d) The Purchaser has, in connection with its decision to acquire the
Put Shares, relied with respect to the Company and its affairs solely upon the
SEC Documents and the other information delivered to such Purchaser by the
Company as described in Sections 4.4 above and the representations and
warranties of the Company contained herein.

         (e) The Purchaser is an "accredited investor" within the meaning of
Rule 501 of Regulation D promulgated under the Securities Act.

         (f) The Purchaser has full right, power, authority and capacity to
enter into this Agreement and to consummate the transactions contemplated hereby
and has taken all necessary action to authorize the execution, delivery and
performance of this Agreement. Upon the execution and delivery of this Agreement
by the Purchaser, this Agreement shall constitute a valid and binding obligation
of the Purchaser, enforceable in accordance with its terms, except (i) as
limited by applicable bankruptcy, insolvency, reorganization, moratorium or
similar laws

                                        8
<PAGE>
 
relating to or affecting the enforcement of creditors' rights generally, (ii) as
limited by equitable principles generally, including any specific performance,
and (iii) as to those provisions of Section 10.3 relating to indemnity or
contribution.

         5.2 No Advice. The Purchaser understands that nothing in this Agreement
or any other materials presented to the Purchaser in connection with the
acquisition of the Put Shares constitutes legal, tax or investment advice to the
Purchaser. The Purchaser has consulted such legal, tax and investment advisors
as it, in its sole discretion, has deemed necessary or appropriate in connection
with its purchase of the Put Shares.

         5.3 Restriction on Transfer. The Purchaser understands that: (a) other
than to a person directly or indirectly controlling, controlled by, or in common
control with, the Purchaser (any such person, an "Affiliate"), the Put Shares
will not be transferable in the absence of a registration under the Securities
Act or an exemption therefrom or in the absence of compliance with any term of
this Agreement; (b) the Company may provide stop transfer instructions to its
transfer agent with respect to the Put Shares in order to enforce the
restrictions contained in this Section 5.3 and to confirm that the Purchaser has
complied with its obligations contained in Section 10.2 hereof; and (c) each
certificate representing Put Shares shall be in the name of the Purchaser and
shall bear substantially the following legends (in addition to any legends
required under applicable securities laws):

         "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN
         REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE
         "SECURITIES ACT"), OR REGISTERED OR QUALIFIED UNDER THE SECURITIES LAWS
         OF ANY STATE OR OTHER JURISDICTION, AND MAY ONLY BE SOLD, PLEDGED,
         TRANSFERRED OR OTHERWISE DISPOSED OF BY PURCHASER IF SUBSEQUENTLY
         REGISTERED UNDER THE SECURITIES ACT AND REGISTERED OR QUALIFIED UNDER
         ANY APPLICABLE STATE OR OTHER SECURITIES LAWS, UNLESS THE COMPANY
         DETERMINES THAT EXEMPTION FROM SUCH REGISTRATION REQUIREMENT IS
         AVAILABLE."

The legend contained in this Section 5.3 shall be removed from a stock
certificate immediately upon receipt by the Company's transfer agent of a
certificate substantially in the form of Appendix I attached hereto.
Notwithstanding the foregoing, such Put Shares must be held in certificated form
until such Put Shares have been sold in accordance with the provisions of
Appendix I attached hereto.

         5.4 Broker's Fee. The Purchaser represents that there are no brokers or
finders entitled to compensation by the Purchaser in connection with any of the
transactions referred to herein or contemplated hereby, and shall indemnify the
Company for any such fees for which the Purchaser is responsible.


                                        9
<PAGE>
 
         Section 6. Covenants of the Parties.

         6.1 Maintenance of Listing. During the Put Period and for so long as
the Company is obligated to keep in effect the Shelf Registration Statement
provided under Section 10 hereof, the Company will use its reasonable best
efforts to maintain its listing on The Nasdaq National Market or a national
securities exchange, as defined in the Exchange Act.

         6.2 Filings. The parties shall consult and fully cooperate with and
provide assistance to each other in preparing and filing as soon as practicable
all consents, approvals and authorizations necessary or advisable to be made or
obtained from any third party or governmental agency in order to consummate the
transactions contemplated hereby.

         6.3 Waiver of Right of Investment. Within thirty (30) days following
the Initial Closing or prior to the first Put Closing, whichever occurs first,
the Purchaser shall have received a certificate from a duly authorized officer
of the Company certifying that "Purchasers" (as defined in the Preferred Stock
Purchase Agreement dated January 30, 1997, between the Company and the
"Purchasers" listed on Schedule A thereto) representing 95% of the Preferred
Shares purchased under that Preferred Stock Purchase Agreement have waived such
"Purchasers'" rights to invest under Section 7.5 thereof, with respect to the
transactions contemplated by this Agreement (including without limitation the
issuance of the Put Shares).

         6.4 Publicity. Neither party hereto shall originate any publicity, news
release, or other announcement, written or oral, whether to the public press,
the trade, JJPI's or Diametrics's customers or otherwise, relating to this
Agreement, or to performance hereunder or the existence of an arrangement
between the parties without the prior written approval of the other party
hereto, except as may be required by law or the requirements of the National
Association of Securities Dealers, in which case the party proposing to issue
such press release or make such public statement shall use reasonable efforts to
consult in good faith with the other party before issuing any such press release
or making any such public statement.. In no event shall the Company attribute
any statement to JJDC or any of its Affiliates in any public statement without
the prior written consent of JJDC. The Company shall not use the name of JJPI or
any of its Affiliates for advertising or promotional purposes without the prior
written consent of JJPI.

         Section 7. Survival of Representations, Warranties and Agreements;
         Indemnification.

         7.1 Survival. Notwithstanding any investigation made by any party to
this Agreement, all covenants, agreements, representations and warranties made
by the Company and the Purchaser herein and in the certificates for the
securities delivered pursuant hereto shall survive the execution of this
Agreement, the delivery to the Purchaser of the certificates representing the
Put Shares and the payment thereof, until the first anniversary of the Initial
Closing Date, except for the representations set forth in Section 4.3 and 4.7,
which shall survive indefinitely, and the representations as to taxes set forth
in Section 4.14, which shall survive for

                                       10
<PAGE>
 
the period expiring ninety (90) days after the expiration of the period during
which a claim by the applicable taxing authority for a deficiency or other tax
adjustment would not be barred by the statute of limitations applicable to such
taxes (any such period an "Indemnity Period").

         7.2 Purchaser's Right to Indemnification. Subject to the provisions of
this Section 7, the Company hereby agrees to indemnify and hold harmless the
Purchaser and its employees, agents, directors, officers, equity holders,
successors, predecessors, assigns and affiliates (collectively, the "Purchaser
Indemnified Parties") from and against (i) any and all losses, obligations,
liabilities, damages, claims, deficiencies, costs and expenses (including, but
not limited to, the amount of any settlement entered into pursuant hereto and
all reasonable legal and other expenses incurred in connection with the
investigation, prosecution or defense of the matter but excluding consequential
damages) (collectively, "Claims"), which may be asserted against or sustained or
incurred by the Purchaser Indemnified Parties in connection with, arising out
of, or relating to (A) any breach or alleged breach of any of the
representations, warranties, agreements and covenants made by the Company herein
or in any certificate or other document delivered to any Purchaser Indemnified
Party by or on behalf of the Company in connection with this Agreement; or (B)
any false, incorrect or misleading representation or warranty made by or on
behalf of the Company herein or in any certificate or other document delivered
to any Purchaser Indemnified Party by or on behalf of the Company in connection
with this Agreement; and (ii) any and all costs and expenses (including, but not
limited to, reasonable legal expenses) incurred by any Purchaser Indemnified
Party in connection with the enforcement of its rights under this Agreement. No
claim for indemnification pursuant to this Section 7 may be commenced after the
relevant Indemnity Period; provided, however, that claims made within such
Indemnity Period shall survive to the extent of the Claim covered thereby until
such Claim is finally determined and, if applicable, paid. The parties to this
Agreement acknowledge that such indemnification provisions apply only with
respect to the Put Shares and the shares of Common Stock issued or issuable as
dividends on, or other distributions with respect to the Put Shares; and any
other security issued or issuable in exchange for, or in replacement of, the Put
Shares.

         7.3 Procedure for Claims.

                  (a) Promptly, but in any event within 10 days after obtaining
knowledge of any claim or demand which may give rise to, or could reasonably
give rise to, a claim for indemnification hereunder (an "Indemnification
Claim"), the Purchaser shall give written notice to the Company of such
Indemnification Claim ("Notice of Claim"). A Notice of Claim shall be given with
respect to all Indemnification Claims; provided, however, that the failure to
give a timely Notice of Claim to the Company shall not relieve the Company from
any liability that it may have to the Purchaser Indemnified Parties hereunder to
the extent that the Company is not prejudiced by such failure. The Notice of
Claim shall set forth the amount (or a reasonable estimate) of the loss, damage
or expense suffered, or which may be suffered, by the Purchaser Indemnified
Party as a result of such Indemnification Claim and the aggregate amount of all
Indemnification Claims to date and a brief description of the facts giving rise
to such

                                       11
<PAGE>
 
Indemnification Claim. The Purchaser shall furnish to the Company such
information (in reasonable detail) as the Purchaser may have with respect to
such Indemnification Claim (including copies of any summons, complaint or other
pleading which may have been served on it and any written claim, demand,
invoice, billing or other document evidencing or asserting the same).

                  (b) If the claim or demand set forth in the Notice of Claim is
a claim or demand asserted by a third party (a "Third Party Claim"), the Company
shall have fifteen days (or such shorter period (but not less than ten days) if
any answer or other response or filing with respect to the pleadings served by
the third party is required prior to the fifteenth day) after the date of
receipt by the Company of the Notice of Claim (the "Notice Date") to notify the
Purchaser in writing of the election by the Company to defend the Third Party
Claim on behalf of the Purchaser Indemnified Parties.

                  (c) If the Company elects to defend a Third Party Claim on
behalf of the Purchaser Indemnified Parties, the Purchaser shall make available
to the Company and its agents and representatives all records and other
materials in the Purchaser's possession which are reasonably required in the
defense of the Third Party Claim and the Company shall pay any expenses payable
in connection with the defense of the Third Party Claim as they are incurred
(whether incurred by the Purchaser or the Company).

                  (d) If the Company has assumed control of the defense, the
Company may contest or settle the Third Party Claim on such terms as the Company
may choose, provided, however, that the Company will not have the right, without
the prior written consent of the Purchaser, to settle any such claim if such
settlement (i) arises from or is part of any criminal action, suit or proceeding
(ii) contains a stipulation to, confession of judgment with respect to, or
admission or acknowledgment of, any liability or wrongdoing on the part of any
Purchaser Indemnified Party, (iii) relates to any foreign federal, state or
local tax matters, (iv) provides for injunctive relief, or other relief other
than damages, which is binding on any Purchaser Indemnified Party, (v) does not
fully release all Purchaser Indemnified Parties with respect to the relevant
Third Party Claim or (vi) has any res judicata or collateral estoppel effect
that could be adverse to any Purchaser Indemnified Party.

                  (e) If the Company elects to defend a Third Party Claim, the
Purchaser Indemnified Parties shall have the right to participate in the defense
of the Third Party Claim, at the Purchaser Indemnified Parties' expense (and
without the right to indemnification for such expense under this Agreement);
provided, however, that the reasonable fees and expenses of counsel retained by
the Purchaser Indemnified Parties shall be at the expense of the Company if (A)
the use of the counsel chosen by the Company to represent the Purchaser
Indemnified Parties would present such counsel with a conflict of interest; (B)
the parties to such proceeding include both Purchaser Indemnified Parties and
the Company and there may be legal defenses available to Purchaser Indemnified
Parties which are different from or additional to those available to the
Company; (C) within ten days after being advised by the Company of the identity
of counsel to

                                       12
<PAGE>
 
be retained to represent the Purchaser Indemnified Parties, the Purchaser
Indemnified Party affected by such claim shall have objected to the retention of
such counsel for valid reasons (which shall be stated in a written notice to the
Company), and the Company shall not have retained different counsel reasonably
satisfactory to such Purchaser Indemnified Party; or (iv) the Company shall
authorize the Purchaser Indemnified Parties to retain separate counsel at the
expense of the Company.

                  (f) If the Company elects to defend a Third Party Claim, and
does not defend a Third Party Claim in good faith, the Purchaser Indemnified
Parties shall have the right, in addition to any other right or remedy it may
have hereunder, at the sole and exclusive expense of the Company, to defend such
Third Party Claim; provided, however, that such expenses shall be payable by the
Company only if and when such Third Party Claim becomes payable.

                  (g) The Purchaser shall cooperate with the Company in the
defense of Third Party Claims. Subject to the foregoing, (i) the Purchaser
Indemnified Parties shall not have any obligation to participate in the defense
of or to defend any Third Party Claim and (ii) the Purchaser Indemnified
Parties' defense of or participation in the defense of any Third Party Claim
shall not in any way diminish or lessen the right to indemnification as provided
in this Section 7.

         Section 8. Conditions to Company's Obligations at the Initial Closing.
The Company's obligation to complete the transactions contemplated by this
Agreement shall be subject to the satisfaction of the following conditions at
the Initial Closing to the extent not waived by the Company:

         8.1 Consents and Approvals. Any consents, waivers, clearances,
approvals and authorizations of regulatory or governmental bodies (including,
without limitation, the expiration or termination of the waiting period under
the HSR Act) and other persons that are necessary in connection with the
consummation of the transactions contemplated by this Agreement shall have been
obtained.

         8.2 Representations and Warranties Correct. The representations and
warranties made by the Purchaser in Section 5 hereof shall be true and correct
in all material respects when made, and shall be true and correct in all
material respects on the Initial Closing Date.

         Section 9. Conditions to the Purchaser's Obligations at the Initial
Closing. The Purchaser's obligation to complete the transactions contemplated by
this Agreement shall be subject to the satisfaction of the following conditions
at the Initial Closing to the extent not waived by the Purchaser:

         9.1 Consents and Approvals. Any consents, waivers, clearances,
approvals and authorizations of regulatory or governmental bodies (including,
without limitation, the expiration or termination of the waiting period under
the HSR Act) and other persons that are necessary in

                                       13
<PAGE>
 
connection with the consummation of the transactions contemplated by this
Agreement shall have been obtained.

         9.2 Representations and Warranties Correct. The representations and
warranties made by the Company in Section 4 shall be true and correct in all
material respects (except with respect to representations and warranties that
are qualified as to materiality or material adverse effect, which
representations and warranties shall be true and correct in all respects) when
made and as of the Initial Closing Date, and the Purchaser shall have received a
certificate signed by the chief executive officer of the Company, or such other
officers of the Company as agreed upon by the parties hereto, that each of such
representations and warranties is true and correct in all material respects
(except with respect to representations and warranties that are qualified as to
materiality or material adverse effect, which representations and warranties
shall be true and correct in all respects) on and as of the Initial Closing Date
with the same effect as though such representations and warranties had been made
or given on and as of the Initial Closing Date, and that such party has
performed and complied with all of its obligations under this Agreement which
are to be performed or complied with on or prior to the Initial Closing Date.

         9.3 Certificate as to Absence of Material Adverse Effect. The Purchaser
shall have received a certificate signed by a duly authorized officer of the
Company certifying that, since the date of the Company's most recent filing with
the SEC, there have not been any changes in the assets, liabilities, financial
condition or operations of the Company or its Subsidiary, except changes in the
ordinary course of business that have not had and are not expected to have a
material adverse effect on the business, properties, financial condition or
results of operations of the Company or its Subsidiary.

         9.4 Legal Opinion. The Purchaser shall have received from Dorsey &
Whitney LLP, counsel to the Company, an opinion letter addressed to the
Purchaser, dated as of the Initial Closing Date, covering the matters set forth
in Exhibit B hereto, subject to customary assumptions and qualifications.

         9.5 Closing Papers. The Purchaser shall have received the following,
addressed to Purchaser and in form and substance reasonably satisfactory to
Purchaser:

         (a) certified copies of the resolutions adopted by the Board of
Directors of the Company authorizing the execution, delivery and performance of
this Agreement, the issuance of the Put Shares and each of the other agreements,
instruments and transactions contemplated hereby;

         (b) certified copies of the certificate of incorporation and Bylaws of
the Company as in effect on the Initial Closing Date; and


                                       14
<PAGE>
 
         (c) a certificate of the Secretary of the Company dated the Initial
Closing Date, as to the incumbency and signatures of the officers executing this
Agreement and all instruments executed pursuant hereto.

         Section 10. Conditions to the Purchaser's Obligations at each Put
Closing. The Purchaser's obligations to complete the transaction contemplated by
this Agreement at each Put Closing shall be subject to the satisfaction of the
following conditions:

         10.1 Certificate regarding Representations and Warranties. The
Purchaser shall have received a certificate signed by the chief executive
officer of the Company, or such other officers of the Company as agreed upon by
the parties hereto, certifying that each of the representations and warranties
set forth in the form of officer certificate attached hereto as Exhibit C is
true and correct in all material respects (except with respect to
representations and warranties that are qualified as to materiality or material
adverse effect, which representations and warranties shall be true and correct
in all respects) on and as of the applicable Put Closing Date, and that the
Company has performed and complied with all of its obligations under this
Agreement which are to be performed and complied with on or prior to the
applicable Put Closing Date.

         10.2 Certificate as to Absence of Material Adverse Effect. The
Purchaser shall have received a certificate signed by a duly authorized officer
of the Company certifying that, except as otherwise set forth in documents filed
with the SEC, or in other publicly available documents, since the date of the
Company's most recent filing with the SEC, there have not been any changes in
the assets, liabilities, financial condition or operations of the Company or its
Subsidiary, except changes in the ordinary course of business that have not had
and are not expected to have a material adverse effect on the business,
properties, financial condition.

         10.3 Distribution Agreement. The Distribution Agreement (as amended
through the date of the applicable Put Closing, if applicable) shall continue to
be in full force and effect as of the applicable Put Closing Date, unless such
Distribution Agreement has been terminated as a result of a breach of such
Distribution Agreement by JJPI.

         Section 11. Registration of the Put Shares; Compliance with the
         Securities Act.

         11.1 Registration Procedures and Expenses. (a) Upon written demand of
the Purchaser received by the Company prior to one year following the final Put
Closing Date, the Company shall prepare and file with the SEC within sixty (60)
days following the receipt of such written demand, and thereafter shall use its
reasonable best efforts to cause to be declared effective, a shelf registration
statement on an appropriate form under the Securities Act relating to the offer
and sale of the Put Shares (the "Registrable Securities") by the Purchaser, in
accordance with the methods of distribution set forth in such shelf registration
statement, through The Nasdaq National Market or the facilities of any national
securities exchange on which the Company's Common Stock is then traded, or in
privately-negotiated transactions (a "Shelf

                                       15
<PAGE>
 
Registration Statement"). All shares of Common Stock acquired by the Purchaser
pursuant to Section 2 shall be included in such Shelf Registration Statement,
and the Company shall only be required to file up to two Shelf Registration
Statements with respect to the Put Shares.

         (b) The Company shall use its reasonable best efforts (including,
without limitation, the preparation and filing with the SEC of amendments and
supplements to the Shelf Registration Statement and a prospectus to be used in
connection therewith) to keep the Shelf Registration Statement continuously
effective and not misleading until the earlier of (i) such time as all of the
Registrable Securities have become eligible for sale under Rule 144 under the
Securities Act or (ii) when all the Registrable Securities covered by the Shelf
Registration Statement have been sold pursuant thereto. The Company shall be
deemed not to have used its reasonable best efforts to keep the Shelf
Registration Statement effective during the requisite period if it takes any
action that would result in the holders of the Registrable Securities covered
thereby not being able to offer and sell such Registrable Securities during that
period, unless such action is required by applicable law. Notwithstanding the
foregoing, following the effectiveness of the Shelf Registration Statement, the
Company may, at any time, suspend the effectiveness of the Shelf Registration
Statement for up to no longer than seventy-five (75) days, as appropriate (a
"Suspension Period"), by giving notice to the Purchaser, if (i) the Company
shall have determined that the Company may be required to disclose any material
corporate development or (ii) the Company shall be involved in an underwritten
public offering of its securities. The Company will use its best efforts to
minimize the length of any Suspension Period. Notwithstanding the foregoing, no
more than two Suspension Periods may occur in any twelve (12) month period. The
Purchaser agrees that, upon receipt of any notice from the Company of a
Suspension Period, it will not sell (subject to the limitations on the Company
set forth above) any Registrable Securities pursuant to the Shelf Registration
Statement until (i) the Purchaser is advised in writing by the Company that the
use of the applicable prospectus may be resumed, (ii) the Purchaser has received
copies of any additional or supplemental or amended prospectus, if applicable,
and (iii) the Purchaser has received copies of any additional or supplemental
filings which are incorporated or deemed to be incorporated by reference in such
prospectus.

         (c) In order to facilitate the public sale or other disposition of all
or any of the Registrable Securities by the Purchaser, the Company shall furnish
to the Purchaser with respect to the Registrable Securities registered under the
Shelf Registration Statement such number of copies of prospectuses, prospectus
supplements and preliminary prospectuses as the Purchaser reasonably requests in
conformity with the requirements of the Securities Act.

         (d) The Company shall file any documents required of the Company for
normal blue sky clearance in states specified in writing by the Purchaser;
provided, however, that the Company shall not be required to qualify to do
business or consent to service of process in any jurisdiction in which it is not
now so qualified or has not so consented.

         (e) Other than fees and expenses, if any, of counsel or other advisers
to the Purchaser, which fees and expenses shall be borne by them, the Company
shall bear all expenses

                                       16
<PAGE>
 
(exclusive of any brokerage fees, underwriting discounts and commissions) in
connection with the procedures in paragraphs (a) through (d) of this Section
11.1.

         11.2 Transfer of Securities After Shelf Registration. The Purchaser
agrees that it will not effect any disposition of the Registrable Securities
that would constitute a sale within the meaning of the Securities Act, except:

         (a) pursuant to the Shelf Registration Statement, in which case the
Purchaser shall submit the certificates evidencing the Registrable Securities to
the Company's transfer agent, accompanied by a separate "Purchaser's
Certificate" (A) in the form of Appendix I attached hereto, (B) executed by an
officer of, or other authorized person designated by, the Purchaser, and (C) to
the effect that (1) the Registrable Securities have been sold in accordance with
the Shelf Registration Statement and (2) the requirement of delivering a current
prospectus has been satisfied; or

         (b) in a transaction exempt from registration under the Securities Act.

         11.3 Indemnification in Connection with Registration. As used in this
Section 11.3 the following terms shall have the following respective meanings:

         (a) "Selling Shareholder" shall mean the Purchaser and any transferee
who is entitled to resell Registrable Securities pursuant to the Shelf
Registration Statement, including any underwriter involved in such resale, and
each person, if any, who controls such Selling Shareholder within the meaning of
Section 15 of the Securities Act, and each officer and each director of such
Selling Shareholder;

         (b) "Shelf Registration Statement" shall include any final prospectus,
exhibit, supplement or amendment included in or relating to the Shelf
Registration Statement referred to in Section 10.1; and

         (c) "Untrue Statement" shall include any untrue statement or alleged
untrue statement, or any omission or alleged omission to state in the Shelf
Registration Statement a material fact required to be stated therein or
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading.

         The Company agrees to indemnify and hold harmless each Selling
Shareholder from and against any losses, claims, damages or liabilities to which
such Selling Shareholder may become subject (under the Securities Act or
otherwise) insofar as such losses, claims, damages or liabilities (or actions or
proceedings in respect thereof) arise out of, or are based upon, any Untrue
Statement on or after the effective date of the Shelf Registration Statement, or
on or after the date of any prospectus or prospectus supplement or the date of
any sale by any purchaser thereunder, or arise out of any failure by the Company
to fulfill any undertaking included in the Shelf Registration Statement and the
Company will reimburse such Selling

                                       17
<PAGE>
 
Shareholder for any reasonable legal or other expenses reasonably incurred in
investigating, defending or preparing to defend any such action, proceeding or
claim; provided, however, that the Company shall not be liable to such Selling
Shareholder in any such case to the extent that such loss, claim, damage or
liability arises out of, or is based upon, an Untrue Statement made in such
Shelf Registration Statement in reliance upon and in conformity with written
information furnished to the Company by or on behalf of such Selling Shareholder
specifically for use in preparation of the Shelf Registration Statement, or the
failure of such Selling Shareholder to comply with the covenants and agreements
contained in Section 11.1 or 11.2 hereof respecting sale of the Registrable
Securities or any statement or omission in any prospectus that is corrected in
any subsequent prospectus that was delivered to the Selling Shareholder prior to
the pertinent sale or sales by the Selling Shareholder.

         The Purchaser agrees to indemnify and hold harmless the Company (and
each person, if any, who controls the Company within the meaning of Section 15
of the Securities Act, each officer of the Company who signs the Shelf
Registration Statement and each director of the Company) from and against any
losses, claims, damages or liabilities to which the Company (or any the officer,
director or controlling person) may become subject (under the Securities Act or
otherwise), insofar as such losses, claims, damages or liabilities (or actions
or proceedings in respect thereof) arise out of, or are based upon, the failure
by the Purchaser to comply with the covenants and agreements contained in
Section 11.1 or 11.2 hereof respecting sale of the Registrable Securities, or
any Untrue Statement contained in the Shelf Registration Statement on or after
the effective date thereof, or in any prospectus supplement as of its issue date
or date of any sale by the Purchaser thereunder, if such Untrue Statement was
made in reliance upon and in conformity with written information furnished by or
on behalf of the Purchaser specifically for use in preparation of the Shelf
Registration Statement, and the Purchaser will reimburse the Company (or such
officer, director or controlling person), as the case may be, for any legal or
other expenses reasonably incurred in investigating, defending or preparing to
defend any such action, proceeding or claim; provided that in no event shall any
indemnity by the Purchaser under this Section 11.3 exceed the gross proceeds
received by the Purchaser from the sale of Registrable Securities covered by
such Shelf Registration Statement.

         Promptly after receipt by any indemnified person of a notice of a claim
or the beginning of any action in respect of which indemnity is to be sought
against an indemnifying person pursuant to this Section 11.3, such indemnified
person shall notify the indemnifying person in writing of such claim or of the
commencement of such action, and, subject to the provisions hereinafter stated,
in case any such action shall be brought against an indemnified person and such
indemnifying person shall have been notified thereof, such indemnifying person
shall be entitled to participate therein, and, to the extent it shall wish, to
assume the defense thereof, with counsel reasonably satisfactory to such
indemnified person. After notice from the indemnifying person to such
indemnified person of its election to assume the defense thereof, such
indemnifying person shall not be liable to such indemnified person for any legal
expenses subsequently incurred by such indemnified person in connection with the
defense thereof; provided, however, that if there exists or shall exist a
conflict of interest that would make it

                                       18
<PAGE>
 
inappropriate, in the opinion of counsel to the indemnified person, for the same
counsel to represent both the indemnified person and such indemnifying person or
any affiliate or associate thereof, the indemnified person shall be entitled to
retain its own counsel at the expense of such indemnifying person; provided,
however, that no indemnifying person shall be responsible for the fees and
expenses of more than one separate counsel for all indemnified parties.

         11.4 Termination of Conditions and Obligations. The conditions
precedent imposed by Section 5 or this Section 11 upon the transferability of
the Registrable Securities shall cease and terminate as to any particular number
of the Registrable Securities when such Registrable Securities shall have been
sold or otherwise disposed of in accordance with the intended method of
disposition set forth in the Shelf Registration Statement covering such
Registrable Securities or at such time as an opinion of counsel satisfactory to
the Company shall have been rendered to the effect that such conditions are not
necessary in order to comply with the Securities Act.

         11.5 Information Available. So long as the Purchaser continues to own
any of the Registrable Securities and the Shelf Registration Statement is
effective covering the resale of Registrable Securities owned by such person,
the Company will make available to each such person:

         (a) as soon as practicable after available (but in the case of the
Company's Annual Report to Shareholders, within one hundred twenty (120) days
after the end of each fiscal year of the Company), one copy of (i) its Annual
Report to Shareholders (which Annual Report shall contain financial statements
audited in accordance with generally accepted auditing standards certified by a
national firm of certified public accountants); (ii) its Annual Report on Form
10-K (excluding exhibits); (iii) its quarterly reports on Form 10-Q (excluding
exhibits); (iv) its Proxy Statement; and (v) its current reports on Form 8-K, if
any (excluding exhibits);

         (b) upon the request of any such person, all exhibits excluded by the
parentheticals to subparagraphs (a)(ii),(iii) and (v) of this Section 11.5, in
the form generally available to the public; and

         (c) upon the reasonable request of any such person, an adequate number
of copies of the prospectuses and supplements to supply to any other party
requiring such prospectuses.

         11.6 Changes in Information. The Purchaser agrees to promptly notify
the Company of any changes in the information set forth in the Shelf
Registration Statement regarding such person or such person's plan of
distribution set forth in such Shelf Registration Statement.

         Section 12. Notices.

         All notices, requests, consents and other communications hereunder
shall be in writing, shall be sent by confirmed facsimile or mailed by
first-class registered or certified airmail, or

                                       19
<PAGE>
 
nationally recognized overnight express courier, postage prepaid, and shall be
deemed given when so sent in the case of facsimile transmission, or when so
received in the case of mail or courier, and addressed as follows:

         (a)      if to the Company, to:

                  Diametrics Medical, Inc.
                  2658 Patton Road
                  Roseville, Minnesota  55113
                  Attention: David T. Giddings, Chairman, CEO and President
                  Phone: (612) 639-8035
                  Fax: (612) 638-1197

         with a copy to:

                  Dorsey & Whitney LLP
                  220 South 6th Street
                  Minneapolis, Minnesota  55402
                  Attention: Kenneth Cutler, Esq.
                  Phone: (612) 340-2740
                  Fax: (612) 340-8738

         (b)      if to the Purchaser, to:

                  Johnson & Johnson Development Corporation
                  One Johnson & Johnson Plaza
                  New Brunswick, New Jersey 08933
                  Attention: Tom Gorrie
                  Phone: (732) 524-6730
                  Fax: (732) 524-5310

         with a copy to:

                  Johnson & Johnson, Inc.
                  Office of General Counsel
                  One Johnson & Johnson Plaza
                  New Brunswick, New Jersey 08933
                  Attention: General Counsel
                  Phone: (732) 524-0400
                  Fax: (732) 524-2788

Any change of an address set forth in this Section 12 may be accomplished by
means of a notice sent in accordance with the terms of this Section 12.

                                       20
<PAGE>
 
         Section 13. Miscellaneous.

         13.1 Waivers and Amendments. Neither this Agreement nor any provision
hereof may be changed, waived, discharged, terminated, modified or amended
except upon the written consent of the Company and the Purchaser.

         13.2 Sections; Headings; Dollar Amounts. Unless otherwise specified,
all references in this Agreement to "Sections" shall be to Sections of this
Agreement. The headings of the various sections of this Agreement have been
inserted for convenience of reference only and shall not be deemed to be part of
this Agreement. All currency referred to herein shall be in U.S.
dollars.

         13.3 Severability. In case any provision contained in this Agreement
should be invalid, illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions contained herein shall
not in any way be affected or impaired thereby.

         13.4 Governing Law. This Agreement shall be governed by and construed
in accordance with the laws of the State of Minnesota as applied to contracts
entered into and performed entirely in Minnesota by Minnesota residents, without
regard to conflicts of law principles.

         13.5 Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall constitute an original, but all of which, when
taken together, shall constitute but one instrument, and shall become effective
when one or more counterparts have been signed by each party hereto and
delivered to the other parties. Delivery of an executed counterpart by facsimile
shall be the same as delivery of an original counterpart.

         13.6 Successors and Assigns. Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors and administrators of the
parties hereto.

         13.7 Entire Agreement. This Agreement and other documents delivered
pursuant hereto, including the exhibits, constitute the full and entire
understanding and agreement between the parties with regard to the subjects
hereof and thereof.

         13.8 Payment of Fees and Expenses. Each of the Company and the
Purchaser shall bear its own expenses and legal fees incurred on its behalf with
respect to this Agreement and the transactions contemplated hereby. If any
action at law or in equity is necessary to enforce or interpret the terms of
this Agreement, the prevailing party shall be entitled to reasonable attorney's
fees, costs and necessary disbursements in addition to any other relief to which
such party may be entitled.

                                    * * * * *

                                       21
<PAGE>
 
         In Witness Whereof, the parties hereto have caused this Agreement to be
executed by their duly authorized representatives as of the day and year first
above written.

                                         DIAMETRICS MEDICAL, INC.


                                         By:    /s/ David T. Giddings
                                                ------------------------- 
                                         Name:  David T. Giddings
                                         Title: Chairman, President & CEO


                                         JOHNSON & JOHNSON DEVELOPMENT
                                              CORPORATION


                                         By:    /s/ Thomas M. Gorrie     
                                                -------------------------
                                         Name:  Thomas M. Gorrie
                                         Title: Vice President



                                       22
<PAGE>
 
                                                                      APPENDIX I

                            DIAMETRICS MEDICAL, INC.

                 PURCHASER'S CERTIFICATE OF RESALE OF THE SHARES

         (i) The undersigned, an officer of, or other person duly authorized by

-------------------------------------------------------------------------------
              [fill in official name of individual or institution]

hereby certifies that he/she [said institution] is the Purchaser of the Shares
evidenced by the attached stock certificate(s) and as such, sold such Shares on
__________________ in accordance with shelf registration statement number

--------------------------------------------------------------------------------
   [fill in the number of or otherwise identify shelf registration statement]

and the requirement of delivering a current prospectus and current annual,
quarterly and current reports (Forms 10-K, 10-Q and 8-K) by the Company has been
complied with in connection with such sale.

Print or Type:
     
Name of Purchaser:                                                       
                                                --------------------------------
Name of Individual representing Purchaser:                               
                                                --------------------------------

Title of Individual representing Purchaser:                              
                                                --------------------------------

Signature by:

Individual representing Purchaser:                                        
                                                --------------------------------


                                       23
<PAGE>
 
                                                                       EXHIBIT A


                                                        [Schedule of Exceptions]







                                       24
<PAGE>
 
                                                                       EXHIBIT B


                                                         [Form of Legal Opinion]












                                                       25
<PAGE>
 
                                                                       EXHIBIT C


                                                   [Form of Officer Certificate]












                                       26