1 March 1, 2000 Thermedics Inc. 470 Wildwood Street Woburn, MA 01888 Attn: John Keiser Dear Jack: Reference is made to Thermedics Inc.'s proposed acquisitions of the minority interest investment in each of its majority owned subsidiaries, Thermo Sentron Inc. and Thermedics Detection Inc. In connection with those transactions, Thermo Electron Corporation intends to loan Thermedics up to $20,000,000 for the acquisition of such interests in each of Thermo Sentron and Thermedics Detection. This loan will be available at an interest rate equal to the 30-day Dealer Commercial Paper Rate plus 150 basis points, set at the beginning of each month, provided such rate shall be reduced to the Dealer Commercial Paper Rate plus 50 basis points to the extent of any funds invested by Thermedics' majority owned subsidiaries in Thermo Electron's cash management arrangement. Interest will be due and payable on a monthly basis and the loan will be payable in full on September 1, 2000. If these terms are acceptable to you, please sign the letter as indicated below to evidence your acceptance of the terms. Sincerely, THERMO ELECTRON CORPORATION /s/Theo Melas-Kyriazi Theo Melas-Kyriazi Vice President and Chief Financial Officer ACCEPTED AND AGREED TO: THERMEDICS INC. John T. Keiser /s/John T. Keiser President and CEO