Pergamon Mechatronics Vol. 6, No. 8, pp. 855-866, 1996 Copyright © 1996 Elsevier Science Ltd. All rights reserved. Printed in Great Britain. 0957-4158/96 $15.00+0.00 PII: S0957-4158 (96) 00031-1 FREQUENCY TRANSFER FUNCTION OF AN OPTO-PNEUMATIC DETECTOR G. BELFORTE,* T. RAPARELLI,* V. VIKTOROV,* G. EULA* and A. IVANOV* *Department of Mechanics, Politecnico di Torino C.so Duca degli Abruzzi 24, 1012 Torino, Italy and tDepartment of Energetics, Universith di L'Aquila 67040 Roio Pog L'Aquila, Italy (Received 26 May 1996; accepted 4 July 1996) Abstract--An example of an opto-pneumatic detector's (OPD) frequency trans- fer function is presented for the development of an opto-pneumatic interface. The theoretical model is tested through experiments in the laboratory on a rea OPD prototype. In this way many of the model's parameters are studied and evaluated, such as the dimensions of the gas chamber, the thickness of the absorbent body, and the load of the OPD. The results obtained are good and show the utility of the studies described here. Copyright (~) 1996 Elsevier Science Ltd. NOMENCLATURE C thermal capacitance Cp specific heat at constant pressure F impulse frequency G fluid conductance L length L' effective length M mass p pressure Q volume flow rate q power of the optic signal qs surface signal power R thermal resistance R ° gas constant T time constant T ° temperature t time r chamber radius S surface area V volume thermal conductivity 855