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Grade of written test: Final grade: Grade of project: Signature: Technologies for Sensors and Clinical Instrumentation 3 July 2015 FAMILY NAME ……………………….… NAME ….…………………. MATR ………… PREFERENCE for ORAL: † 9 July (morning) † 9 July (afternoon) † 10 July (morning) † 10 July (morning) † next calls Notes: - Answers are considered complete only if units of measurement are indicated. - Only answers on this sheets are considered for evaluation. - Questions are independent from each other. Q.1) (8 points) A temperature sensor catheter is designed for thermo-dilution measurements. The adopted sensor is a thermistor, which characteristic ሻ is represented by the following expression: ܴ଴݁ ఉሺଵ ்ିଵ ்బ ሻ ܴ଴ (equal to Ω݇is the thermistor resistance at ambient temperature ܶ଴ܭand ߚis the material constant of the thermistor (equal to 4000 K). The thermistor has a dissipation coefficient ߜ in blood equal to ܭ/ܹ݉ . The conditioning circuit consists of a Wheatstone bridge (1/4 bridge). The circuit is modified by shunting the sensor ݐܴwith a resistor ݌ܴin order to linearize the measurements around the body temperature ܶ௕ܭ . 1 - 1.a) The parallel resistor value is chosen according to the following formula: ்ܴሺܶ௕ሻ∙ ఉିଶ்್ ఉାଶ்್ . Explain how this formula can be obtained (computations are not required). Compute the value of ݌ܴ . …………………………………………………………… ..……………………………………………………………………………………………………… ..……………………………………………………………………………………………………… ..……………………………………………………………………………………………………… ..……………………………………………………………………………………………………… 2 - 1.b) The “shunted” sensor ܴ// ൌ ோ௣ோ௧ ோ௣ାோ௧ can be assumed to have a linear response to ሺܾܶሻ: ܴ// ܴ// ்್ ∙ሺ 1൅ ௗோ// ௗ்|்ୀ்್ ∙ ଵ ோ//೅್ ܶ௕ܴ// ்್ ܶ௕ሻሻ. Show that ൌെ 0 . 0 1 8 Ω Ω ܭିଵ. ……………………………………………………………………………………………………….. ………………………………………………………………………………………………………..…