Question

Now you know the circuit in Problem 1 is a differential amplifier. You prepared a Wheatstone bridge circuit with 4 strain gauges (R1-R2-R3 R4 100 2, AR1- AR4, AR2- AR3) for measuring mechanical property of a cantilever beam. You are expecting the differential amplifier will amplify _1'a, with a gain A of the differential amplifier. 50042 Cr 1 00Ω 1002 5002 R2, Rs bonded to bottom surface Differential Amplifier Strain gauges Wheatstone Bridge (1) Determine va and vb of the bridge without connection to a differential amplifier. (2) After connecting to differential amplifier, determine 1, with variable l'a and 1ъ obtained in (1). Is 1,0 in the form of Ά(M-1, )'? If it isn't explain why. (3) It seems you need impedance isolation between the Wheatstone bridge transducer and the differential amplifier. Suggest a proper differential amplifier guaranteeing isolation of impedance between the transducer and the amplifier (Hint: page 467-474 of the textbook.)

Answer 1

Us Ri 4R,482 R3tRy RitR 10o 00 +H100 500 oon LOo oon At hode 0 At node 2 500 i oo 100 5 6 5

isolation ,VIAず 下. -In optcal Couplihą me ho d for ampl:fer Isolatton.