Question

5. (20 points) We use strain gauge to create a fish weight scale. The strain gauges are mounted on a plastic tube with fish hanging on to it. The strain gauges have resistance R 2400 2 (unstrained) and the GF 2.14. A (1) Which is the dummy gauge, A or B? Circle the dummy gauge. (2) Show how to wire the two gauges and two fixed 2400 Ω resistors into the bridge circuit to provide temperature compensation, using the graphs given on the right Assume the plastic tube has an outer diameter of 3 cm and an inner diameter of 2 cm and its modulus of elasticity is E 3.45 x 10 N/m2. If the weight of the fish is given by Newton's Law: F mg, where g- 9.8 m/s and m is the mass in kilograms. B s v (3) What is the strain produced by a fish of 5 kg? (4) How much resistance change will result from this strain? What will be the bridge off-null voltage for this strain? (5) Find the gain and show the circuit of a differential amplifier so that a 5 kg fish wll provide an output of 2.0 v. Show how the bridge is connected to the amplifier inputs.

Answer 1

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