Instrumentation

EXAM NUMBER 1 SPRING 2000 NAME:________________________

1). For the circuit shown below: (18 pts.)

a). What is the value of the time constant?

b). What is the value of the voltage across the capacitor at time, t = 3 s?

c). What is the current in the circuit at time, t = 0.5 s?

2. A. (24 pts) Say you wanted the MOST voltage output from a Wheatstone bridge. Show on the aluminum plate below, how you would place the strain gage(s) (please number it (or them)), then sketch a Wheatstone bridge circuit and show where the gage (s) is (are) should be placed in the circuit. Indicate whether it (or they) are in tension or compression. Also indicate Vo and V on your circuit. (Arrows indicate applied stress to the sample)

B. (10 pts.) If the gages are 120 ohms (gage factor = 2.05), excitation voltage = 10 volts, and the induced strain in the vertical direction is 2000 microstrain, what will the output voltage be? Poisson's ratio for aluminum is 0.28

3. (8 pts) What is the voltage output from a quarter bridge that has a shunt resistor inserted into it? Excitation voltage is 5 V, 350 ohm resistors, shunt resistor is 59K ohms.

4. (30 pts) What is the total power consumed by this circuit?

What is Vth and Rth at the 120 ohm resistor?

What is the voltage drop and current thru the 120 ohm resistor?