# Homework Help: Measuring device used for a stressed crystal microphone

1. Nov 24, 2008

### physicsgoon

1. The problem statement, all variables and given/known data

Choose an instrument to measure the output from the crystal, when measuring variations in stress. The maximum voltage from the crystal is 200mV. current in circuit is 2 x 10-8 A, p.d is 4 x 10-15

full scale deflection, sensitivty, internal resistance, resolution
1) moving coil ammeter 300mm 50mm micro A-1 15ohms +/- 0.5mm

2) cathode ray oscilloscope 10cm 0.01 to 10 V cm-1 25M ohms +/- 0.1cm

3) digital voltmeter 20V 0.01 V Steps 2 M ohms +/- 0.01V

(b) i. what instrument is best and use the data to explain why (3)

ii. for the instument you have chosen, calculate the output it would measure for a 200mV signal from the crystal.

2. Relevant equations

none that i can see

3. The attempt at a solution

part i. i said moving coil ammeter beacuse it is most sensitve and has least internal resistance. part ii. had me all ends up. please help!