Block 3 - lecture 8

Question 1

Potentiometric sensor?

Answer 1

A coil of wire with adjustable connectors to change the length of the wire

Question 2

circuit for a potentiometric sensor?

Answer 2

as the feedback resistor in an inverting amplifier circuit

Question 3

equation for potentiometric inverting amplifier output?

Answer 3

Vout = -Rsensor/R * Vin

Question 4

capacitive sensor?

Answer 4

• two places move together/apart (distance reduces capacity)

- two plates move over each other (area reduction reduces capacity)

Question 5

induction sensors?

Answer 5

• permeable core moves through an AC solenoid

- solenoids either side have a current induced, proportional to the distance from the centre

Question 6

types of level sensors?

Answer 6

• concentric cylindrical capacitor

- above/below surface ultrasonic sensor

Question 7

strain sensor?

Answer 7

extension (strain) in wire increases the length and decreases the area, thus increasing the resistance

Question 8

equation for resistance from strain?

Answer 8

resistance change = 2Rstrain

Question 9

types of motion sensor?

Answer 9

• rectilinear (movement in a direction)
• angular
• vibration
• shock (sharp acceleration)

Question 10

accelerometer?

Answer 10

mass on a spring

Question 11

important accelerometer considerations?

Answer 11

• should cover expected accelerations

- should have an natural frequency higher than that being measured