Lecture 3 - Displacement

Question 1

What measure angular displacement?

Answer 1

Rotary or Angular potentiometers

Question 2

What is used if the angular displacement results in more than one revolution?

Answer 2

a helical multi-turn potentiometer

Question 3

Describe the operation of a parallel plate capacitor?

Answer 3

one plate connected to a shaft. other plate is fixed then AD is measured by overlap area.

Question 4

What are the two types of optical shaft encoders?

Answer 4

Incremental and absolute

Question 5

Describe the operation of an incremental shaft encoder?

Answer 5

a shaft with a disc attached rotates with light shining through equally spaced windows. producing an pulsating light at the light detectors. the number of pulses is proportional to the angle the shaft has travelled and phase differnce shows direction of rotation.

Question 6

Absolute encoder operation?

Answer 6

This differs by producing a binary output signal. if an encoder has 4 tracks then 16 positions are detected in total (2^4=16)

Question 7

What’s an issue with the absolute encoder?

Answer 7

Exact alignment of the windows

Question 8

Describe an optical sensor?

Answer 8

consists of a light source and a detector. light source is often an LED and the detector a Phototransistor