Comparing resistive, capacitive and infra-red touch screens

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Quick Questions

Shade in the A or B circle for each question.

1. Which touch screen type detects touch when two conductive layers are pressed together?

A Capacitive

B Resistive

2. Which touch screen type senses the electric charge of a finger?

A Capacitive

B Infra-red

3. Which touch screen type detects touch when a grid of light beams is broken?

A Resistive

B Infra-red

4. A user wearing thick gloves wants to use a touch screen on a factory machine. Which type works best?

A Resistive, because pressure from any object works

B Capacitive, because gloves carry electric charge

5. Which statement about multi-touch (pinch to zoom) is most accurate for a modern smartphone?

A Capacitive screens handle multi-touch very well

B Resistive screens handle multi-touch best

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Resistive: top layer pressed onto bottom layer		AResistive screens detect touch by pressure on layers, and their extra layers make the picture less clear than capacitive screens.
2Capacitive: finger changes electric charge		BCapacitive screens need the electric charge of a bare finger, so gloves do not work. Resistive screens work with gloves because they sense pressure.
3A screen that detects a broken beam of light is best for a large public display		CTouch is detected by pressure pushing two layers together, so a gloved finger or stylus works
4A phone needs a clear, multi-touch screen that is sensitive to a bare finger		DInfra-red: beams across the screen
5Capacitive screens work with any object, like a glove		ETouch is detected from the charge of a bare finger, so gloves and plastic styluses do not work and multi-touch is easy
6Resistive screens are the clearest and detect touch using electric charge		FCapacitive: smartphone screen

Definitions

resistive, capacitive, infra-red

Fill in the Blanks

Complete each line of code by filling in the missing parts.

OUTPUT _________ + " senses pressure"

IF object = ______ THEN works ← TRUE

IF beam = "broken" ____ touch ← "infra-red" ENDIF

IF screen = "resistive" THEN ______ "pressure" ENDIF

device ← "phone" screen ← "__________"

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A screen = "resistive"

B detects = "pressure"

C touch_with = "bare finger only"

D multi_touch = False

Question 2

A screen = "capacitive"

B detects = "pressure on layers"

C multi_touch = True

Question 3

A screen = "infra-red"

B detects = "electric charge"

C cost = "high"

Question 4

A needs_stylus = True

B if needs_stylus:

C choice = "capacitive"

D print(choice)

Question 5

A device = "phone"

B if device == "phone":

C screen = "capacitive"

D multi_touch = False

E print(screen)

Answer Key

Comparing resistive, capacitive and infra-red touch screens

Section A: Quick Questions

B — Resistive

A — Capacitive

B — Infra-red

A — Resistive, because pressure from any object works

A — Capacitive screens handle multi-touch very well

Section B: Match the Pairs

Resistive: top layer pressed onto bottom layer → Touch is detected by pressure pushing two layers together, so a gloved finger or stylus works

Capacitive: finger changes electric charge → Touch is detected from the charge of a bare finger, so gloves and plastic styluses do not work and multi-touch is easy

A screen that detects a broken beam of light is best for a large public display → Infra-red: beams across the screen

A phone needs a clear, multi-touch screen that is sensitive to a bare finger → Capacitive: smartphone screen

Capacitive screens work with any object, like a glove → Capacitive screens need the electric charge of a bare finger, so gloves do not work. Resistive screens work with gloves because they sense pressure.

Resistive screens are the clearest and detect touch using electric charge → Resistive screens detect touch by pressure on layers, and their extra layers make the picture less clear than capacitive screens.

Section C: Definitions

resistive, capacitive, infra-red — Resistive senses pressure on layers; capacitive senses a finger's electric charge; infra-red senses a broken light beam. How touch is detected decides which device each suits.

Section D: Fill in the Blanks

OUTPUT resistive + " senses pressure"

IF object = finger THEN works ← TRUE

IF beam = "broken" THEN
  touch ← "infra-red"
ENDIF

IF screen = "resistive" THEN
  OUTPUT "pressure"
ENDIF

device ← "phone"
screen ← "capacitive"

Section E: Spot the Error

C — A resistive screen works by pressing layers together, so a stylus, a gloved finger or a bare finger all work. Only a capacitive screen needs a bare finger.

B — A capacitive screen detects the electric charge of a finger. Sensing pressure on layers is how a resistive screen works.

B — An infra-red screen detects a touch when an object breaks a grid of infra-red light beams. Sensing electric charge is capacitive.

C — A stylus does not carry the electric charge a capacitive screen needs. A resistive screen works with a stylus because it senses pressure.

D — Capacitive screens support multi-touch, such as pinch to zoom on a phone. The line should be multi_touch = True.