What is a simple type of sensor used to detect contact with an object?

• A. Photocell
• B. Switch
• C. Microphone
• D. Altimeter

Answer: (B)

Detecting contact with an object is typically done with a switch, a simple contact sensor. When something presses the switch, the internal contacts either close or open, producing a clear on/off signal for a controller. This straightforward mechanism makes switches ideal for confirming that physical touch has occurred, such as a button press or a limit sensor at the end of travel. You’ll often see normally open or normally closed variants, chosen based on how you want the signal to behave when there’s no contact. The other devices sense non-contact phenomena: a photocell detects light levels to infer presence, a microphone detects sound, and an altimeter measures altitude. Because they don’t rely on touching the object, they don’t provide direct confirmation of contact, making the switch the simplest and most reliable choice for detecting physical contact.