CRS Sensors, I/O & Vision Systems 1 — Questions and Answers
Question 1: Which type of sensor is most commonly used to measure the rotary position of a robot joint?
- Incremental or absolute encoder (Correct answer)
- Capacitive proximity sensor
- Ultrasonic rangefinder
- Inductive load cell
Correct answer: Incremental or absolute encoder
Encoders (incremental or absolute) convert shaft rotation into digital position feedback, providing the precise joint angle data required for robot motion control.
Question 2: What is the primary purpose of a force/torque sensor mounted at a robot's wrist?
- To detect and respond to contact forces during task execution (Correct answer)
- To measure electrical current draw of the end-effector
- To calibrate the robot's zero-point reference
- To sense ambient temperature near the tool
Correct answer: To detect and respond to contact forces during task execution
A wrist-mounted force/torque sensor measures the forces and moments applied at the tool, enabling compliant motion, assembly tasks, and collision detection.
Question 3: An inductive proximity sensor will reliably detect which type of target?
- Ferrous or non-ferrous metallic objects (Correct answer)
- Transparent plastic films
- Wooden pallets
- Cardboard packaging
Correct answer: Ferrous or non-ferrous metallic objects
Inductive proximity sensors generate an electromagnetic field and detect eddy currents induced in electrically conductive (metallic) targets only.
Question 4: In a robotic I/O system, what is the function of a sourcing (PNP) digital output?
- It supplies voltage to the load when active (Correct answer)
- It sinks current from the load when active
- It converts analog signals to discrete levels
- It provides galvanic isolation between the robot and field device
Correct answer: It supplies voltage to the load when active
A sourcing (PNP) output provides the positive supply voltage to the connected load, completing the circuit through the load to the common ground.
Question 5: What does an absolute encoder provide that an incremental encoder does not?
- A unique position value at every shaft angle without requiring a homing cycle (Correct answer)
- Higher resolution counts per revolution
- Faster signal update rates
- Immunity to electrical noise
Correct answer: A unique position value at every shaft angle without requiring a homing cycle
An absolute encoder outputs a unique digital code for every angular position, so the robot always knows its exact joint angle even after a power loss, eliminating homing.
Question 6: Which sensor technology is best suited for detecting a transparent glass bottle on a conveyor in a robotic cell?
- Capacitive proximity sensor (Correct answer)
- Inductive proximity sensor
- Magnetic reed switch
- Hall-effect sensor
Correct answer: Capacitive proximity sensor
Capacitive sensors detect changes in dielectric constant and can sense non-metallic materials including glass, liquids, and plastics that inductive sensors cannot detect.
Question 7: What is the purpose of the analog-to-digital converter (ADC) in a robotic controller's I/O module?
- To convert continuous voltage or current sensor signals into digital values the controller can process (Correct answer)
- To amplify low-level sensor signals before transmission
- To provide galvanic isolation on digital input channels
- To convert robot program instructions into motor drive commands
Correct answer: To convert continuous voltage or current sensor signals into digital values the controller can process
An ADC samples a continuous analog signal (e.g., 0–10 V from a pressure sensor) and represents it as a discrete digital number that the controller's CPU can read and act on.
CRS Sensors, I/O & Vision Systems 1
Which type of sensor is most commonly used to measure the rotary position of a robot joint?