Consider the following statements regarding industrial sensors:1.Inductive proximity sensors are used to detect metallic objects without physical contact.2.Capacitive sensors can detect both metallic and non-metallic (liquid, plastic) materials.3.RTDs (Resistance Temperature Detectors) are less accurate than thermocouples for high-precision measurements.Which of the statements given above is/are correct?

Correct Answer: A - 1 and 2 only

Quick Concept Explanation

Inductive proximity sensors detect conductive/metal targets through electromagnetic field changes. Capacitive proximity sensors respond to dielectric changes and can detect metals, plastics, powders and liquids. Key relation: Pt100: ~100 Ω at 0°C (standard platinum RTD).

Exam focus: Accuracy/stability → RTD; very high temperature/rugged → thermocouple. Common trap: RTDs are not generally less accurate than thermocouples for precision measurement.

Statement-wise Verification

• Statement 1 - Correct.
  Inductive proximity sensors are used to detect metallic objects without physical contact.
  Inductive proximity sensors detect conductive/metal targets through electromagnetic field changes.
• Statement 2 - Correct.
  Capacitive sensors can detect both metallic and non-metallic (liquid, plastic) materials.
  Capacitive proximity sensors respond to dielectric changes and can detect metals, plastics, powders and liquids.
• Statement 3 - Incorrect.
  RTDs (Resistance Temperature Detectors) are less accurate than thermocouples for high-precision measurements.
  The correct principle is: RTDs are valued for accuracy and stability over moderate temperature ranges, whereas thermocouples cover much higher ranges and rugged conditions.

Core Concept

Inductive proximity sensors detect conductive/metal targets through electromagnetic field changes. Capacitive proximity sensors respond to dielectric changes and can detect metals, plastics, powders and liquids. RTDs are valued for accuracy and stability over moderate temperature ranges, whereas thermocouples cover much higher ranges and rugged conditions.

Formula / Key Relationship

Pt100: ~100 Ω at 0°C (standard platinum RTD).

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2. Option D is incorrect because it includes incorrect statement(s) 3.

Exam Shortcut / Approach

Accuracy/stability → RTD; very high temperature/rugged → thermocouple.

Common Mistake

RTDs are not generally less accurate than thermocouples for precision measurement.

Quick Revision

Inductive Capacitive Sensors and RTD is linked with Proximity and Temperature Sensors, Sensors and Industrial Automation. Accuracy/stability → RTD; very high temperature/rugged → thermocouple.