Temperature transducers — RTD output variable: An RTD (resistance temperature detector) produces a change in which electrical quantity for a given change in temperature? The claim says it “produces a voltage.” Decide whether the claim is valid.

Introduction / Context:
Many temperature sensors convert thermal changes to electrical signals, but they do so via different primary variables. Thermocouples generate a voltage (Seebeck effect), whereas RTDs change resistance. Confusing these leads to wrong interface circuits and large measurement errors.

Given Data / Assumptions:

• RTD element (e.g., Pt100/Pt1000) has resistance that varies predictably with temperature.
• Measurement is typically made using a constant current source and measuring the resulting voltage drop, or via a Wheatstone bridge.
• No built-in thermoelectric junctions as in thermocouples.

Concept / Approach:
The primary transduction in an RTD is resistive: R(T) increases with temperature (for platinum). Any observed voltage is a secondary effect produced by test current flowing through that resistance. Therefore, saying an RTD “produces a voltage” misstates the device principle; it “exhibits a resistance change,” and the instrumentation creates and measures voltage proportional to that resistance under known current.

Step-by-Step Solution:

Verification / Alternative check:
RTD datasheets present R–T tables/curves, not Seebeck coefficients. Measurement ICs for RTDs provide precision current sources and ratiometric ADC inputs, affirming resistance-based operation.

Why Other Options Are Wrong:

• Correct: Confuses RTDs with thermocouples.
• “Valid only with constant-current excitation”: Even then, voltage is a measurement product, not the primary transduction.
• “Valid only for platinum RTDs”: All RTDs are resistive by definition.
• “Undetermined…”: Wiring affects error compensation, not operating principle.

Common Pitfalls:
Mixing up thermocouple vs. RTD; overlooking lead-wire compensation (2-, 3-, 4-wire) which addresses resistance measurement accuracy.

Final Answer:
Incorrect.