Temperature sensors – thermistors in resistance thermometry A thermistor used as the sensing element in a resistance thermometer has a high temperature coefficient of resistivity. A thermistor is best described as a:

Introduction / Context:
Thermistors are widely used temperature sensors whose resistance changes strongly with temperature. Understanding their material class clarifies why they exhibit large, nonlinear temperature coefficients compared to metal RTDs or thermocouples.

Given Data / Assumptions:

• Thermistor acts as the primary sensing element, not merely as wiring or housing.
• High temperature coefficient (often negative, NTC) is typical.
• Device is a bulk solid component.

Concept / Approach:
Thermistors are ceramic or polymer-based semiconductor materials (commonly metal-oxide ceramics such as Mn, Co, Ni oxides). Their charge carrier concentrations vary strongly with temperature, producing large resistance changes. They are solid-state devices, not liquids, and are not metallic conductors or classic insulators.

Step-by-Step Solution:

Verification / Alternative check:
Manufacturer datasheets describe NTC/PTC thermistors as sintered semiconductor ceramics with specified beta constants, confirming the classification.

Why Other Options Are Wrong:

• Insulator: Resistivity far too high and not the intended behavior.
• Conductor: Metals show small positive temperature coefficients, not large thermistor-like changes.
• Liquid semiconductor: Not applicable; devices are solid components.

Common Pitfalls:
Assuming all resistance thermometers are metallic RTDs. Thermistors differ by being semiconductor elements with much larger sensitivity but reduced linearity and narrower temperature range.

Final Answer:
solid semiconductor