In instrumentation and control, what does a thermistor primarily measure, considering its electrical behaviour and typical use in sensing circuits?

Introduction / Context:
A thermistor is a temperature-sensitive resistor whose resistance changes predictably with temperature. Thermistors are widely used in HVAC, consumer electronics, battery packs, and industrial controls for accurate temperature measurement and compensation.

Given Data / Assumptions:

• We are distinguishing what a thermistor measures versus what a full circuit outputs.
• Thermistors are not pressure sensors.
• Thermistors require biasing and signal conditioning to produce a voltage or digital reading.

Concept / Approach:
The core quantity a thermistor senses is temperature. In circuits, a thermistor forms part of a divider or bridge so that changes in resistance translate to measurable voltages, but the device itself is a resistor, not a self-powered voltage source. Therefore, the correct identification is temperature measurement.

Step-by-Step Solution:

Verification / Alternative check:
Datasheets specify resistance vs. temperature tables or Steinhart–Hart coefficients, reaffirming temperature as the sensed quantity.

Why Other Options Are Wrong:

Common Pitfalls:
Assuming “sensor” implies a stand-alone voltage source; many sensors are passive and need excitation and conditioning.

Final Answer:
Temperature.