NATE Air Distribution Practice Test 2025 - Free Air Distribution Certification Practice Questions and Study Guide

PTC (Positive Temperature Coefficient) and NTC (Negative Temperature Coefficient) thermistors are primarily used as sensors. These devices are temperature-sensitive resistors, meaning their resistance changes with temperature.

In the case of NTC thermistors, as the temperature increases, their resistance decreases, allowing them to serve well for temperature measurement and control. Conversely, PTC thermistors increase in resistance with rising temperature, making them useful for overcurrent protection and temperature detection applications.

Because they provide precise readings of temperature changes, thermistors are integral to various applications in HVAC systems, electronic devices, and automotive technology, aligning them squarely in the realm of sensors, which monitor physical parameters and convert them into measurable electrical signals.

The other options, such as actuators, compressors, and filters, serve different functions. Actuators convert energy and cause motion, compressors pressurize gases, and filters remove particulates from air or fluids, none of which relate to the primary function of thermistors as temperature sensors.