Which measurement device is typically used for detecting temperature changes?

The thermometer is the device typically used for detecting temperature changes, which makes it the most suitable choice for this question. A thermometer operates based on materials that expand or change in state in response to temperature variations, allowing it to provide a direct reading of the temperature.

Thermocouples, while also effective for measuring temperature, function by using the voltage generated at the junction of two different metals, making them more suitable for applications requiring high accuracy or in extreme conditions. Though they are commonly used in industrial settings to monitor temperature, they operate on a principle that is less intuitive than the traditional way a thermometer measures temperature.

Pressure gauges are utilized for measuring the pressure of gases or liquids, and they do so using principles that are unrelated to temperature measurement. Similarly, flow meters are designed to measure the flow rate of fluids, which does not pertain to temperature changes.

Thus, choosing the thermometer is appropriate as it directly correlates with the purpose of detecting temperature changes, aligning perfectly with the question's focus.