Which of the following is not considered a discrete input?

A temperature sensor is not considered a discrete input because it typically provides a continuous range of values rather than distinct, separate states. In industrial automation and control systems, discrete inputs are typically binary in nature, indicating whether a condition is true or false, on or off, such as those from limit switches. These inputs represent specific conditions like whether a machine part has reached a certain position or limit, making them fundamentally different from sensors that measure variables like pressure, temperature, or flow, which can vary gradually across a spectrum of values.

In contrast, pressure sensors, flow meters, and limit switches all serve different roles, but only limit switches provide a simple binary signal. Pressure sensors and flow meters provide continuous data—how much pressure or flow exists—whereas temperature sensors also continuously measure thermal values. Hence, the continuous nature of a temperature sensor’s output distinguishes it from discrete inputs, making it the correct choice in this context.