What device is used to convert environmental input into a signal for a control program?

The correct answer is a sensor because its primary function is to detect environmental input—such as temperature, pressure, light, or motion—and convert that information into signals that can be used by a control program. Sensors play a critical role in automation and control systems, as they provide the necessary data that inform decisions and actions taken by controllers.

Through the conversion of physical phenomena into readable electrical or digital signals, sensors enable systems to react to changes in the environment. This capability is essential for feedback loops in control systems, where the performance of a system must be monitored and adjusted based on real-time data. Without sensors, control programs would lack the vital external information required to function effectively, making them unable to respond appropriately to varying conditions.

In contrast, an actuator is responsible for carrying out commands by moving or controlling mechanisms, while a transmitter typically refers to a device that sends data. A controller processes the input signals received from sensors to execute control actions, but it does not convert environmental input itself. Each component has a distinct role, with the sensor being the key device that initiates the process by providing the necessary environmental data.