What device receives a signal representing a variable and converts it into an electrical or digital signal?

A transducer is designed to receive a signal that represents a physical variable, such as temperature, pressure, or flow, and converts that signal into an electrical or digital format. This conversion is essential for various applications, especially in automation and control systems, where monitoring and response require precise and accurate readings of the physical variable.

Transducers can be utilized for a wide range of measurements and are integral in systems where data must be collected for analysis or feedback to controllers. For example, in a boiler system, temperature transducers can convert temperature readings into electrical signals that can be interpreted by control systems to maintain optimal performance.

The other options, while related to signal processing and control, do not fulfill the same role as a transducer. A transponder is typically used in communication systems, a controller manages processes based on inputs (which could come from a transducer), and an indicator merely displays information but does not perform any conversion of signals. Understanding the specific function of a transducer helps clarify its importance in monitoring and controlling systems effectively.