Which device converts a visible light signal into an instrument analog signal?

The device that converts a visible light signal into an analog signal that can be interpreted by instruments is the photoelectric transducer. This type of transducer operates by detecting light and converting its intensity into an electrical signal. When light impinges on the photoelectric sensor, it generates a proportional analog signal based on the amount of light received. This process allows for the measurement of light levels and enables various applications where light needs to be monitored or controlled in an automated environment.

Other devices listed do not perform the same conversion function. Current-to-pneumatic transducers, for instance, convert electrical signals into pneumatic signals but not light signals into analog signals. Controllers manage system operations but do not convert signals themselves. Photoelectric transducers, on the other hand, are specifically designed for the task of light to analog signal conversion, making them integral in systems that depend on light detection.