Which term best describes the overall function of a transmitter in instrumentation?

The overall function of a transmitter in instrumentation is best described as "Indication and Transmission." This reflects the primary role of a transmitter, which is to measure a specific process variable—such as temperature, pressure, or flow—and then indicate this value for monitoring purposes, as well as to transmit this information to a control system or display.

Transmitters convert the physical measurement to an electrical signal that can be easily processed, displayed, or recorded, allowing for real-time monitoring and control of industrial processes. By sending the measured data to a system, they ensure that operators have the necessary information at their fingertips to make informed decisions about the process.

While other terms like "Process Variable Measurement" might relate to specific aspects of the function of a transmitter, they do not encompass the full range of activities that a transmitter performs, including both indicating the process variable and transmitting the data to other systems. Therefore, "Indication and Transmission" captures the holistic role of transmitters in instrumentation.