Which of the following is an element in direct contact with the process variable to be measured that senses a change and provides a signal to the transmitter?
A) Sensor
B) Indicator
C) Recorder
D) Controller
Answer: A
Explanation: A) Correct. A sensor is an element in direct contact with the process variable to be measured that senses a change and provides a signal to the transmitter.
B) Incorrect. An indicator shows the current condition of a process variable, usually through a visual representation such as a needle on a scale in a gauge or a digital readout.
C) Incorrect. A recorder is an instrument used to document variables such as pressure, speed, flow, temperature, level, and electrical units.
D) Incorrect. The controller receives information from the transmitter in the form of a pneumatic or electronic signal, compares that input signal to the reference set point, and sends a corrective output signal to the final control element, typically a control valve.
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