Coast Guard Exams
Question 556General Subjects - Assistant Engineer70% to pass

For a pneumatic transmission system for instrumentation purposes, if a pneumatic pressure indicator has a calibrated scale of 0 to 1000 psig, what would be the actual measured pressure if the transmitted pneumatic signal pressure to the indicator is 9 psig, assuming the industry standard of 3 to 15 psig is used for instrument air?

AI Explanation
The correct answer is B) 500 psig. The standard pneumatic signal range for instrumentation is 3 to 15 psig. Since the pressure indicator is calibrated from 0 to 1000 psig, and the transmitted pneumatic signal is 9 psig, this would correspond to 500 psig on the indicator's scale. This is because the 3 to 15 psig signal range is linearly mapped to the 0 to 1000 psig scale of the indicator. The other options are incorrect because they do not accurately reflect the linear scaling of the 3 to 15 psig signal range to the 0 to 1000 psig indicator scale.