Question 544General Subjects - Assistant Engineer70% to pass
For a pneumatic transmission system for instrumentation purposes, if a pneumatic temperature indicator has a calibrated scale of -40 to +40oF, what would be the actual measured temperature 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) 0°F.
In a pneumatic transmission system for instrumentation, the transmitted pneumatic signal pressure is typically in the range of 3 to 15 psig, with 3 psig corresponding to the lower end of the calibrated scale and 15 psig corresponding to the upper end. Since the given calibrated scale is -40 to +40°F, and the transmitted pressure is 9 psig, the actual measured temperature would be the midpoint of the scale, which is 0°F.
The other options are incorrect because:
A) -10°F would correspond to a lower pneumatic signal pressure, around 4.5 psig.
C) +10°F would correspond to a higher pneumatic signal pressure, around 11 psig.
D) +25°F would correspond to an even higher pneumatic signal pressure, around 13.5 psig.
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