For a pneumatic transmission system for instrumentation purposes, if a pneumatic temperature indicator has a calibrated scale of -40 to +40 F, 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?

Question

Accepted Answer

Option B: 0F. Using the standard 3-15 psig range, 9 psig represents the midpoint (50%) of the signal. For a scale of -40 to +40 F, the total span is 80 degrees. 50% of 80 is 40. Adding 40 to the lower range limit of -40 results in 0 F.