For an analog electronic transmission system for instrumentation purposes, if an analog pressure indicator has a calibrated scale of 0 to 30 psig, what would be the actual measured pressure if the transmitted analog signal current to the indicator is 12 mA, assuming the industry standard of 4 to 20 mA is used for instrument current?

Question

Accepted Answer

Option C: 15 psig. The 4-20 mA standard provides a 16 mA span. A 12 mA signal is exactly 50% of this span ( (12-4)/(20-4) = 0.5 ). Applying this 50% value to the 0-30 psig calibrated scale results in an actual measured pressure of 15 psig.