Question 245General Subjects - 1st Asst/Chief

The correct answer is D) 4 mA or 3 PSI. The 'live zero' for a 4-20 mA or 3-15 PSI pneumatic controller refers to the minimum value of the output range, which is 4 mA or 3 PSI respectively. This is the value that represents the zero or bottom end of the measurement or control range for the device. The live zero is not zero, but rather the lower end of the specified output range, which allows for detection of faults or issues with the system. The other options are incorrect because A) refers to the input span, not the output range, C) is incorrect as the live zero is not zero, and B) is partially correct but does not fully capture the definition of live zero.