A live-zero transmitter has an offset
A fictional pressure transmitter is specified to produce four to twenty milliamperes over a zero-to-ten-bar measurement range. A displayed signal is twelve milliamperes. A learner divides twelve by twenty and reports six bar, treating the signal as though it started at zero milliamperes. Another subtracts the stated live-zero offset before finding the fraction of span. This written exercise connects no instrument and changes no control setting. It asks the learner to calculate the specified linear value, distinguish a zero pressure signal from an abnormal zero-current observation and avoid claiming that one unexpected reading identifies a unique wiring or process fault without further authorized evidence.
1. What pressure does the stated model give?
Read the worked answer
(12−4)/(20−4) = 0.5 of the ten-bar span, so the indicated value is 5 bar.
2. What does zero current establish?
Read the worked answer
It is outside the stated ordinary measurement range and warrants appropriate diagnosis. It does not by itself uniquely establish one broken wire, power fault or process condition.