A failure report states that a safety transmitter signaled a high pressure in a vessel and initiated a trip. Other pressure measurements did not indicate any high pressure. A diagnostic in the safety transmitter detected that its voltage reference had drifted out of range and initiated a high alarm current signal of 21 mA. The PLC was not programmed to recognize this current level as a diagnostic indication.

Which of the following is true?

A. The failure should be classified as random and counted in the failure rate analysis. Since the failure was counted, no further action is necessary.

B. The failure is counted in the failure rate analysis, but the report indicates a systematic improvement is required to reduce the false trip rate by reconfiguring the PLC to recognize out-ofrange current signals as a diagnostic indication.

C. The failure is systematic and should not be counted as a random failure. The PLC configuration must be improved.