I Don’t Want No D*** Diagnostics!Friday, May 04, 2012
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After a false trip incident, I heard a control engineer express his displeasure with the automatic diagnostics in a new safety rated transmitter. The transmitter diagnostics were annunciated by sending the analog current out of range. In this case, the current went to 3.6 milliamps. The problem was that the logic solver was configured for a low trip and did not recognize out of range signals as a diagnostic alarm. It interpreted the signal as a trip condition. The safety instrumented function (SIF) worked perfectly. It did the job for which it was programmed.
I can see how the diagnostics are blamed for the problem, but how could anyone not want a product that can tell them when it fails? …