Information system failures (due to sensors, instruments, and components) should result in distinct display changes, which directly indicate that depicted plant conditions are invalid.
Additional Information:
The information system should be designed so that failures in instrumentation are readily recognized by operators. When panel instruments, such as meters, fail or become inoperative, the failure should be apparent to the user (e.g., through off-scale indication). This may be more difficult to determine in complex graphics, and thus, should be carefully evaluated.