Are functional effects of any cause that result in behaviour of the control that is not suitable for the task. A differentiation is made between:
Active errors:
Errors that trigger control functions without the conditions defined in the program.
Passive errors:
Errors that block control tasks despite the fact conditions are met as per the program.
Self manifesting errors:
Errors that make themselves apparent independent of the operation or function of the control at the moment of occurrence.
The self manifestation of errors is generally only achievable by means of redundancy and/or special circuitry and/or monitoring functions (diagnostics).
Not self manifesting errors:
Errors that do not necessarily make themselves apparent by means of an effect at the moment of occurrence.
Not dangerous errors:
Errors that do not cause a hazard for man and/or machine.
Dangerous errors:
Errors that cause a hazard for man and/or machine.
The definition of a dangerous error in a control can only be derived from the interaction of the control with the device to be controlled. Here both active errors (e.g. unintended placing in operation) and also passive errors (e.g. prevention of intended standstill) can be dangerous errors (DIN 19 237).
Sleeping errors:
Errors that only occur if another error has occurred. Example: A seal between two circuits has failed. As long as both circuits work, the failure is not noticed, however if one circuit fails the other fails with it.