Overview Measured value plausibility

This block checks measured values for plausibility before they are processed further. It checks the permissible range, the maximum change within a period of time and the absence of an update. An implausible value is not passed on; instead the last valid value is held or a substitute value is put out, depending on the setting. This keeps a failing or jumping sensor from disturbing a downstream control loop.


Inputs

WT Value Measured value to be checked.



Outputs
WT Value Checked value. If the input value is plausible it is put out unchanged, otherwise the configured behaviour applies.
UG Invalid Becomes 1 as long as the input value is detected as implausible.
GR Reason Reason for the objection:
  • 0 = valid
  • 1 = below minimum
  • 2 = above maximum
  • 3 = change too large
  • 4 = no update



Parameters
Minimum Smallest plausible value.
Maximum Largest plausible value.
Maximum change Largest permissible change within the period. 0 = no check. The permissible change is scaled to the interval that has actually elapsed between two values.
Period for change (s) Reference period for the maximum change, in seconds.
Monitoring time (s) If an update is missing for longer than this time, the value is considered invalid (reason 4). 0 = no check. Every telegram to the address of the input counts as an update, even if the value stays the same. If the input is only connected internally to another block, only changes of value are detected.
Behaviour when invalid
  • Hold last valid value: the output keeps the value last detected as valid. As long as no valid value has occurred yet, the substitute value is put out.
  • Output substitute value: the output is set to the substitute value.
  • Pass value through: the input value is put out anyway, only the message is given.
Substitute value Value that is put out for an invalid measured value.

See also: Measured value monitoring, Min/Max filter

See also common parameters of all function blocks.