Behavior of Calculated Signals Depending on the Status Flag

In an MDF measure file, for sample additionally two flags are available: One for indication whether a value is available at a certain time stamp, and another which indicates whether a recorded value is valid or not.

Each of the flags can be True or False, therefore the following four combinations are possible:

Has a value	Value is valid	Description	Example
TRUE	TRUE	Regular sample
FALSE	TRUE	No sample at this point	Time stamps before the first sample of the signal is available
TRUE	FALSE	Error sample with value
FALSE	FALSE	Error sample with no value	Integer division by 0

For calculated signals the states of the flags of input signals are considered for the calculation result.

This can be summarized as follows:

• No value cases

  • The meaning is the same as if the sample (including time stamp) were missing completely.
  • The advantage is that with this flag a No value of one signal can be combined with other signals in the same group which still have a sample at the same point.
  • The result of a calculation on No value will also be marked as No value (unless the interpolation with other signals causes there to be a sample).
  • The state of stateful operations (like integral) will not update.

• Error cases (both with and without value)

  • If any input sample has an error (i.e. is invalid), the error is propagated to the calculation result.
  • The only exception is if the input sample does not matter, e.g. true? 3: error results in 3.
  • Errors are also propagated into the state of stateful operations.
  • Thus accumulating operations (like e.g. Integral) will stay on error as long as the error sample is part of the accumulation range.