Detailed Description

The Derivative operator calculates the mathematical derivative (ie. rate of change per second) of the input value.

Arguments and Properties

The Derivative operator calculates the derivative based on the previous processing cycle input values. Therefore, when the value is not updated during CalculationCycles time, then the derivative calculates to 0 on that processing cycle. So you must take care that the operator source value update frequency is at least the same (or even better 2 or more times higher) than the frequency of the DerivativeOperator. Alternatively you can compensate the processing frequency difference by increasing the CalculationCycles property to match formula.

`\text{CalculationCycles}=\text{frequency of the derivative operator}/\text{frequency of the source value}`

You can also use CalculationCycles higher than 1 while calculating derivatives of different sensors to reduce the false derivatives caused by sensors noise.

When operator is used inside a signal its default input is automatically tied to signal's InternalValue or previous operator's output. Its default output is automatically tied to next operator's input or to signal's Value. See also CDP Operator Usage In CDP Signals.

Example

Below is an example plot with a Sine signal (cyan) and the same signal with a Derivative operator applied (orange) plus the same signal with second Derivative operator applied (yellow):

Actual Processing Code of the DerivativeOperator

unsigned int DerivativeOperator<T>::Process()
{
  auto calculationCycles = static_cast<unsigned char>(m_calculationCycles);
  if (calculationCycles == 0)
  {
    m_calculationCycles = 1;
    calculationCycles = 1;
  }
  auto prevAverage = GetCalculationCyclesAverage();

  m_prevValueHistory.push_back(static_cast<T>(m_input));
  while (m_prevValueHistory.size() > calculationCycles)
    m_prevValueHistory.pop_front();

  m_output = (GetCalculationCyclesAverage() - prevAverage) / CDPOperator<T>::GetOperatorPeriod();

  return STATUS_OK;
}