RMS measurements

This section describes RMS measurements

Root mean square (RMS) measurements are supported for all devices. These types of measurements use the so called DSP solver part of the processor. Same solver is used for power sources and thermal models. Number of RMS measurements is not strictly limited.

Table 1. RMS measurement components in HIL toolbox
component component dialog window component parameters

Current RMS measurement

  • Operation mode (PLL based/Fixed frequency)
  • Fundamental frequency

Voltage RMS measurement

  • Operation mode (PLL based/Fixed frequency)
  • Fundamental frequency

Tab: General

There are two operation modes of RMS measurements: PLL based and Fixed frequency.
  • PLL based mode is more general, and it adapts in real time to the signal's frequency. This mode should be used in case of variable frequency signals. In case the measured signal is significantly distorted built-in PLL may fail to lock resulting in inconsistent readings.
  • In Fundamental frequency mode RMS value is measured with predefined fundamental frequency, defined by value set in Fundamental frequency parameter.
Figure 1. General tab in RMS voltage/current measurement’s properties window

Tab: Signal Processing

If Pin to System CPU is checked, signal processing code in the component will be mapped to the System CPU. In this case, execution rates for signal processing code inside the component are defined in the Signal processing settings. If Pin to System CPU is unchecked, signal processing code in the component will be mapped to the CPU according to standard CPU partitioning algorithms. More about this algorithm can be found in the Signal processing settings. In this case, it is possible to specify Slow and Fast execution rates.

If the Signal output property is set to True, the measured RMS value is available on a dynamically added output signal port. If Pin to System CPU is checked, the Output execution rate property defines the output execution rate. If Pin to System CPU is unchecked, the output execution rate is the same as Slow execution rate.

Figure 2. Signal Processing tab in RMS voltage/current measurement’s properties window

Tab: Advanced

In Advanced tab, shown in Figure 3, there is a property called Exact measurement. If its value is set to True, the measurement is calculated as a state variable. In some corner cases, where there are very fast time constants (<1e-5s), setting the Exact measurementflag to true will give more accurate results

Drawbacks of using the exact measurements are:
  1. Might increase the memory usage,
  2. Might require more processing power which may result in larger required simulation step.
Figure 3. Advanced tab in RMS voltage/current measurement’s properties window