CMD420/421 is a current monitoring device that can monitors AC currents using three measuring inputs for overcurrent or undercurrent. The currents are measured as rms values, while the currently measured values are shown on an intuitive LCD display. The measuring channel that works best for an application can be selected using one of the two available buttons, arrow up or arrow down, while the measured values causing the alarm relay to switch are stored.
Users can consider installation-specific characteristic, such as short-time current changes and making currents that are device-specific, due to the adjustable delay times. When it comes to measurement, three standard current transformers can be connected to the respective CMD420/421 device. The transformation ratio "n" of the current transformers can also be set to a factor of n=2000. Finally, the actual current of the installation can be computed by multiplying the measured current by factor "n".