Reference Manual
Power Analyzer EMM5
Rev. 11
2018-07
5
2
Measurement system
The EMM5 is designed to acquire all necessary data to provide full information in a 3-phase power distribution system.
This requires the measurement of the three voltages L1/2/3 versus the N connector and the three currents in L1/L2/L3.
Additionally, the current in N can be measured or, if desired, it can also be calculated from the data for I1/I2/I3 (but this
will be less accurate due to calculation and rounding errors).
The EMM5 provides separate input terminals for device supply and measurement, so the measurement inputs are
completely independent. Of course, measurement and supply may be connected to the same power grid.
For the most measurement values, minimum and maximum is stored and they are available for the user if necessary.
2.1
Data collection
The waveforms of the signals (=voltage or current) on the 6 (7 with N-current) input channels are sampled by the data
collection logic of the EMM5. This supplies the software with enough information to calculate all the values.
The sampling of the input signal needs to be synchronized to the input signal, so the EMM5 needs at least one input
signal for the voltage L1-N to be able to do calculations. If this voltage is too small or even disconnected, the device
will not be able to do any measurements. This mechanism is also used to provide the frequency reading.
The data collection circuitry for the voltage channels uses the four terminals L1, L2, L3 and N which have
to be connected in accordance to the connection diagram. As a minimum, the L1/L2/L3 terminals have to
be connected while N can be left floating. In this case, N is artificially generated inside the device by three
resistors. Connection of the N-terminal overrides this high-impedance resistor circuit. The voltages can be
connected directly (with respect to the maximum rating) or via transformers. The voltage transformer factor can be set
in the EMM5.
The three (four with N) current inputs use two terminals each, labelled “K” and “L”. The neutral current can be
measured, but if necessary it can also be calculated with the other 3 currents. Current transformers have to be used for
the measurement. The current transformer factors can be set in the EMM5. Each channel is additionally equipped with
an input filter. This protects the system from being damaged by transients with high frequencies like voltage spikes and
is mainly used to ensure proper sampling, synchronisation and measurement in presence of high frequency harmonics.
Always make sure, you don’t exceed the maximum ratings of voltage and current channels. The ratings
and a connection diagram are available on the labels on the back side of the device.
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