LEM EM4TII+ - 6 Measurement; Measuring Principle; Formula: Generation of Measured Values

05November2020/V1.0 Page 31/33
6. Measurement
6.1 Measuring principle
The load profiles are recorded in datasets at parameterized intervals.
The measuring circuit comprises a Sigma Delta ADC for each measuring channel which enables
simultaneous capturing of measured values at a sample rate of 4800 Hz. The Sigma Delta method
effectively suppresses high-frequency interference on the channels.
The microprocessor reads in the sampled values and calculates the active power and active energy
over adjustable intervals (standard value = 5 min). The datasets are backed up in Flash memories.
The supply voltage can be selected between 24 and 110V as per EN 50155. Optionally a communication
unit (modem) can be supplied with voltage of 12 V via the EM4TII+.
6.2 Formula: generation of measured values
Measured values are generated at one second intervals from 4800 sample values:
Effective voltage value
4800
4800
1
2
1
2
1,

==
==
n
n
N
n
n
seff
u
N
u
U
Effective current value
4800
4800
1
2
1,

=
=
n
n
seff
i
I
Active power

=
=
4800
1
4800
1
n
nn
iuP
Reactive power

=
=
4800
1
90
4800
1
n
nn
iuQ
n
u
: Sample value for voltage at time point n
n
u90
: Sample value for voltage at time point n shifted by 90°
n
i
: Sample value for current at time point n
N
: Interval of the measuring period from N sample values (4800Hz sample rate)