ZES ZIMMER LMG450, Руководство пользователя

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100 Harmonics measuring mode (option L45-O8) LMG450
120
8.2 Measuring ranges (Range)
The settings are the same like in 5.2 ‘Measuring ranges (Range)’, but in this mode you have no
autorange function.
8.3 Definition of measuring values
The following basic definitions are used:
n
The harmonic order.
T The time of an integer number of the periods of the synchronisation signal. The integer
factor depends on the frequency of the basic wave:
Basic wave range / Hz Number of measured
periods
Sample frequency
divider
Automatically
selected filter
640-1280 16 1 HF-Rejection
320-640 8 1 HF-Rejection
160-320 4 1 HF-Rejection
80-160 2 1 18kHz
40-80 2 2 6kHz
20-40 2 4 2.8kHz
10-20 2 8 1.4kHz
5-10 2 16 700Hz
2.5-5 2 32 350Hz
1.25-2.5 2 64 175Hz
0.625-1.25 2 128 87.5Hz
The ‘sample frequency divider’ defines, how the sampling frequency of about 50kHz is divided
for this measuring.
Voltage and current
true root mean square:
Utrms
T
u t dt
t
T
=
=
∫
1
2
0
( ) Itrms
T
i t dt
t
T
=
=
∫
1
2
0
( )
total harmonic distortion:
∑
=




= 99
2
2
1
n
n
U
U
Uthd
∑
=




= 99
2
2
1
n
n
I
I
Ithd
Only with FDIV set to 1 you get the THD values of the signals.
The harmonic components are calculated to meet the following:
u t U
n
n t
n un
( ) sin( )
=
=
+
∑
2
0
99 ω ϕ
i t I
n
n t
n in
( ) sin( )
=
=
+
∑
2
0
99 ω ϕ