ZES ZIMMER LMG450, Руководство пользователя

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Z E S ZIMMER Electronic Systems GmbH Chapter 5
77
5 Normal measuring mode
In the normal measuring mode the LMG450 works as a four channel power meter. The
voltage, current and power are measured directly, many other values are derived from these
values.
5.1 Measuring configuration (Measuring)
When you have come to this menu by pressing Measure you first have to choose Norm(a)l to
enter this mode. With the rotary knob you can select three tabs (‘Globals’, ‘Group A’ and
‘Group B’). Pressing the rotary knob, you can do several settings in each tab.
5.1.1 Globals tab
Here you setup all values which are global to the instrument (independent from the groups).
Cycle Here the cycle time in seconds is defined. Valid values are from 0.05s to 60s. Any
value in steps of 10ms is allowed. A value of 0ms defines the external cycle time. See
chapter ‘14.1.1, External Synchronisation (Sync.)‘ and following.
During every cycle time the values of voltage, current and power are measured. At
the end of each interval the measured values are computed to the displayed values.
The cycle time has always to be bigger or same like the (fundamental or basic) period
time of the signal.
Aver Here you can setup, how many measuring cycles are averaged for the display. For
example: If you choose 5 cycles, the display will always be averaged over the last 5
cycles (sliding average!).
Wire Here you can setup, with which wiring you want to measure. Please see chapter 2.4,
‘The group concept’ for further details.
Aron This point is only available when you have chosen wiring ‘A:1+2 B:3+4’.
If you connect a 3 phase 3 wire system in aron circuit (see chapter 3.3.5, ‘Measuring
circuit for measuring efficiency of 3/3phase systems’) you have to measure the
voltages U
13
and U
23
. U
12
is calculated by the instrument. But usually you would use
the three voltages U
12
, U
23
and U
31
. So you measure U
13
instead of U
31
with U
13
=-U
31
.
For most values this does not matter, but in the scope display, you would see, that U
13
has not 120° against U
12
but 60°. This is physically correct (you see the voltages
connected to the instrument), but this is not what you expected. So if you switch the
Aron setting to ‘on’ the display of U
13
is inverted, so that you see U
31
.
Only in the case you have a real 2 phase 3 wire system, you should set Aron to ‘off’