Megger Programma Sverker 750, Руководство пользователя, Страница: 12 / 76

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3.6 Ammeter &
voltmeter
Sverker is equipped with an ammeter and voltmeter.
These instruments can also be used to display
resistance, impedance, phase angle, power and
power factor. Moreover, these instruments can be
used to perform measurements in external circuits.
In both cases, the values appear on the display.
The ammeter measures one of the following:
• Current at one of the current outputs
0-100 A, 0-40 A or 0-10 A.
• Current in an external circuit connected to
the Sverker 750/760 ammeter panel input
(marked
).
You select the desired measurement site (test point)
using the button marked A, whereupon a indicator
lamp lights at the selected measurement site.
The voltmeter shows the voltage connected to the
voltmeter input (marked V) on the panel. This input
is always activated.
The ammeter and voltmeter both change ranges
automatically, but they can also be changed manu-
ally. For AC, they measure true RMS value. You
can change from AC to DC and vice versa.
Note! When using AUTO RANGE the measured
value can be totally wrong. This can
happen when a previous value was in
another range than the present value.
Set the correct range (see section 9.5)
and/or repeat the same test again.
A HOLD (freeze) function permits you to measure
voltages and currents having durations as short as a
quarter of the mains cycle. When the timer is
stopped, the current and voltage values are frozen. If
the timer is not stopped, the values present when the
current was interrupted are frozen. The hold func-
tion is engaged by pressing the button marked
HOLD. - - - - can sometimes appear during measure-
ment of high-speed AC cycles when the hold
function is invoked. This means that no value could
be presented because the cycle was too short.
If O.F. (means overflow, i.e. a value beyond the
measurement range) appears, the cycle being
measured may have been so fast that there wasn’t
time for automatic range changing. In such case,
you should repeat the measurement. The range-
changing system is memory-equipped, and repeating
your measurement may give it time to make the
change properly.
When current and/or voltage fluctuate widely, a
filter can be engaged to make reading easier. The
filter performs an averaging function.
Instead of having current and voltage shown in
amperes and volts, you can have them shown as a
percentage of a given current or voltage (the relay
protection equipment’s setting for example). A
flashing current value means that the value is less
than 1% of the range being used. To get a more
accurate current reading, you can then measure via
the ammeter input.