MI 3205 TeraOhm XA 5kV
Measurements
36
5.4 Averaging options
Filters and additional averaging are built in to reduce the influence of noise on
measurement results. This option enables more stable results especially when dealing
with high Insulation Resistances.
In Insulation Measurement the status of the averaging option is shown in measurement
control window of the LCD screen. The table below contains a definition of the individual
filter options:
Averaging
options
Settling
time
Meaning
- - -
0 s
Averaging is disabled
5 results
5 s
Moving average of 5 results
10 results
10 s
Moving average of 10 results
30 results
30 s
Moving average of 30 results
60 results
60 s
Moving average of 60 results
5.4.1 The purpose of averaging
In simple terms the averaging smooth’s the measured.
There are various sources of disturbance:
AC currents at the mains frequency and its harmonics, switching transients etc,
cause the results to become unstable. These currents are mostly cross talk
through insulation capacitances close to live systems,
Other currents induced or coupled in the electromagnetic environment of the
insulation under test.
Ripple current from internal high voltage source.
dt
t
dU
C
t
i
)
(
)
(
Charging effects of high capacitive loads and / or long cables.
Voltage changes are relatively narrow on high resistance insulation, so the most
important point is to filter the measured current.
Notes:
Any of the selected averaging options increases the settling time.
It is necessary to pay close attention to the selection of time intervals when using
the averaging.
The recommended minimum measuring times when using averaging are the
settling times of the selected averaging option.
