MI 3200 TeraOhm 10 kV
Measurements
18
I
L
I
L
I
L
Ut
Ut
I
A
I
A
I
M
I
M
A
A
+OUT
+OUT
-OUT
-OUT
GUARD
Fig. 8. Connection of GUARD terminal to measured object
where:
Ut ........ Test voltage
I
L
......... Leakage current (resulted by surface dirt and moisture)
I
M
......... Material current (resulted by material conditions)
I
A
......... A-meter current
Result without using GUARD terminal: R
INS
= Ut / I
A
= Ut / (I
M
+ I
L
) …incorrect result.
Result using GUARD terminal:
R
INS
= Ut / I
A
= Ut / I
M
……correct result.
It is recommended to use the GUARD connection when high insulation resistance
(>10G
) are measured.
Note:
The guard terminal is protected by an internal impedance (400 K
).
The instrument has two guard terminals to allow easy connection of shielded
measuring leads.
5.3. Filter options
Filters 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
(Insulation Resistance, Diagnostic Test, Step Voltage). In these functions, the status of
the filter option is shown in the top right corner of the LCD screen. The
Table 2
. below
contains a definition of the individual filter options:
Filter option
Meaning
Fil0
Low pass filter with cut off frequency of 0.5 Hz in signal line.
Fil1
Additional low pass filter with cut off frequency of 0.05 Hz in the signal
line.
Fil2
Fil1 with increased integrating time (4 s).
Fil3
Fil2 with additional cyclic averaging of 5 results.
Table 2
.
Filter options
