17
Measurement Modes
‘Spot’ IR test
The spot insulation resistance test (IR) is selected on the test
mode rotary switch. Select the IR setting and then the required
test voltage using the preconfigured voltage ranges on the
central rotary switch or the V
L
user settable/lockable voltage
range. All preconfigured voltage ranges, but not V
L
, are
adjustable using up and down arrow buttons before and during
the test, but the latter should be limited to the first 10 seconds
of IR and IR(t) tests. Press and hold TEST to start the test.
To set the user defined
lock voltage V
L
,
turn
the central rotary switch
to settings and the mode
switch to IR. The preset
voltage 5000 V will flash
and can be changed
using the up/down buttons. When the required maximum
voltage is displayed, press the OK button to save the setting.
This setting will remain until it is reset.
Whenever V
L
is selected the set voltage is shown on the
display. The voltage lock is useful when, for example, testing
insulation of XLPE cables that should not be tested above
5000 V. The lock function will ensure it does not exceed the
V
L
voltage within the stated output voltage accuracy.
On test completion, insulation capacitance (C) and the Time
Constant (TC) associated with it is calculated and displayed.
Time Constant (TC) = R
insulation
x C
insulation
Timed IR test
A timed test IR(t) will
automatically
terminate an insulation
test after a preset time.
Default timer is set to 1
minute and is
adjustable within the
settings function. This
is a useful feature which saves the user watching the display
for the full duration of the test and the possibility of missing the
1 minute reading.
Turn the central rotary switch to the settings position. Select
IR(t) on the test mode rotary switch. The default time of 1:00
minute will flash prompting the user to select a new time using
the up/down arrow buttons. Press OK to set test duration and
turn central rotary switch to desired test voltage. Press and
hold TEST to start the test.
DAR and PI Insulation Tests
DAR and PI tests are
measurements of
resistance over time
expressed as a ratio of
resistance at time t2
divided by resistance
at time t1. The
assumption is that
insulation temperature does not vary widely over the duration
of the test so the resulting DAR and/or PI value are
temperature independent. Testing should be done at or below
40 ºC, 104 ºF for this assumption to hold.
DAR and PI timers t1 and t2 are set when DAR or PI is
selected on the test mode rotary switch with the central rotary
switch in the settings position. Timer t1 is set first followed by
OFF
500V
1kV
2.5kV
5kV
10kV
V
V
TΩ
USB
PI
DD
SV
DAR
IR(t)
IR
