Manual

Gossen Metrawatt GmbH 73
16 Measurement of Insulation Resistance
Attention!
!
Insulation resistance may only be measured at voltage-
free devices.
16.1 General
Select Measuring Function
Connection
2 pole adapter or test
plug
Note
The test instrument always measures insulation between
the L and PE terminals.
N and PE must be interrupted for systems without RCD.
Note
Checking Measurement Cables Before Measurements
Before performing insulation measurement, the test
probes on the measurement cables should be short-cir-
cuited in order to assure that the instrument displays a
value of less than 1 k. In this way, incorrect connection
can be avoided and interrupted measurement cables can
be detected.
Set Parameters
* Freely adjustable voltage (see section 10.8)
Polarity Selection
* AUTO parameter (see section 10.9)
Breakdown Current for Ramp Function
Note
In order to suppress the influence of parallel capacitances
on the device under test when measurement is started,
shutdown at the respective breakdown current I
lim
does
not occur until a minimum voltage of 5 V is exceeded.
Limit Values for Breakdown Voltage
Limit Values for Constant Test Voltage
❏ Test Voltage
A test voltage which deviates from nominal voltage, and is usually
lower, can be selected for measurements at sensitive compo-
nents, as well as systems with voltage limiting devices.
❏ Voltage Type
The “U
INS
” rising test voltage function (ramp function) is used to
detect weak points in the insulation, as well as to determine
response voltage for voltage limiting components. After pressing
the ON/START ▼ key, test voltage is continuously increased until
the specified nominal voltage U
N
is reached. U is the voltage
which is measured at the test probes during and after testing.
After measurement, this voltage drops to a value of less than 10 V
(see section entitled “Discharging the Device Under Test”).
Insulation measurement with rising test voltage is ended:
• As soon as specified maximum test voltage U
N
is reached and
the measured value is stable
or
• As soon as specified maximum test voltage is reached
(e.g. after sparkover occurs at breakdown voltage).
Specified maximum test voltage U
N
or any triggering or break-
down voltage which occurs is displayed for U
INS
.
The constant test voltage function offers two options:
R
ISO
Voltage type: constant
Test voltage : 15, 50, 100, 250, 325, 500, 1000 V
Voltage type: rising/ramp
Earth leakage resistance:
xxx V*
2-pole measurement (selection relevant for report genera-
tion only): measurements between
Lx-PE / N-PE / L+N-PE / Lx-N / Lx-Ly / AUTO*
where x, y = 1, 2, 3
Limit Value:
I > I
Limit
U
INS
(U
INS
)
STOP
Lower limit value:
U
INS
(U
INS
)
Enterable range:
> 40 V … < 999 V
Upper limit value:
Limit Value:
R
INS
< Limit Value
U
L
 R
L
U
INS
(U
INS
)