User manual

GMC-I Messtechnik GmbH 21
9 Measuring Low-Value Resistance of up to
10 Ohm (protective conductor and equipotential
bonding conductor)
According to the regulations, the measurement of low-value resis-
tance at protective conductors, earth conductors or bonding con-
ductors must be performed with (automatic) polarity reversal of
the test voltage, or with current flow in one direction (+ pole to PE)
and then the other (– pole an PE).
Attention!
!
In the measuring function R
LO
, measurements are per-
formed with currents about 200 mA.
Please check before measuring whether your DUT or
your circuit is designed for these high current values.
Attention!
!
Low-value resistance can only be measured at voltage-
free objects.
Select Measuring Function
➭ Select the Rlo measuring function with the rotary switch.
Connection
➭ Connect the device under test to the + and COM jacks.
Set Polarity Parameter (direction of current flow)
➭ Select a polarity option or automatic polarity reversal.
Measuring ROFFSET
When using extension cables with resistance of up to 5.00 Ω,
their resistance can be deducted automatically from the measure-
ment results. Proceed as follows:
➭ Short-circuit the end of the measurement extension cable with
the second test probe at the instrument.
➭ Start measurement of offset resistance with OFFSET.
Note
If the difference between RLO+ and RLO– is great than
10% with automatic polarity reversal, no offset is
accepted. A pop-up window appears which must be
acknowledged by any desired key. The respectively
smaller value is otherwise stored to memory as an offset
value.
The maximum offset value is 5.00 Ω. Negative resis-
tances may result due to the offset value.
The permissible value for R
OFFSET is between 0.00 and 5.00 Ω.
In the case of values of greater than 5.00 Ω, a pop-up window
appears and the value is not accepted. The error message must
be acknowledged and/or cleared by any desired key.
The measured R
OFFSET value will now be deducted from the actual
measurement value for all subsequent R
LO
measurements.
R
OFFSET can be deleted at any time by pressing the OFFSET CLEAR
key.
Note
Only use this function when performing measurements
with extension cables.
When different extension cables are used, the above
described procedure must always be repeated.
R
LO
HELP
+
COM
R
LO
+
COMSHIELD
R < 10 Ω
R
LO
R
x
0V !
!
Polarity: ± to PE