Martindale Electric VT25 Instruction Manual page 6

the parts to be tested, the voltage tester may
discharge temporarily the interference voltage
to a level below the ELV, but it will be back to
the original value when the voltage tester is
removed.
When the indication "voltage present"
does not appear, it is highly recommended
installing earthing equipment before work.
A voltage tester of relatively high internal
impedance, compared to the reference value
of 100 kΩ, may not permit to clearly indicate
the absence of operating voltage in case of
the presence of interference voltage.
When the indication "voltage present" appears
on a part that is expected to be disconnected
from the installation, it is highly recommended
confirming by another means (e.g. use of
an adequate voltage tester, visual check of
the disconnecting point of the electric circuit,
etc.) that there is no operating voltage on the
part to be tested and to conclude that the
voltage indicated by the voltage tester is an
interference voltage.
A voltage tester declaring two values
of internal impedance has passed a
performance test of managing interference
voltages and is (within technical limits)
able to distinguish operating voltage from
interference voltage and has a means to
directly or indirectly indicate which type of
voltage is present.
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