24
NOTE
Since the flash rate increases as the voltage
increases, different flash rates are clues to the
voltage levels that are present. Therefore, a
careful observation of the flash rate serves as
an additional check for the presence of
improper voltages due to incorrect system
connections.
Testing for Absence of Voltage Before Starting Work –
LED Phasing Tester
Frequently, when a line is separated from the source of supply but not yet
grounded there is a relatively high voltage present on the line, resulting
from induction due to neighboring lines which are still live. A single-pole
voltage detector used under these conditions will give a positive indication
which may give the impression that the circuit has not been broken.
Using the voltage-adjusting knob on the LED phasing tester resolves this
difficulty. Because there is a large difference between the normal service
voltage and the induced voltage, when the tester is set to the service
voltage, it will only light when the line is effectively connected to the source
of supply. This check having been made, it is then possible, by adjusting the
voltage-regulating switch to minimum, to find out if the circuits are live at
an induced voltage (down to the threshold of sensitivity of the indicator,
approximately 2000 V).