Function
24
IRDH275_D00122_02_M_XXEN/10.2016
3.5 Additional functions IRDH275B
Current output for external measuring instrument
The current output of IRDH275B provides 0(4)…20 mA. The current output is
galvanically isolated from the device electronics and the RS485 interface. The
ISO SETUP menu, on page 50, allows to switch over between 0…20 mA and
4…20 mA.
Real-time clock
The real-time clock serves as a time base for the memory and self test func-
tions. At first, the correct time and date must be set in the menu "ISO AD-
VANCED". If time and date are not set, a „C“ (clock) is flashing in the standard
display. In the event of a supply voltage failure, time and date will be stored
for at least thirty days.
If the 24 h test is activated in the "ISO ADVANCED" menu, a special time of day
can be selected for the execution of the self test in the menu "TEST: 12:00".
Then a self test will be started automatically once a day exactly at the preset
time. If the 1 h auto test has been selected, the self test is automatically carried
out every full hour.
Interconnected IT systems
When using ISOMETERs
®
in IT systems, make sure that only one active
ISOMETER
®
is connected in each interconnected system. If IT systems are inter-
connected via coupling switches, make sure that ISOMETER
®
s not currently
used are disconnected and deactivated via a control system. IT systems cou-
pled via diodes or capacitances may also influence the insulation monitoring
process. Hence, also in this case a central control of the different ISOMETER
®
s
is required.
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