Function
13
TGH1361en/11.2009
message, provided that the currently displayed insulation resistance is at
least 25% above the actual response value when the reset is carried out. The
fault memory behaviour can also be set in the "ISO SETUP" menu, by select-
ing the sub menu Memory: on/off.
The connections for external kΩ display supplied by the current output
0...400 µA or 0/4...20 mA (IRDH275B) at M+/M- are galvanically isolated.
*) measuring principle "adaptive measuring pulse", a measuring
principle developed by BENDER (European Patent: EP 0 654 673 B1).
Self test
A self test can be carried out manually using the TEST button or automatical-
ly. In order to guarantee high functional reliability, the A-ISOMETER®
IRDH275 provides comprehensive self test functions. After switching the
supply voltage on, all internal measuring functions, the components of the
process control such as data and parameter memory as well as system and
earth connections are checked using the self test functions. The progress of
the self test is indicated on the display by a bar graph. Depending on the
conditions in the IT system to be monitored, the self test is running for
15...20 seconds, then the message "Test ok!" appears on the LC display for
approximately 2 seconds. Then the device returns to normal measuring
mode and the current measuring value is displayed after the expiry of the
measuring time.
When a device error or connection fault is found, the message "!Error!" ap-
pears on the display, the device fault LED lights up, the relay K2 (21-22-24)
switches and the respective fault message (see table) is indicated. If such a
device fault occurs, a self test is started again every minute. If no more mal-
function is detected, the fault message is deleted automatically and the
device fault LED extinguishes.
During operation, the self test function can be started by pressing the TEST
button (internal or external). The self test can also be started automatically
every hour or every 24 hours by selecting "ISO ADVANCED: Autotest" menu.
The alarm relays Alarm1/2 only switch after starting the self test function by
pressing the TEST button, that means if an automatic self test has been se-
lected, the alarm relays do not switch.
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