Instruction Manual
ExTox Control Units Series ET-8D and ET-4D2
Page 27 of 39
Attention: For transmitters based on the measuring principle catalytic combustion and semi-
conductor the sensor signal might fall again into the measuring range due to the suppres-
sion of oxygen at very high concentrations of flammable gases. When using ExTox-
Transmitters safe measurement is ensured when configuring the channel fault as latching
(see 4.1). In case of Over-Scale of measuring range the indication of bar graph and meas-
ured value remain at a value above the end value of measuring range, even in case the
transmitter signal falls again.
The indication of bar graph and measured value are actualised if the Over-Scale of measur-
ing range is quit by pressing functional key F5 or F3 (AQUIT) (activated latching alarms
have then to be quit independently according to 5.3.).
In any way please check before quitting the alarm that the gas concentration is really below
the alarm levels again.
Status-LEDs
Channel Fault (yellow):
off
Alarm 1, 2, 3 (red):
on, for triggered alarms
Operation of Channel:
on, if channel activated
Operation:
on
Fault Control Unit:
off
Display
Bar Graph:
respective to 0 or end value of measuring range
Actual Value:
< 0 or > End Value of Measuring Range
Alarm A1, A2, A3:
1 for triggered alarms, otherwise 0
Fault F:
0 (or 1 for latching fault acc. to 5.5)
Relays ET-8D (for ET-4D2 in brackets)
K1 to K24 (K12):
triggered, if alarm condition contains activated alarms.
Fault Control Unit K25 (K13): closed
Maintenance K26 (K14): closed
5.5
Channel Fault
The input current of the transmitter is outside the limits fixed in the system parameters
(4.8.2), that means the (un-processed) transmitter input current is below I
min
or above I
max
.
Reason for that might in general be a transmitter fault, interruption of transmitter power
supply, interruption or short circuit of transmitter cable.
If the channel fault is configured as latching, it has to be reset manually in case the alarm
condition is no longer available.
Series ET-8D: for that purpose the bar graph and detail indication has to be activated (see
Chapter 3). Now the corresponding channel has to be selected on the display and then the
fault F to be reset by means of the functional keys F3 (<AL) or F4 (AL>). The fault can now
be cleared by means of the functional key F5 (AQUIT).
Series ET-4D2: for that purpose the bar graph and detail indication has to be activated. Now
the corresponding channel has to be selected on the display by using functional key F1
(<CH>) and then the fault to be reset by means of the functional key F2 (<AL>). By means
of functional key F3 (AQUIT) the fault can now be cleared.
In case of setting the parameter AQUIT=OFF (see 4.8.7) it is only possible to quit the fault
if you have released access level 2 or 3 before.
Attention: In application for explosion protection the channel fault has to be appointed to
minimum one relay, for example in a collective message. In our standard configuration
(4.2) relay 24 (ET-8D) or relay 12 (ET-4D2) is engaged correspondingly
