Instruction Manual
ExTox Control Units Series ET-8D and ET-4D2
Page 21 of 39
4.8.2
Inputs 4…20 mA
Access Level to perform changes of the parameter settings: 3
Menu Text
Selection
Function
Hysteresis
0 % to 20 %
Fixes the alarm hysteresis in percent of the end value of
measuring range. A non latching alarm expires only when
it is around the value of hysteresis below the alarm level.
This function serves for prevention of permanent repeat-
ing of alarm triggering due to slight variations of meas-
ured values around the alarm level.
Example: Measuring range 100 ppm, Hysteresis 3 %,
Alarm level 10 ppm. The alarm does not expire until 7
ppm is under run.
Standard setting: 0 %
Attention: combination of low alarm levels with too high
hysteresis values may lead to a very late reset or even
non-reset of alarms.
I
min
1.0 mA to
3.0 mA
Fixes the level at which a channel fault is indicated by
means of the transmitter input current in case of under-
run. The setting has to be chosen that way that fault con-
ditions of connected transmitters can be recognized safe-
ly. Therefore the value has to higher than all transmitter
output currents indicating fault conditions. Please pay at-
tention to the remarks in the Transmitter Instruction
Manual.
Standard setting for ExTox-Transmitters = 1.5 mA
I
max
21.0 mA to
24.5 mA
Fixes the level at which a channel fault is indicated by
means of the transmitter input current in case it is ex-
ceeded.
Standard setting for ExTox-Transmitters = 22.5 mA
NPC
0 to 5 %
The attenuation of the zero point can be set. In the range
0 to + NPC of the end value of measuring range the value
is indicated on 0. In the next range up to + 2·NPC of the
end value of measuring range a smooth approach to the
linear calibration curve will take place, which is valid from
+ 2 NPC on. The negative range is treated inversely in the
same way.
By this slight fluctuations in zero point can be suppressed
in the indication without changing the indication perfor-
mance as far as the alarm levels are concerned. Please
note that the alarm levels should not be in the range up
to + 2·NPC of end value of measuring range.
Standard setting: 0 %, i. e. deactivated.
Delay
A1, A2, A3, F
0 s to 60 s
A triggering delay can be adjusted for the alarm levels
and transmitter fault.
Standard setting: 0 s
