West Control Solutions DataVU 7 - Manual (Page 128)

18 Configuration - Groups
128
Channel 1 plus the positive tolerance and minus the positive hysteresis for the
alarm to be canceled again. The value for the “positive hysteresis” can only be
entered as a positive value.
Negative
hysteresis If a negative tolerance infringement has occurred, the present measurement
from Channel 2 — 6 first has to rise above the measurement from Channel 1
plus the negative tolerance and plus the negative hysteresis for the alarm to be
canceled again. The value for the “negative hysteresis” can only be entered as
a positive value.
Example The principle of initiating an alarm is the same as for the alarm configuration of
the individual analog channels.
Measurement (Channel 1) = 21°C
Measurement (Channel 2) = 21°C, tolerance band comparison is active.
Positive tolerance = 10°C
Positive hysteresis = 2°C
An alarm occurs if the present measurement (Channel 2) goes above 31°C.
The alarm is canceled if the present measurement (Channel 2) falls below
29°C.
Measurement (Channel 1) = 21°C
Measurement (Channel 2) = 21°C, tolerance band comparison is active.
Negative tolerance = -10°C
Negative hysteresis = 2°C
An alarm occurs if the present measurement (Channel 2) falls below 11°C.
The alarm is canceled if the present measurement (Channel 2) goes above
13°C.
In the example illustrated, Channel 1 is constant and Channel 2 alters its
measurement. However, this must not necessarily be so. It can also happen
that Channel 1 changes, or even that both channels change.
(1) (2)
(3) (3)
alarm on
alarm off
(1) = Negative alarm
(2) = Positive alarm
(3) = Hysteresis