DayTronic 3500 Series, Instruction Manual

Page: 54 / 122

The reason for setting up a HIGH HYSTERESIS WINDOW is to prevent low-
level signal noise from toggling control outputs on and off when the data
reading is in the neighborhood of the HIGH LIMIT value.
A "HIGH VIOLATION" will be triggered only when the data reading enters the
"GREATER THAN ZONE" by exceeding the current "HIL" value. This is what
happens at time t
1
in the above figure. At time t
2
, the data falls back to the "OK
ZONE." If there were no hysteresis window—and assuming that this is a NON-
LATCHING limit—the "HIGH VIOLATION" would cease to occur as soon as the
live data reading became less than "HIL" at time t
2
. In this case, however, the
limit status continues to be evaluated as "HIGH VIOLATION" until such time as
the data reading becomes less than the lower threshold of the HIGH HYS-
TERESIS WINDOW—which is what happens at time t
3
. At this point, the limit
status is evaluated as "OK."
To change the HIGH HYSTERESIS value, use the NUMERIC BUTTONS as
explained in Section 1.e to modify the displayed number. REMEMBER: This
number expresses a PERCENTAGE OF THE EXISTING "m" COEFFICIENT. If
you don't need a hysteresis window, just enter a value of "0."
g. When the desired HIGH HYSTERESIS value appears, press ENTER to return
to the "HIHYS" display . Then press LIMIT again. The unit will display "HILAT"
(for "HIGH LATCH"):
h. To display the current HIGH LATCH status, press ENTER . If you don't want to
display the HIGH LATCH, press LIMIT again and proceed to Step k.
i. If the HIGH LATCH status is OFF , it means that the limit is NONLATCHING: the
"HIGH VIOLATION" status will cease to occur as soon as the data reading
leaves the "GREATER THAN ZONE." If the HIGH LATCH status is
ON , it means
that the limit is LATCHING: once a "HIGH VIOLATION" is triggered, this condi-
tion will remain in effect until it is reset by means of an "UNLATCH" command
3.16
3
S
ETUP
: I
NSTRUMENT
C
ONFIGURATION
3.a C
ONFIGURING
T
HROUGH THE
F
RONT
P
ANEL
HIL
LOL
Greater Than Zone
Less Than Zone
t
1
t
2
t
3
HI Hysteresis
Window
LO Hysteresis
Window
OK Zone
"Live" Data Reading
Fig. 19 High and Low Hysteresis Windows