Tek-Trol TEK-LCD 7800A-0L1, Инструкция по эксплуатации, Страница: 26 / 36

3.8.1 Alarm Output (
OUTPUT
)
The Tek-LCD 7800A-0L1 is equipped with an NPN open collector output that may be set up for
high or low alarm trip point based on the level display (
LEVEL ) or the volume scale ( VOLUME ). The
output may be disabled by selecting
OFF
.
When the alarm is enabled for level and the alarm set point has been reached, the level display
will flash, accompanied by the bottom display alternating between normal display and HI
ALRM
or LO ALRM , depending on whether a high alarm or a low alarm has been set. A tank height
indicator segment will flash at the level to which the alarm is set while the level indicator is at
or above the alarm point.
When the alarm is enabled for volume and the alarm set point has been reached, the bottom
display will flash, alternating between its normal display and HI
ALRM or LO ALRM , depending on
whether a high alarm or a low alarm has been set. To set a high alarm, program the set point
above the reset point. To set a low alarm, program the set point below the reset point.
To acknowledge an alarm, press the
ENTER button once for acknowledge prompt and a second
time to confirm. Acknowledging an alarm will turn off the alarm output and stop the display
from flashing. The
HI or LO symbol will remain until the alarm condition is cleared.
The alarm status will show on the display even if the output is not wired.
3.8.2 Input Signal Filter ( FILTER )
The noise filter is available for unusually noisy signals that cause an unstable process variable
display. The noise filter averages the input signal over a certain period. The filter level can be set
to low (
LO ), medium ( MED ), high ( HI ), or off ( OFF ). The higher the filter setting, the longer the
averaging time and so the longer the display may take to find its final value.
The filter contains a noise filter bypass feature so that while small variations in the signal will be
filtered out, large, abrupt changes to the input signal are displayed immediately.