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HA20 2-Channel Controller
Figure 2-4. Alarm Setup Menu
• Set Point is entered in engineering units and determines
the value at which the alarm trips. For example, if a channel
monitors 0-50 ppm H
the correct entry is 10.00. A one percent deadband prevents
alarm chatter. This means after tripping an alarm the input must
move at least 1% of full scale back through the setpoint for the
alarm to auto reset.
• The ON Delay / OFF Delay entries allow ON and OFF time
delays affecting how long the trip-point must be surpassed
before an alarm event transition occurs. ON delays are limited
to 10 seconds while OFF delays may be as long as 120
minutes. Delays are useful in many applications to prevent
nuisance alarms and unwanted cycling into and out of alarm
conditions.
• Low Trip is set to NO to increase alarms or YES to decrease
alarms, which determines if the alarm activates upon exceeding
or falling below the set-point.
• Latching determines either manual or automatic alarm reset
operation. YES requires a manual Alarm Reset to unlatch the
alarm even though an alarm condition no longer exists. YES
also causes this alarm's common relay, front panel LED, and
optional discrete relay to latch. NO allows all outputs for this
alarm to automatically reset after the alarm condition clears.
Discrete LED indicators on the front panel indicate the status of each
HA20 Technical Manual
S and the desired alarm level is 10 ppm,
2
alarm. Any new alarm event causes the associated LED to flash until
an Alarm Reset occurs causing an acknowledged steady on condition.
Operators should recognize new alarms by a flashing LED. Alarm
Reset also acknowledges, or deactivates, audible devices driven by
the AUDIBLE ALARM option connector J2 (see
2.2.4 Using the Configure Menu to Define Channel
The next menu option, after the Alarm Setup option, is Configure.
It allows setting Name and EUNIT fields, defining the measurement
range (Zero and Span), how many decimal points of resolution the
reading will have and whether the channel is active (Figure 2.5).
Figure 2-5. Configure Menu - Define Channel
Name / Eunits ASCII Data Fields
The first two items in this menu, Name and EUNIT, are for entering
the 10 character channel Name and engineering unit ASCII fields.
Name should describe the channel's data in user terminology such as
tag # or other description. Eunits should define the units of measure
for what this channel is to display. Several standard Eunits fields are
available by pressing Edit but if these are inappropriate, a CUSTOM
field allows editing of each character. Section 2.2 describes how to
modify these fields using the keypad.
2-4
Figure
3.2)
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