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10.4.4 Alarm selection: ALr1 or ALr2
As shown in Fig 12, each of the two alarms has an
identical set of sub-functions enabling each alarm to
be independently conditioned. ‘ALr1 provides access
to the alarm 1 sub-functions and ‘ALr2’ provides
access to the alarm 2 sub-functions. The following
sections 10.4.5 to 10.4.11 describe each of these
sub-functions in detail
10.4.5 Alarm enable: EnbL
This sub-function allows the alarm to be enabled or
disabled without altering any of the alarm
parameters. To check or change the sub-function
select 'EnbL' from the alarm sub-menu using the
▼
or
▲
button and press
P
which will reveal the current
setting. The function can be changed by pressing the
▼
or
▲
button followed by the
E
button to enter the
selection and return to the ‘EnbL’ prompt in the alarm
menu.
10.4.6 Setpoint adjustment: SP1
The setpoint of each alarm relates to the transmitter
digital display and may be positioned anywhere in the
transmitter display range.
To adjust the setpoint select 'SP1' from the alarm
menu and press
P
which will reveal the existing alarm
setpoint with one digit flashing. The flashing digit
may be adjusted using the
▼
or
▲
push button and
the
P
button to move control to the next digit. When
the required setpoint has been entered press
E
to
enter the new setpoint and return to the ‘SP1’ prompt
in the alarm menu.
Note:
If, when configured for a voltage or resistance
input the displayed decimal point has been set to
autorange, it may be necessary to manually position
the decimal point before adjusting ‘SP1’ or ‘SP2’.
This can be achieved by repeatedly operating the
P
button until the activated decimal point flashes, the
decimal point can then be positioned using either the
▼
or
▲
button. Pressing the
P
button again will
return control to one of the digits.
10.4.7 Alarm function: Hi.Lo
Each alarm can be independently conditioned as a
high or low alarm. To check or change the alarm
function select 'Hi.Lo' from the alarm menu using the
▼
or
▲
button and press
P
to reveal the current
setting. The function may be changed by pressing
the
▼
or
▲
button, pressing the
E
button will enter
the setting and return the display to the ‘Hi.Lo’ prompt
in the alarm menu.
10.4.8 Alarm output status: no.nC
This sub-function allows the alarm output to be open
or closed in the non-alarm condition. When deciding
which is required, care must be taken to ensure that
the alarm output is fail safe. See Fig 11.
‘no’
Alarm output open in non-alarm condition
‘nC’ Alarm output closed in non-alarm condition
CAUTION
When the transmitter supply is
removed both alarm outputs will open
irrespective of conditioning. Therefore
for fail safe operation both alarm
outputs should be conditioned to be
open in the alarm condition.
To check or change the alarm output status select
'no.nC' from the alarm menu using the
▼
or
▲
button
and press
P
to reveal the current setting. The
function can be changed by pressing the
▼
or
▲
button followed by the
E
button to enter the setting
and return to the ‘no.nC’ prompt in the alarm menu.
10.4.9 Hysteresis: HStr
Hysteresis is shown in the same units as the
transmitter digital display.
To adjust the hysteresis, select 'HStr' from the alarm
menu using the
▼
or
▲
button and press
P
which will
reveal the existing figure with one digit flashing. The
flashing digit can be adjusted using the
▼
or
▲
push
buttons, and the
P
button to move control to the next
digit. When the required hysteresis has been
entered, press
E
to enter the new setting and return
to the ‘HStr’ prompt in the alarm menu.
e.g. A BA474ND transmitter with a high alarm set at
90.0 and hysteresis of 10.0 will perform as follows:
The alarm will be activated when the display
equals or exceeds 90.0, but will not be
deactivated until the display falls below 80.0.
Note:
If, when configured for a voltage or resistance
input the displayed decimal point has been set to
autorange, it may be necessary to manually position
the decimal point before adjusting ‘HStr’. This can be
achieved by repeatedly operating the
P
button until
the activated decimal point flashes, the decimal point
can then be positioned using either the
▼
or
▲
button. Pressing the
P
button again will return
control to one of the digits.