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9.3.8 Alarm output status: no.nc
This function allows the alarm output to be
open or closed in the alarm condition. When
deciding which is required, care must be
taken to ensure that the alarm output is fail
safe. See Fig 9.
CAUTION
When the 4/20mA supply is removed
both alarm outputs will open
irrespective of conditioning.
Therefore for fail safe operation both
alarm outputs should be programmed
to be open in the alarm condition.
To check or change the alarm output status
select 'no.nc' from the alarm menu and
press P to reveal the current setting. The
function can be changed by pressing the Up
or Down button followed by the E button to
return to the alarm menu.
9.3.9 Hysteresis: HStr
Hysteresis is only available on rate alarms.
During programming hysteresis is shown in
the units of rate the BA358C has been
calibrated to display.
To adjust the hysteresis, select 'HStr' from
the alarm menu and press P which will
reveal the existing figure. Each digit can be
adjusted using the Up and Down push-
buttons, and the P button to move to the
next digit. When the required hysteresis has
been entered, press E to return to the alarm
menu.
e.g. A BA358C calibrated to display a flow
of 0 to 5000, with a high alarm set at 4000
and hysteresis of 100 will perform as follows:
High alarm will be activated when flow
equals or exceeds 4000, but will not
reset until the flow falls below 3900.
Fig 12 Alarm programme menu
