22
Fig 10 Equivalent circuit of each alarm output
Fig 11 Typical alarm application
8.3.2 Programming and adjustment
When a BA558C is supplied with alarms the main
programme menu is extended as shown in Fig 12.
The two alarm functions appear between the 'C--P'
and the 'SCALE-t' functions, and each alarm may
be programmed as a rate or a total alarm. Both
alarms may be conditioned as rate alarms or both
as total alarms, or one rate and one total alarm
may be selected.
For simplicity Fig 12 only shows the programmable
functions for alarm AL1. Alarm 2 and the total
options are identical except that the total alarms do
not have hysteresis.
The following table summarises each of the alarm
programme functions and includes a cross
reference to more detailed information. Again
only the functions on alarm AL1 are listed.
Summary of programmable alarm functions
Display
Description of function
'EnbL'
Alarm enable
Enables or disables the alarm function
without changing the alarm parameters.
See section 8.3.3
'tYPE'
Type of alarm
Defines whether the alarm operates on
the rate or total display.
See section 8.3.4
'SPr1'
Alarm setpoint 1
or
Adjusts the alarm setpoint . The
'SPt1'
alarm is activated when the rate or total
display equals the setpoint.
See section 8.3.5
'HI.LO'
Alarm function
Defines whether the alarm has a high or
low function
See section 8.3.6
'no.nc'
Normally open or normally closed
output
Determines whether the single pole
alarm output is open or closed in the non
alarm condition.
See section 8.3.7
'HStr'
Hysteresis
Adjusts the alarm hysteresis. Only
available on rate alarms.
See section 8.3.8
'dELA'
Alarm delay time
Adjusts the delay between the display
equalling the setpoint and the alarm
output being activated.
See section 8.3.9
'SIL'
Alarm silence time
Defines the time that the alarm output
remains in the non-alarm condition
following acceptance of an alarm.
See section 8.3.10
'AcSP'
Access setpoint
Sub-menu which enables direct access
to the alarm setpoints from the display
mode and defines a separate security
code.
See section 8.3.11
