4.5
Alarm relay 1 hysteresis (deadband)
Display:
A1HY
Range:
0
to
9999
Default Value:
10
Displays and sets the alarm relay hysteresis limit for relay 1. To set a relay hysteresis value go to the
A1HY
function and use the
^
or
v
push buttons to set the value required then press
F
to accept this
value. The hysteresis value is common to both high and low setpoint values. The hysteresis value may be
used to prevent too frequent operation of the relay when the measured value is rising and falling around
setpoint value. e.g. if
A1HY
is set to zero the alarm will activate when the display value reaches the alarm
setpoint (for high alarm) and will reset when the display value falls below the setpoint, this can result
in repeated on/off switching of the relay at around the setpoint value. The hysteresis setting operates as
follows: In the high alarm mode, once the alarm is activated the input must fall below the setpoint value
minus the hysteresis value to reset the alarm. e.g. if
A1Hi
is to
50.0
and
A1Hy
is set to
3.0
then the
setpoint output relay will activate once the display value goes to
50.0
or above and will reset when the
display value goes below
47.0
i.e. at
46.9
or below. In the low alarm mode, once the alarm is activated
the input must rise above the setpoint value plus the hysteresis value to reset the alarm. e.g. if
A1Lo
is to
20.0
and
A1Hy
is set to
10.0
then the alarm output relay will activate when the display value
falls to
20.0
or below and will reset when the display value goes above
30.0
i.e at
30.1
or above. The
hysteresis units are expressed in displayed engineering units.
Example:
If
A1Hi
is set to
100
and
A1HY
is set to
10
then relay 1 will activate when the display value is
100
or higher and will reset at a display value of
89
or lower.
4.6
Alarm relay 2 hysteresis (deadband)
Display:
A2HY
Range:
0
to
9999
Default Value:
10
Displays and sets the alarm relay hysteresis limit for relay 2 which operates in the same manner as the
A1HY
function. See
A1HY
function for further description.
4.7
Alarm relay 1 trip time
Display:
A1tt
Range:
0
to
999.9
Default Value:
0.0
Displays and sets the alarm trip time in seconds and tenths of seconds. The trip time is common for
both alarm high and low setpoint values. The trip time provides a time delay before the alarm relay will
activate when an alarm condition is present. The alarm condition must be present continuously for the
whole trip time period before the alarm will activate. If the input moves out of alarm condition during
this period the timer will reset and the full time delay will be restored. This trip time delay is useful for
preventing an alarm trip due to short non critical deviations from setpoint. The trip time is selectable
over
0.0
to
999.9
seconds. To set a trip time value go to the
A1tt
function and use the
^
or
v
push
buttons to set the value required then press
F
to accept this value.
Example:
If
A1tt
is set to
5.0
seconds then the display must indicate an alarm value for a full 5 seconds before
relay 1 will activate.
18 of
LDRSMANADD-2.3-0
