Ramps and alarms
Ramps
If a ramp rate was configured, the process reaches the setpoint
via a linear ramp.
The ramp rate is set within range 0 to 200
°
C with parameter
. The ramp function is disabled when the parameter
set
to 0.
Alarms
The alarm can be used for a minimum or maximum value moni-
toring of the process variable or of the control deviation.
Optionally, the first alarm signal can be suppressed, e.g. when
starting up a furnace and a minimum nominal value is monitored,
due to a low initial temperature. No alarm is signalled at this
stage, but signalling occurs when the temperature first exceeds
the minimum value and falls back to a value below the alarm set
point.
Timer (time alarm)
The alarm relay can also be configured for a timer function.
To do this, the value 12 or 13 is set for parameter
. A time
between 0 and 3600 min is preset for parameter
.
After switching on the supply voltage, the time function of the
alarm relay is activated. The timer starts when the process vari-
able has reached the setpoint. After the run out of the preset
time the alram relay is switched on (
= 13) in order to send
a signal or switch on a device. Alternatively the alram relay is
switched off (
= 12) after the run out of time in order to
switch off a device (e.g. even the power supply of the controller
itself).
Example
Fig. 6
Z-18817
The value for the ramp rate of the setpoint was set to 5
°
C/min
and a timer function was configured (
= 12,
= 15).
At the time t = 0 the control begins by connecting the supply
voltage. Since a ramp rate was set, the temperature increases at
a speed of 5
°
C/min to a setpoint of 125
°
C. On reaching the
setpoint, the timer is started. After expiry of the preset 15 mi-
nutes, alarm relay 1 opens and can then switch off a unit, in-
cluding for instance the controller itself.
By using the 2nd timer function (
= 13), the alarm relay
function can be inversed: the alarm relay initially remains open
and closes upon reaching the setpoint and after expiry of the
preset time.
Ramps and Alarms
13
