5.10 ALARM
There is a independent alarm available by adjusting the alarm special
function A1SF and A2SF. The following descriptions of this section are
based on Alarm 1.
* Latch Alarm: A1SF =
When selected, the alarm output and indicator latch as the alarm occurs.
The alarm output and indicator will be energized even if the alarm condition
has been cleared unless the power is shut off.
* Hold Alarm: A1SF =
When selected, in any alarm mode, prevents an alarm on power up. The
alarm is enabled only when the process value reaches setpoint value
(SV).
Example: Hold function used with deviation low alarm
* Lach & Hold Alarm: A1SF =
When selected, in any alarm mode, prevents an alarm on power up. The
alarm is enabled only when the process value reaches setpoint value
(SV). Thereafter, the alarm acts as a latch alarm described above.
* Hysteresis (AHY1) adjustment
Example: No special function used with deviation high alarm,
SV = 100 °C, ASP1 = 10 °C, AHY1 = 4 °C
5.11 VIEWING THE OUTPUT PERCENTAGE POWER
Selecting the Tool Programs until the HAND CONTROL is obtained.
Press scroll key, the display will show the process value and the display
will show the percentage power of output 1 such as . To view the
cooling output, press scroll key again. The lower display will show the
percentage power of alarm 2 such as , if alarm 2 is reconfigured as
cooling output (A2SF = COOL). If alarm 2 is configured as alarm, the
percentage power is invalid and should be ignored.
The range of the output percentage power is within 0 and 100 (%). If an
on-off control is selected, only 0 and 100 are displayed. For a proportional
control, the output percentage power represents the duty cycle of the
output ON-state.
Example: is viewed with cycle time CYC = 10 sec.
The output 1 act as follows:
0
10
20
30
40
50
60
70
80
25
50
75
100
125
150
C
t (minutes)
Process Value
4 sec.
6 sec.
OFF
ON
OUTPUT
Time
5.12 MANUAL CONTROL
Following the procedure as in section 5.11, then press and hold the scroll
key for 3.2 seconds and release, the controller will enter the manual
control mode. The display begins to flash. The output percentage power
can be adjusted by using up or down keys. Note that for an on-off control
with PB = 0, the manual control is not allowable to be used. An error
message will be shown in the display.
The manual control is used during:
* Teaching the process
* The controller fails
The manual control is an open loop control The process may rise
to a dangerous value (temperature). Special attention to the process has
to be given to prevent a system damage.
5.13 RAMP & DWELL
The controller can be configured to act as either a fixed setpoint controller
or as a single ramp controller on power up. This function enables the user
to set a predetermined ramp rate (RAMP) to allow the process to gradually
reach setpoint temperature thus producing a " soft start " function.
A dwell timer is incorporated within the controller and the alarm 1 can be
configured by setting A1SF = or to provide either a
dwell function or a soak function to be used in conjunction with the ramp
function.
5.13.1 Ramp Function
If the ramp function is selected, the process will increase or decrease at
a predetermined rate during initial power up, or with setpoint changes/
process variations.
The ramp rate is determined by the " RAMP " parameter which can be
adjusted in the range 0 to 55.55 °C / minute ( 99.99 °F / minute). The ramp
rate function is disabled when the " RAMP " parameter is set to " 0 ".
In the example below the " RAMP " is set to 5.00 °C / minute, power is
applied at zero time and the process value climbs to the 125 °C setpoint
over a period of 20 minutes. This process temperature is held until the
setpoint value is changed to 150 °C at 40 minutes. The process value then
climbs to the new setpoint over a period of 5 minutes and the new setpoint
is held. At 70 minutes the setpoint value is decreased to 75 °C and the
process value falls to the new setpoint over a period of 15 minutes.
: Alarm on
No special function: A1SF=
SV
SV+ASP1
*
Without
hold alarm
alarms on
power up
SV
SV
SV
SV+ASP1
*
With hold alarm
No alarm
on power up
Alarm
enabled
Alarm
operates
normally
there after
*
Full scale
high alarm
A1MD
ASP1
*
Full scale
low alarm
A1MD
ASP1
SV+ASP1+ 1/2AHY1
SV+ASP1
SV+ASP1- 1/2AHY1
Below 108 C
alarm off
Below 112 C
alarm off
*
*
*
Above 112 C
alarm on
Above 112 C
alarm on
112
110
108
Above 108 C
alarm stays on
112
110
108
Below 108 C
alarm off
112
110
108
Process proceeds
SV
SV+ASP1
*
Deviation
high alarm
A1MD
SV
SV+ASP1
*
Deviation
low alarm
A1MD
(ASP1 negative)
SV
*
*
Deviation band
high alarm
A1MD
SV- ASP1
SV+ ASP1
SV
*
*
Deviation band
low alarm
A1MD
SV- ASP1
SV+ ASP1
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