Watlow Series SD PID Profiling Controller - Manual (Page 72)

Wa t l o w S e r i e s S D • 7 0 • C h a p t e r 1 2 F e a t u r e s
ing is done only at the zero cross of the ac line, which
helps reduce electrical noise (RFI).
Variable time base should be used with solid-state
power controllers, such as a solid-state relay (SSR) or
silicon controlled rectifier (SCR) power controller. Do not
use a variable time base output for controlling electrome-
chanical relays, mercury displacement relays, inductive
loads or heaters with unusual resistance characteristics.
The combination of variable time base output and a
solid-state relay can inexpensively approach the effect of
analog, phase-angle fired control.
You must select the AC Line Frequency, 50 or 60 Hz.
100 percent output
10 ON, 0 OFF
50 percent output
3 ON, 3 OFF
66 percent output
6 ON, 3 OFF
Single Set Point Ramping
(static set point version only SD_C- _ _ _ _- _ _ _ _)
Ramping protects materials and systems that can-
not tolerate rapid temperature changes. The value of the
ramp rate is the maximum degrees per minute or hour
that the system temperature can change.
Select Ramping Mode [``rP] (Setup Page):
[`OFF] ramping not active.
[`Str] ramp at startup.
[``On] ramp at startup or when the set point changes.
Select whether the rate is in degrees per minute or
degrees per hour with Ramp Scale [rP;Sc] (Setup Page).
Set the ramping rate with Ramp Rate [rP;rt] (Setup
Page).
Set Point
Time
Temperature
Temperature reaches Set Point quickly
Set Point
Time
Temperature
Temperature ramps to Set Point at a set rate
degrees
per minute
Alarms
Alarms are activated when the process value or tem-
perature leaves a defined range. A user can configure
how and when an alarm is triggered, what action it takes
and whether it turns off automatically when the alarm
condition is over.
Configure alarm outputs in the Setup Page before set-
ting alarm set points.
Process or Deviation Alarms
A process alarm uses one or two absolute set points to
define an alarm condition.
A deviation alarm uses one or two set points that are
defined relative to the control set point. High and low
alarm set points are calculated by adding and/or sub-
tracting offset values from the control set point. If the
set point changes, the window defined by the alarm set
points automatically changes with it.
Select the alarm type with the Setup Page param-
eters. View or change process or deviation set points with
the Operations parameters.
Alarm Set Points
The alarm high set point defines the process value or
temperature that will trigger a high side alarm. It must
be higher than the alarm low set point and lower than
the high limit of the sensor range.
The alarm low set point defines the temperature that
will trigger a low side alarm. It must be lower than the
alarm high set point and higher than the low limit of the
sensor range.
View or change alarm set points with the Operations
parameters.