11 96VTR Ver. 2.0 11/99
Control
Relay
Alarm
Relay
AC
Load
Example of Wiring Alarm and Control Relays in Series
Meter Contacts
Figure 4
16
18
12
13
19
20
The controller's output percent will now appear on the SV display preceded by an 'H"
for Heating or a 'C' for Cooling (depending upon how the action of the controller is
configured under the parameter 'act'). The 'MA' Manual status LED will also illuminate
and flash. To manually adjust the controller's output, use the UP and DOWN arrow
keys. For controllers using two control outputs (primary and secondary), the SV display
will automatically toggle between outputs 1 and 2. To return to normal operation, press
and hold the RETURN key until the 'MA' LED extinguishes. To Lock this feature, press
and hold the UP and RETURN keys until the display flashes. While locked, the Manual
Mode is inaccessible.
11. RAMP-TO-SETPOINT AND EVENT/SOAK TIMER FUNCTIONS
The Extech 96VTR controller operates as a fixed setpoint controller. However, the
controller offers several advanced features which can enhance your application. These
include Ramp-to-Setpoint and Event/Soak Alarm/Timers.
11.1 Ramp-to-Setpoint ('rAmP' Parameter)
To limit the rate at which the controller allows the process (PV) to move towards
setpoint (SV), enter a limit value in degrees (or other units) per minute in the 'rAmP'
parameter. The programmable limit ranges from 0.0 to 100.0 units per minute. The
controller will automatically adjust the controller's outputs to maintain the desired limit
programmed by the user. A setting of zero defeats the Ramp-to-Setpoint function.
11.2 Soak Timer Function (for use with Alarm 1 only)
The Alarm 1 Soak Timer allows the process to ramp to a setpoint and remain (Soak) at
that setpoint for a user-programmable period of time. Set the "A1Fu" parameter to
either '10' (Soak ON-TIMER) or '11' (Soak OFF-TIMER) depending upon the
application (See
Appendix A, Table
IV, for the
difference between
ON- and OFF-
TIMERS). Set the
Soak time in
parameter 'timE' in
the First
Programming Level.
The Output and
Alarm Relays must
be wired in series
so that the Alarm
relay can switch the control relay at the appropriate times (refer to Fig. 4). For
example, when a setpoint of 500
o
F is reached, the Soak time (programmed by the user
under parameter 'timE") begins to countdown. After the desired Soak time has elapsed,
the Alarm relay switches thereby switching the Control relay.
11.3 Event Timer (Alarm 1 relay only)
Alarm relay 1 can be programmed to switch state at desired times in a process. This is
accomplished by first setting the alarm function in parameter "A1Fu" to either an
EVENT-ON or EVENT-OFF Timer (See Appendix A, Table IV, for the difference
between ON- and OFF-TIMERS). Next, pick a count-down time. The relay timer will
start counting down once the PV equals the SV. The duration of the count-down is set
by the user at parameter "timE".
Application example: While maintaining a certain temperature for 4 hours, an event is
to take place 2 hours into the process. The event, in this example, is the controller's
alarm relay activating a pump. To do this, set the alarm function to an EVENT-ON
