Soak And Event Timers - Extech Instruments 48VTR User Manual

Soak and Event Alarm Timers
In addition to Alarm functions, the Alarm Relays can be used as Timers. SOAK Timers and
EVENT Timers are explained below:
Soak Timer
The Soak Timer allows the process to ramp to a setpoint and remain (Soak) at that
setpoint for a user-programmable period of time. Follow the steps below:
1. Set the 'A1Fu' parameter to either '10' (Soak ON-TIMER) or '11' (Soak OFF-TIMER);
refer to the Table in Appendix A for the difference between ON and OFF Timers).
2. Set the desired Soak time in parameter 'timE' in the 1
3. 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 diagram below).
4. Now when the setpoint is reached, the Soak time begins to countdown (ALM status
LED will flash while the counter elapses). After the Soak time has elapsed, the
Alarm relay trips thereby switching the Control relay circuit.
Wiring the Control Output through the Alarm
In the diagram, the External Control Device
uses the same AC power that powers the 48VTR.
For devices that require a different AC source or for
devices that require DC power, an alternate wiring
Event Timer
An Event Timer trips the Alarm relay at a desired point in a process. Follow the steps
below:
1. Set the alarm function parameter 'A1Fu' to either an EVENT-ON or EVENT-OFF
Timer (refer to Appendix 'A' for the difference between ON and OFF Timers).
2. Select a countdown time in parameter 'timE' in the 1
3. The timer will begin counting when the PV equals the SV. After the counter elapses,
the alarm relay switches.
Event Timer Example
Example process description: An oven is controlled by a 48VTR to maintain a
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.
Step by step instructions for above example
1. Wire the Alarm relay in series with the power to the pump.
2. Set parameter'A1Fu' in Menu Level 3 to an EVENT-ON Timer (selection 8).
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3. Set the 1 Menu Level parameter 'time' to 120 minutes (2 hours).
4. When the controller is powered the alarm relay will be OFF, when the PV = SV the
relay remains OFF but the timer begins to countdown, and after 2 hours the relay
will turn ON permitting the 'Event' to take place.
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External Control Device
6 7 8 9
4 5
scheme must be employed.
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23 Model 48VTR - Version 5.0 – January 2006
Menu Level.
Menu Level.