Helios Large Display Analog Input Batch Controller Instruction Manual
PD2-6210
44
Relay Operation Details
Overview
The relays of the controller can serve three roles, as batch control relays for single or multi-stage
batching, as rate, or grand total alarm, or as a sampling relay based on grand total or rate alarm.
These capabilities include front panel alarm status LEDs and 2 or 4 internal relays. The relays used for
batch control (total) are activated when the batching process starts, and deactivate when the batch total is
reached, minus any preclose amount programmed for batch (total) relays after the first.
For an example of batch control operation, see Batch Control Operation Example on page 26.
Typical applications for alarms are low and high flow alarms or grand total limit alarms. Note that rate
alarms are only enabled during a batching process, and deactivate when the processes is stopped.
The relays can also be set for sampling, where the relay will activate for a specific amount of time after a
certain grand total has been reached (ie: 2 second sample relay activation every 100 gallons batched).
There are three basic ways the relays can be used:
1. Batch Control (Total)
2. High or Low Alarms for Rate or Grand Total
3. Sampling (Based on Grand Total and Sample Time)
Relays Initialization
Batch control (total) relays will activate when the start function is enabled, such as when the START
button is pressed. Rate alarm relays will enable and initialize to their programmed states when the batch
process is started. Grand total alarm relays will initialize to their programmed state at controller power-up.
Fail-Safe Operation
The following table indicates how
the relays behave based on the fail-
safe selection for each relay:
Note: NO = Normally Open,
NC = Normally Closed.
This refers to the condition of
the relay contacts when the
power to the meter is off.
Front Panel LEDs
The LEDs on the front panel provide status indication for the following:
The controller is supplied with four alarm points that include front panel
LEDs to indicate alarm conditions. This standard feature is particularly
useful for alarm applications that require visual-only indication. The LEDs
are controlled by the set and reset points programmed by the user. When the display reaches a set point
for a high or low alarm, the corresponding alarm LED will turn on. When the display returns to the reset
point the LED will go off. Note that rate alarms are only enabled during a batching process, and
deactivate when the processes is stopped.
Latching relays, or relays with manual reset, are not recommended when using this controller for batch
control, as the manual reset will not be acknowledged during a batch process, when the rate alarms are
active. For information on latching and manual reset alarms, see the PD2-6200 instruction manuals
Fail-Safe
Selection
Non-Alarm State Alarm State
Power Failure
NO
NC
NO
NC
Off
Open
Closed Closed Open
Relays go to
non-alarm state
On
Closed
Open
Open
Closed Relays go to
alarm state
LED
Status
1
Alarm 1
2
Alarm 2
3
Alarm 3
4
Alarm 4
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