Precision Digital PD6310 - Manual (Page 57)

Model PD6210 & PD6310 Batch Controllers Instruction Manual
57
Relay Operation Details
Overview
The relays of the controller can serve two 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 in-
ternal relays and/or 4 external relays expansion module.
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 34.
Typical applications for alarms are low and high flow alarms or grand
total limit alarms. Note that rate alarms are only enabled during a batch-
ing 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 pro-
grammed state at controller power-up.
Fail-Safe Operation
The following table indicates how alarm relays behave based on the fail-
safe selection for each relay:
Fail-Safe
Selection
De-Energized State Energized State
Power Failure
NO NC NO NC
Off Open Closed Closed Open
Relays in de-
energized state
On Closed Open Open Closed
Relays in ener-
gized state
Note: NO = Normally Open, NC = Normally Closed. This refers to the
condition of the relay contacts when the power to the controller is off.