USER'S GUIDE ____________________________________________________________________
42 __________________________________________________________________ M210543EN-F
Relay Controls
PWD22/52 has three open collector relay controls that are controlled by
software using the alarms limits set in the CONF command.
The three PWD22/52 relay controls can be driven by the visibility limits.
The third relay control can also be driven by the hardware status.
- ALARM LIMIT 1
- ALARM LIMIT 2
- ALARM LIMIT 3
These are visibility alarm limits of 10-minute average. Limit value 0
indicates that this limit is not used. The three visibility limits are
independent of each other, which means that ALARM LIMIT 1 sets the
limit for RELAY CONTROL 1 only. ALARM LIMIT 2 sets the limit for
RELAY CONTROL 2 only and so on. For example, RELAY CONTROL
1 is pulling whenever visibility is lower than ALARM LIMIT 1. See
Table 7 and Table 8 below.
- RELAY ON DELAY
- RELAY OFF DELAY
The visibility alarm conditions must last the corresponding time in
minutes specified in RELAY ON/OFF DELAY parameter before the
relay control changes. The default delays are five minutes.
Below is a table with a control logic example of relay controls 1 and 2
when the third relay control is driven by hardware status.
Table 7 Control Logic of Relay Controls 1 and 2
Corresponding Visibility Conditions
When visibility is higher than LIMIT 1 and LIMIT 2.
When visibility is lower than LIMIT 1 but higher
than LIMIT 2.
When visibility is lower than LIMIT 1 and LIMIT 2.
The table below shows a control logic example of relay controls 1 and 2
and 3 when all the relay controls are driven by visibility limits.
Table 8 Control Logic of Relay Controls 1, 2, and 3
Corresponding Visibility Conditions
When visibility is higher than all the limits.
When visibility is lower than LIMIT 1 but higher than
LIMIT 2 and LIMIT 3.
When visibility is lower than LIMIT 1 and LIMIT 2 but
higher than LIMIT 3.
When visibility is lower than all the limits.
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