Relay Controls; Table 7 Control Logic Of Relay Controls 1 And 2 - Vaisala PWD22/52 User Manual

USER'S GUIDE____________________________________________________________________
40 __________________________________________________________________ M210543EN-E

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 relay control of PWD22/52 can all 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 set 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 (5) 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
States of Relay 1 and 2
1 OFF 2 OFF
1 ON 2 OFF
1 ON 2 ON
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.