Chapter 4_________________________________________________________________ Installation
VAISALA ________________________________________________________________________ 51
- 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 13
Control Logic of Relay Controls 1 and 2
States of Relay 1
and 2
Corresponding Visibility Conditions
1 OFF 2 OFF
When visibility is higher than LIMIT 1 and LIMIT 2.
1 ON 2 OFF
When visibility is lower than LIMIT 1 but higher than
LIMIT 2.
1 ON 2 ON
When visibility is lower than LIMIT 1 and LIMIT 2.
Below is a table of a control logic example of relay controls 1 and 2
and 3 when all the relay controls are driven by visibility limits.
Table 14
Control Logic of Relay Control 1, 2, and 3
Relay States
Corresponding Visibility Conditions
1 OFF 2 OFF 3 OFF
When visibility is higher than all the limits.
1 ON 2 OFF 3 OFF
When visibility is lower than LIMIT 1 but higher
than LIMIT 2 and LIMIT 3.
1 ON 2 ON 3 OFF
When visibility is lower than LIMIT 1 and LIMIT 2
but higher than LIMIT 3.
1 ON 2 ON 3 ON
When visibility is lower than all the limits.
When the third relay control output is set to be driven by the hardware
status, it pulls whenever a hardware alarm is detected For details, see
section System Configuration Commands on page 70.
