下降警報
下降報警由以下參數(shù)的下降水平引起：
測量值超過預先配置的閾值，還將導致：相關報警LED點亮。n、 鎖存報警器
鎖定報警是一種即使在監(jiān)測的液位不再超過報警閾值。警報LED將保持點亮，直到操作報警復位。
o、 非鎖存報警非鎖定報警是指僅在被監(jiān)控的液位超過報警閾值。報警指示燈報警級別保持時，將保持點亮，但將自動點亮當監(jiān)測的液位不再超過報警閾值時復位。
p、 正常通電斷電時，正常通電繼電器激活例如，在系統(tǒng)電源故障的情況下）。LED將發(fā)生報警或故障時點亮，無論繼電器處于配置狀態(tài)。
q、 正常斷電通電時，正常斷電繼電器激活（例如，在報警條件下）。LED將點亮
發(fā)生報警或故障時，無論繼電器如何配置狀態(tài)。
r、 延時報警（僅限2Vx軟件版本）
響應某些繼電器的報警事件的操作可能是：通過對繼電器應用延遲功能進行修改。時滯函數(shù)
可在以下情況下將繼電器的激活延遲一段時間：發(fā)生報警事件和/或在一段時間內(nèi)保持繼電器激活
報警事件清除后。延時設施可用僅用于高完整性中繼卡的中繼RL2至RL8。
延時功能有助于防止虛假報警，并確保外部電氣設備的適當最小運行時間
連接到繼電器的裝置?？刂瓶ò姹?/p>
自System 57最初推出以來，有幾個新功能：已添加以增強5701控制卡的功能。
每個軟件版本的關鍵功能如中所示下表。請注意，安裝在現(xiàn)有卡上的軟件不能：
升級，但所有版本的軟件和硬件都已完全升級
向后兼容，因此新卡可以合并到現(xiàn)有卡中毫無困難的系統(tǒng)
Falling Alarm
A falling alarm is caused by a falling level of the parameter being
measured crossing a preconfigured threshold and will also cause
the associated alarm LED to illuminate.
n. Latched Alarm
A latched alarm is an alarm that will remain active even though the
level monitored no longer crosses the alarm threshold. The alarm
LED will remain lit until the alarm reset is operated.
o. Non-latched Alarm
A non-latched alarm is an alarm that only remains active while the
level being monitored crosses the alarm threshold. The alarm LED
will remain lit while the alarm level remains but will automatically be
reset when the level monitored no longer crosses the alarm threshold.
p. Normally Energised
A normally energised relay is activated when the power is removed
from it, (eg. in the event of a system power failure). The LEDs will
illuminate when an alarm or fault condition occurs irrespective of the
relay configured state.
q. Normally De-energised
A normally de-energised relay is activated when the power is applied
to it, (eg. in the event of an alarm condition). The LEDs will illuminate
when an alarm or fault condition occurs irrespective of the relay
configured state.
r. Time Delay Alarms (Version 2Vx Software only)
The operation in response to alarm events of certain relays may be
modified by applying a delay function to the relays. Time delay functions
are available to delay the activation of a relay for a short period after
an alarm event occurs and/or to maintain relay activation for a period
after the alarm event has cleared. The time delay facilities are available
for relays RL2 to RL8 of the High Integrity Relay Card only.
The time delay function is useful to prevent spurious alarms and to
ensure appropriate minimum operating times for external electrical
apparatus connected to the relay.Control Card Versions
Since the original launch of System 57 several new features have
been added to enhance the capabilities of the 5701 Control Card.
The key features for each software version are illustrated in the
following table. Note that the software fitted to existing cards cannot
be upgraded, however all versions of software and hardware are fully
backward compatible so new cards can be incorporated into existing
systems without difficulty
