Advantech Data Acquisition Modules ADAM 4000 - Manual (Page 38)

Chapter
3
Chapter 3 I/O Modules 3-11
Alarm signaling
Analog input modules include High and Low alarm functions. High
and Low alarm limits may be downloaded into the module’s EEPROM
by the host computer.
The alarm functions can be enabled or disabled remotely. When the
alarm function is enabled, both Digital Output channels are used to
indicate the High and Low alarm states. Digital Output channel 1 (DO1)
equals to High alarm state, and Digital Output channel 0 (DO0) equals
to Low alarm state. The High and Low alarm states can be read at any
time by the host computer.
Every A/D conversion will be followed by a comparison with the
High and Low limit. When the input value exceeds one of these limits,
the High or Low alarm state is set to ON.
There are two alarm mode options, Momentary and Latching.
If the alarm is in Latching mode, the alarm will stay on even when
the input value returns within the limits. It can also be turned OFF by
issuing a Clear Alarm command from the host computer. A Latching
alarm is cleared by the module when the opposite alarm is set.
When the module receives a value that is lower than the Low alarm
limit, it will clear the High alarm and turn the Low alarm ON.
When the alarm is in Momentary mode, the alarm will be turned OFF
as soon as the input value returns within the limits.
The arrangement of coupling High and Low alarm states with
Digital Output lines may be utilized to build ON/OFF controllers that
can operate without involving the host computer.