Advantech Data Acquisition Modules ADAM 4000 - Manual (Page 50)

Chapter
3
Chapter 3 I/O Modules 3-23
Every A/D conversion will be followed by a comparison with the
High and Low limits. 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 limits. An alarm in Latching mode can 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 to within 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 the host computer involvement.