Dynalco SC-2124M Scanner/Monitor - Manual (Page 18)

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4.3 ALARM
The SCANNER provides a precautionary ALARM warning to alert the user to potentially
hazardous or dangerous input conditions. The SCANNER monitors all enabled scanner
channels’ current analog input readings and compares each channel’s reading with a user-
configurable ALARM threshold. If any channel’s ALARM threshold is exceeded, the
SCANNER TRIPs an ALARM condition and blinks the ALARM indicator LED on the front
panel. A SCANNER ALARM is not latched and clears if no channel’s ALARM threshold is
faulted.
4.4 SHUTDOWN
The SCANNER provides a protective SHUTDOWN fault to guard against hazardous or
dangerous fault conditions. The SCANNER monitors all enabled scanner channels’ current
analog input readings and compares each channel’s reading with a user-configurable
SHUTDOWN threshold. If any channel’s SHUTDOWN threshold is exceeded, the
SCANNER TRIPs a SHUTDOWN condition and blinks the SHUTDOWN indicator LED on
the front panel.
When a SHUTDOWN occurs, the SCANNER saves the channel that caused the
SHUTDOWN to non-volatile memory as the First-Out channel. This First-Out channel is the
first channel that the SCANNER detects in a SHUTDOWN fault state. The SCANNER
displays the First-Out cause of the SHUTDOWN on the Main SCANNER Screen (See
Section 5.2.3). A SCANNER SHUTDOWN is latched and is not cancelled until
acknowledged by a RESET (See Section 4.1).
At the time of a SHUTDOWN, other scanner channels may be in a SHUTDOWN fault state.
Since several channels may be faulted, it is possible that another scanner channel besides
the First-Out channel caused the actual SHUTDOWN—the SCANNER merely detected and
labeled one faulted channel before the actual First-Out channel.
To aid the user in analyzing a SCANNER SHUTDOWN, the SCANNER also takes a Snap
Shot of all enabled scanner channels’ analog input readings at the time of the SHUTDOWN
and saves these Snap Shots to non-volatile memory. These Snap Shot values are displayed
on the SNAP Screen (See Section 5.2.7) and may be viewed after the user acknowledges
the SHUTDOWN condition via a SCANNER RESET. Only one set of SHUTDOWN Snap
Shot values is saved to memory at any one time. When a subsequent SHUTDOWN occurs,
the new Snap Shot values overwrite the old values in memory.