IOtech MultiScan 1200, User Manual

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TempScan / MultiScan User's Manual Chapter 12: System Configuration 173
Scan Configuration
Configuring the Scan
Channel Scan & Scan Interval Definitions
Although a fully-expanded TempScan/1100 or MultiScan/1200 system of 31 available scanning-card
slots can provide a maximum capacity of 992 or 744 channels, respectively, only those channels
configured in the channel scan are collected and available to the controlling computer. Channels are
always scanned in ascending order, regardless of the sequence you input. The same configuration is
used in reading channel data through the High/Low/Last Registers or the Acquisition Buffer.
Scan configuration is also accomplished using the Configure Channels (
C
) command. This command
allows up to a maximum of 992 TempScan/1100 channels or 744 MultiScan/1200 channels to be
assigned as individual channels or as a range of channels. The maximum number of channels can be
configured in any sequence, but these channels will be ordered sequentially for the scan.
Note:
TempScan/1100 or MultiScan/1200 scans cannot randomly access the selected channels.
Configuring the Scan Interval
The scan interval is the time lapse between successive scans (or the inverse of the scan frequency).
Using the
Set Scan Interval (
I
) command, you can program the scan interval with any duration from a
99-hour period down to as fast as the unit can run under the current channel configuration.
The TempScan/1100 or MultiScan/1200 has two distinct types of scan intervals:
•
Normal Scan Interval. The normal scan interval is used when the TempScan/1100 or
MultiScan/1200 unit is acquiring scans before the Trigger (trigger start event) has occurred, or
after the Stop (trigger stop event) has occurred. These two scanning regions are called the Pre-
Trigger scan and the Post-Stop scan, respectively.
•
Acquisition Scan Interval. The acquisition scan interval is used when the TempScan/1100 or
MultiScan/1200 unit is acquiring scans after the Trigger (trigger start event) has occurred, but
before the Stop (trigger stop event) has occurred. This middle scanning region is called the Post-
Trigger scan.
The Set Scan Interval (
I
) command is used to set these two types of scan intervals. For example, the
following command –
I00:00:10.0,00:00:00.1
– will set the normal scan interval to once every
10 seconds and set the acquisition scan interval to once every 0.1 seconds. One useful application for
having two different scan intervals is when events after the Trigger require faster sampling than those
before the Trigger , such as during alarm conditions.