Using Automatic Scan List Sequencing (List-of-Lists)
It is not unusual in data acquisition that you will want to scan groups of
channels at different rates. Some of your system’s channels may measure
fast changing signals that need to monitored at high rates while other
channels measure slowly changing signals that can be scanned less often.
The HP E1313/E1413 provides an easy way to scan groups of channels at
up to four different rates. The module not only has four scan lists (
LIST1
through
LIST4
) in which you define lists of channels, it also has
LISTL
which you define as a list of scan lists (therefore the term List-of-Lists).
When
LISTL
is selected as the current “ scan list” , a trigger will cause the
module to execute each scan list defined in
LISTL
in the order it was
defined. The overall procedure is:
1. Define each scan list to be executed using the command
ROUTe:SEQuence:DEFine LIST
n
(@<
ch_list
>
).
2. Define
LISTL
with the sequence of scan lists to execute using the
command
ROUTe:SEQuence:DEFine LISTL (@<
ch_list
>
).
3. Set
LISTL
as the current scan list using the command
ROUTe:SCAN LISTL
.
4. Set up the trigger system for continuous mode or counted mode
(see previous section).
5. Trigger the module to start scanning.
A Simple Example
What controls the relative rates that the channel groups are scanned is the
frequency that individual channels appear in each scan list and the frequency
that these scan lists appear in
LISTL
. As a very simple example let’s say you
want to scan channels 0 through 3 four times as often as channels 4 through 7.
Since there are two groups we will use two scan lists. The scan list to be
executed least often contains the channels from both the high rate group and the
low rate group [
ROUTe:SEQuence:DEFine LIST1, (@100:107)
]. The scan list
to be executed most often contains only the channels from the high rate group
[
ROUTe:SEQuence:DEFine LIST2, (@100:103)
]. Now we will define
LISTL
to
scan the high rate group four times for every scan of the low rate group. Define
LISTL
to reference scan list 2 three times and scan list 1 once
[
ROUTe:SEQuence:DEFine LISTL,(@2,2,2,1)
]. When triggered, the module
will scan these channels:
120 Understanding the HP E1313/E1413
Chapter 4
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