Omega Engineering OMB-CHARTSCAN 1400, User Manual

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Registers, Data Formats, & Queries Appendix C
C-2 ChartScan User’s Manual
Using High/Low/Last (HLL) Registers
The High/Low/Last (HLL) registers are an alternative method of getting channel data from the ChartScan unit.
The HLL registers are updated during an acquisition at the current programmed scan rate. At any time, the HLL
registers can be queried for channel values without affecting the buffered data.
The returned data is in the engineering unit and format (ASCII or binary) defined by the user. Data formats are
described later in this appendix.
HLL Register Contents
The HLL Registers contain the following for each configured channel:
• The High Reading for the channel since the beginning of the current acquisition or since the last HLL query
(
U5
).
•
The Time/Date Stamp of the High Reading.
• The Low Reading for the channel since the beginning of the current acquisition or since the last HLL query
(
U5
).
• The Time/Date Stamp for the Low Reading.
•
The Last or most recent Reading for the channel.
Note: HLL Registers will only be updated for configured channels. Furthermore, you can only access HLL
Registers for configured channels. You can not access HLL Registers of non-configured channels.
You can clear the High and Low readings for each actively configured channel in any of the following ways:
•
Power cycle ChartScan.
•
Create a new channel configuration.
•
Explicitly clear the readings by command. This is discussed in the next section.
Note: When the High and Low values are cleared, their associated Time/Date Stamps are cleared as well.
After being cleared, the new High and Low values (along with their associated Time/Date Stamp) will
be initialized on the next updating of the HLL Registers.
Accessing HLL Registers
You can access the HLL Registers by issuing commands from the controller. You can use the commands to
access any or all the HLL contents of configured channels, as well as clear the High and Low readings and
associated Time/Date Stamps. Briefly, the commands are as follows:
U4
Read HLL Registers for all configured channels.
U5
Read HLL Registers for all configured channels and reset the High and Low values.
U13
Read Last only for all configured channels.
R#
Read Last only for channel(s) specified.
Note: The HLL registers contain the highest and lowest values of the channel since it was last cleared and the
last value read, for each channel in the channel scan.
Two queries are available to read the HLL registers:
U4
and
U5
. The
U4
command requests the HLL data,
while
U5
requests the HLL data then clears and resets the high and low value to the last value . If not cleared,
the high and low will be maintained.
All HLL data will be sent to the controller in the order dictated by the scan configuration, and in the format
specified by the Data Format command (
F
). The HLL data is retrieved in the following sequence:
•
high - the high reading
•
ht - the high time/date stamp
• low - the low reading)
•
lt - the low time stamp
•
last - the last reading