Page B-2
LiQuilaz II E and S Operations Manual
Appendix B RS-485 Communication Protocol
Sample Initialization
The following command sequence is typical when starting the instrument:
CSI CSIZE CSS
This sequence does the following:
• Sets the desired sample interval
• Sets the channel size values
• Starts the LiQuilaz II sampling
Data Processing
The LiQuilaz II can be polled for data in the following two ways:
Slow protocol
which is how all the regular commands are transmitted.
Fast protocol
where the term “Fast” refers to the ability to get data as a sample is created, not just
at the end of a completed sample. It should be noted that a combination of “Slow”
and “Fast” data polling is allowed.
Slow Polling
The following sequence is typical for a “Slow” data poll:
Once the LiQuilaz II has started sampling the user must poll the instrument to check
its data queue. This is done by transmitting the
CQC
command. The instrument
responds with a RQC and two values.
• If the first value is -1, the instrument is not sampling and needs to be re-initialized
and started as outlined in the Instrument Initialization on page
B-2 sections.
• If the instrument responds with a value of
0
, there is no data at this time; send
another
CQC
command.
• If the instrument responds with a value of
1
or greater, data is present.
To receive the stored data, the user now must transmit the
CTD
command.
If the data is received with no problems, the user should issue the
CPQ
command to
“pop” the data off of the LiQuilaz II data queue.
If the data is not received correctly, the
CTD
command can be reissued.
This procedure can be repeated until the user no longer wishes to receive sample data.
The second value reported by the sensor with the RQC response represents its
sampling status (1=Sampling).
NOTE:
The CQC command is typically transmitted to the instrument at twice the
sample interval.
