Section 7. Communication with the MQTT protocol
Topic
Description
Hierarchy
1
Data
licor/niobrara/output/concentration
2
Header for the data file
licor/niobrara/output/concentration/units
3
Diagnostic information for
data
licor/niobrara/output/diagnostics
4
Header for diagnostic
information
licor/niobrara/output/diagnostics/units
5
Set and read the calibration
baseline (0)
licor/niobrara/cfg/Start_Peak_Base_Line_Cal
6
Set N
2
O span calibration
licor/niobrara/system/N2O_Span
7
Read the N
2
O span
calibration
licor/niobrara/cfg/N2O_Span
Table 7-1
. Topics and hierarchy in the LI-7820.
Basic commands in a terminal program
The instrument can be controlled from a terminal program (macOS) or command
prompt program (Windows). With trace gas analyzers, that means you can set the
zero and span calibrations, read the calibrations, and read data with diagnostics. In
the following section, we describe how to perform these basic functions.
This tutorial uses Eclipse Mosquitto, an open source message broker from the
Eclipse Foundation which can be downloaded from mosquitto.org/download/.
Install it on your computer. We will use two components of mosquitto for this
tutorial:
mosquitto_pub
, which "publishes" information to the instrument (as in,
sets the span calibration); and
mosquitto_sub
, which "subscribes" to information
from the instrument, such as current calibration parameters, and measurements.
7-2
LI-7820 N₂O/H₂O Gas Analyzer
Summary of Contents for LI-7820
Page 1: ...LI 7820 N2O H2O Trace Gas Analyzer Instruction Manual ...
Page 2: ......
Page 10: ...viii ...
Page 28: ...Section 2 Getting started 2 12 LI 7820 N O H O Gas Analyzer ...
Page 36: ...Section 3 Applications of the LI 7820 3 8 LI 7820 N O H O Gas Analyzer ...
Page 52: ...Section 4 Software overview 4 16 LI 7820 N O H O Gas Analyzer ...
Page 66: ...Section 6 Maintenance 6 8 LI 7820 N O H O Gas Analyzer ...
Page 84: ...Appendix B Additional safety information B 6 LI 7820 N O H O Gas Analyzer ...
Page 91: ......