LI-COR LI-7820, Instruction Manual

Page: 71 / 92

Setting the span calibration
Follow suitable spanning procedures, as described in Maintenance on page 6-1.
Plumb a span gas to the analyzer air inlet. Use a span gas balanced in air (do not
use a nitrogen-balanced gas).
1
To start a span calibration, enter:
mosquitto_pub -h 172.24.82.42 -t
"licor/niobrara/system/N2O_Span" -m "<N2O tank in ppb>"
l
mosquitto_pub
launches the application to publish (send to the instrument).
l
-h
specifies a host (the Trace Gas Analyzer) followed by the instrument IP
address
l
172.24.82.4x
is the IP address. You can also enter the host name. Both are
given on the instrument display.
l
-t
specifies that you want to subscribe to a topic.
l
"licor/niobrara/system/N2O_Span"
is the topic and hierarchy for the LI-
7820.
l
-m
specifies that you are sending a message from the command line.
l
"<N2O tank in ppb>"
is the N
2
O concentration in PPB.
This initiates the span calibration in the LI-7820. The span is implemented imme-
diately.
2
To check if the span is complete, enter the command:
mosquitto_sub -h 172.24.82.42 -t "licor/niobrara/cfg/N2O_
Span"
The instrument will reply with the span value (near 1) like
"1.00242"
3 Type
Ctrl + C
to stop the script.
Section 7. Communication with the MQTT protocol
7-5 Setting the span calibration