Campbell Scientific LoggerNet Datalogger Support Software - Manual (Page 110)

Section 4. Setting up Datalogger Networks
If data collection is enabled for input location data (Inlocs) on the
CR10X-TD/PB family dataloggers or Public tables on CR1000, CR3000,
CR800, CR5000 or CR9000 dataloggers, the current values will be collected
every time a scheduled collection occurs, whether or not the values have been
updated. Therefore if your scan interval were one minute in the datalogger
program, and the data collection interval were 30 seconds, you would get two
identical records in the Public table for each one minute scan.
4.2.5.2.3 Communications Path Considerations
When setting up data collection intervals for the dataloggers you should
consider the communications path to the datalogger, and its affect on how often
you can retrieve data.
Phone modems require anywhere from 10 – 30 seconds or more to establish
communication, negotiate baud rate, and start transferring data. Therefore, it is
not a good idea to schedule collection by phone modem more often than once
every two minutes. The time to make a call and start communications should
be considered when you are collecting from multiple stations by phone.
Sufficient time should be allowed for the server to dial the station, retrieve the
data, and then contact the next station. There should be enough time between
calls to the first station that the calls to the other stations using the same
modem can be completed. Otherwise the collection schedule will be delayed
waiting for the previous stations to finish.
RF networks with repeaters also add time delays since each modem must be
contacted and then pass the message on to the next RF modem and so on. Each
of these operations takes time so the time schedule for RF networks with
repeaters should allow enough time for the link to be established with the
datalogger and collect the data.
Consideration should also be given to other operations such as clock sets,
program downloads, or manual data requests to the datalogger. These require
significantly more time and can affect RF network responsiveness.
Any network setup using a phone to RF should be reviewed for collection
scheduling issues due to the combinations of time delays associated with RF
data collection.
4.2.5.3 Setting Up Scheduled Data Collection
The data to be collected and the output file locations and format are specified
on the datalogger’s Data File or Final Storage tab. The Schedule tab is used to
define the interval on which the LoggerNet server will check the datalogger for
new data. If new data exists, it will be stored in the data files and the
LoggerNet data cache.
To set up a data collection schedule for a datalogger, first ensure that your
device map has been configured with all of the devices listed as they actually
exist. Next, determine which tables or final storage areas should be collected
from the datalogger each time a data collection attempt is made. If no tables
are selected on the Data Files tab or the Final Storage Area is not enabled for
collection, no data will be collected from the datalogger.
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