Obvius A7801 - Manual (Page 20)

verify if your firewall will allow NTP packets to pass through. Generally, it is better to use a local time server if possible.
The time server time.obvius.com supports both NTP and Rdate time protocols.
Note: the AcquiLite only supports the NTP time protocol.
Universal Time Is Your Friend
Log data is stored in UTC time. This allows data collection services such as BMO to collect data from multiple sites in
different time zones. If you are operating your own database system to store log data from the AcquiLite, it is best to store
the data in UTC time in the database as well, and only convert it to local time when generating the final report or graph for
the user.
If you store data in Local time, you will have the following issues.
1) Local time is relative. Is Local the time where the AcquiLite exists, or Local to where the data is stored. If local to the
AcquiLite, you must shift each AcquiLite data set depending on its location.
2) There are about 11 time zones in the US. Some observe DST, others do not. These include Alaska, Aleutian, Arizona,
Central, Eastern, Hawaii, Indiana, Michigan, Mountain, Pacific, and Samoa.
3) When converting to local time, there will be one hour of overlapping data in the fall when the time is adjusted for
Daylight Savings time. ie, log entries run 12:45, 1:00, 1:15, 1:30, 1:45, 1:00, 1:15, 1:30, 1:45, 2:00am. This will prevent
you from sorting your data by time in your database.
4) In the spring, you will have a gap in the data from 1:59 to 3:00am. This can cause problems if you are calculating
demand values based on consumption.
5) Converting Local time to any other timezone usually involves converting it to UTC first.
Using UTC time solves these problems elegantly. The best practice is to store data in the database in UTC format and then
convert the information when generating a report for the user.
For example, if you wish to draw a graph of KW over Time, prompt the user for a date range, say Jan 1 midnight to Jan 2
midnight. Take the user specified end points and convert these times from Local time to UTC. Next, create an SQL query
using the new UTC formatted data as your select statement. ie:
SELECT * from TABLE where time > '2003-01-01 08:00:00' and time < '2003-01-02 08:00:00'
Note the time is 8 hours ahead of local time. This example is for Pacific which is 8 hours off from UTC. This will return a
list of data points between the two specified time ranges. Next, plot the data on a graph, using the UTC times for start and
end points. Lastly, when drawing the 'time' legend on the graph, convert the values back to Local time before displaying. Ie,
2003-01-01 00:00:00 to 2003-01-02 00:00:00. Any division lines on the time axis can be handled the same way. The
advantage of using this technique is that it will properly draw a graph across DST change boundaries. The graph axis is
based on UTC time with no DST, and will not show a gap or overlap a the time of the change. The axis labeling will be
correct as well, matching the UTC times precisely.
Another way to handle the conversion is to query and convert all the returned timestamps to local time before drawing the
graph. This is useful if you do not have detailed control over the graph legend drawing process. This technique will not
properly graph across DST changes as the graph is based on local time including DST changes.
System logs
The AcquiLite can keep several log files that report the general operation of the system, not related to the normal data logs.
These include the following:
● System Messages: A list of system log messages related to the operation of the AcquiLite. These include the upload log
messages, dialin/out, time changes, and any system errors that have ocurred.
● Logger Configuration File: This page allows you to view, in text format, the configuration options of the system.
● Pulse input configuration file: This page allows you to view, in text format, the configuration options of the pulse inputs.
● Pulse log data (html): This page will allow you to view, in a web page, all the stored pulse log data on the AcquiLite.
● Pulse log data mb-001.log (export) This page will provide the pulse log data in text (csv) format. You may need to
right-click on the mb-001.log link and select “save target as” from the menu to save the log data to your computer hard
disk.
Purge Log Files: This button will clear all the system log files listed on this page, but not the meter data log files. (deletes
kernel, boot, ftp, messages, upload log files)
Page 20 A7801 AcquiLite – Data Acquisition Server