Symptom: Real-time data is passing successfully from logger to computer, but attempts to download archive data are failing, either partially or completely.
Background: Davis loggers can all generate two quite distinct types of data: real-time data (sometimes called Loop data) and archive data. Real-time data is passed to the computer about every 2-3 seconds and is the data source for the Bulletin mode of the Weatherlink software, ie the real-time display that shows, for example, live wind data. Archive data is the summary data which the logger generates at preset intervals (typically every 5 to 30 minutes according to the user settings) and which accumulates within the logger until a computer is connected and an archive download is requested.
Archive download issues are seen most often with the Weatherlink software, for the simple reason that most third-party programs use only the real-time data as their primary data feed, although some do also have a ‘catch-up’ mode which makes use of archive data. (Using only real-time data means of course that the connected computer must be switched on 24/7 if data is not to be lost, which is a significant drawback for many users and is one one the main reasons why the Weatherlink program remains so popular.)
This topic covers only errors seen with archive downloads. It assumes that real-time data is being passed successfully to the computer; if this is not the case then go back and review the general Weatherlink logger topic,. The troubleshooting notes below assume that you know what the terms ‘archive database’ and ‘Browse mode’ mean in the context of the Weatherlink program. If not then please refresh your memory from the Help within the Weatherlink software.
Types of archive download error:
There are, broadly, three main types of error that can be encountered with archive downloads:
- ‘No new data to download’: Attempts to download archive data always give this same error message;
- Incomplete or repetitive downloads: Downloads start OK but do not complete successfully. Sometimes the program will repeatedly report that it’s downloading the same (or similar) large number of records, but new data never appears in the archive database;
- Errors in downloaded data: Downloads do complete successfully, but problems with the downloaded data subsequently become apparent. For example: attempts to use the Plot module cause the Weatherlink program to crash; or whole blocks of data in the newly-downloaded records appear to be missing when viewed in Browse mode, typically the date/time values may be present but the rest of the record is not showing. (NB Note the reference to whole lines or blocks of data being missing. If only data that depends on one sensor such as the temperature sensor is missing then this is almost certainly a sensor fault and not a download issue.);
For all of these types of error, troubleshooting should proceed along the same course: First, check that there is not some simple and easily-remedied cause; Second, if there’s still a problem then more in-depth troubleshooting is needed. Please see the Simple causes and Detailed troubleshooting subtopics, respectively.