Note: This issue applies in the main only to the USB version of the Weatherlink data logger (6510USB), although it can occasionally also be encountered with serial port WL loggers connected to a PC’s USB port via an external serial-to-USB adapter.

Symptom: The classic symptom here is that the logging system will perform perfectly well for a period, eg just 30 minutes in bad cases, but typically ranging up to many hours or days, but then communications with the WL logger will be lost. Data will then no longer be available to the linked PC, although the console should continue to work as normal. The exact symptoms can vary in severity but in the worst cases a PC crash can be the end result.

Background: This USB dropout issue has been reported in various online weather forums in the past but in reality now affects only a small percentage of users. It tends only to be seen when the the PC is continuously connected to the USB logger and is being used to pass a constant stream of real-time data to the PC. If you only connect a PC to the logger at intervals of every few hours or daily or less often, it’s unlikely that you will ever see this problem. Even if you do require a real-time data stream then only an unlucky small minority will ever encounter USB port dropout.

Every time that the Weatherlink (or other) software requests data from the WL logger, a request is passed to the relevant USB port to pass on to the logger. But if the PC’s USB port becomes unresponsive (which is what happens during USB dropout) then the request cannot be sent from PC to logger and hence the software flags up a communications breakdown with the logger. Once this happens then the unresponsive port state tends to persist until the port is reset, for example by unplugging the USB cable from the logger and reconnecting it – his action is usually enough in itself to cause the PC’s USB driver to reload and hence to reactivate the USB port. Of course, the whole idea of a constant, automated stream of weather data is that it doesn’t require manual intervention to operate continuously, 24/7, but if manual unplugging and replugging of the USB connection is enough to restore communications with the logger then that is a good diagnostic sign that the problem you’re encountering is indeed one of USB port dropout.

USB dropout tends to have one of two causes:

  • The USB port has been deliberately powered down by the PC as part of its power-saving procedures;
  • The port has become unresponsive because of interference;

The first of these possibilities – a power-saving issue – is uncommon but it should always be ruled out. Double-check that nowhere in the PC’s power-saving settings are the USB ports set to be automatically powered down at any stage. Sometimes, checking this may require delving quite deeply into the power-saving settings.

However, power-saving is not usually the culprit and interference-related causes are much more likely. See the USB Interference topic for further discussion.

Last modified: Mar 13, 2015


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