Introduction

During 2005, a set of four special Weatherlink data loggers were introduced. Each of these four new loggers can, in addition to its standard 6510 Weatherlink features, also perform one other specific role, as detailed below. These loggers are jointly referred to as Streaming Loggers by Davis and are available only with an RS232 serial interface, ie not in USB form.

These new loggers fall into two pairs.

The 6540 Weatherlink for APRS and 6550 Weatherlink for Emergency Response look similar to the standard 6510 logger and are able to continuously broadcast a specific fixed-format text string containing the latest weather readings at regular intervals to their serial ports. (This contrasts with the standard logger which generates more complex binary streams of data, but only in response to specific instructions from a linked PC). As a result, the 6540 and 6550 loggers can pass their data to non-PC devices such as a radio transmitter or to PC programs that - unlike Weatherlink - are not specially designed to request and process data from the Weatherlink loggers. Note, however, that while the 6540 and 6550 loggers can continue to store Weatherlink archive data in the usual way for retrieval by the Weatherlink software at a later time while broadcasting their text strings, they cannot simultaneously pass current weather data to the Weatherlink software and to another program or device - it is one function at a time!

The formats of the text strings generated by the 6540 and 6550 loggers are quite distinct from one another and are as required by the published specifications for their respective functions. However, the format for the 6540 APRS logger, in particular, contains several standard fields of current weather readings and so could in principle be useful in feeding data to a program or device quite distinct from its intended APRS application.

The second pair comprises the 6544 Weatherlink for Alarm Output and the 6560 Weatherlink for Irrigation Control. These loggers are distinctive because they have a separate fly lead from the logger module to a block containing a set of external contacts. They still possess the standard RS232 serial connection and can, to the best of our knowledge, be used in all the usual ways when connected to a Weatherlink-compatible program on a PC (except when actually configuring the default operation of these special loggers). In other words and unlike the 6540/6550 loggers above, these 6544 and 6560 loggers can perform their special roles at the same time as passing current and archive data to a program running on the linked PC.

The contact blocks of the 6544 and 6560 are there, not surprisingly, to allow the control of external electrical equipment. The 6560 Irrigation Control unit is very specialised and, as its name implies of course, is intended solely to automatically control irrigation equipment that conforms to a specific interface standard, in response to changing weather conditions.

The 6544 Weatherlink for Alarm Output is perhaps the most interesting and most generally useful amongst these four streaming loggers. It has four pairs of contacts on its contact block and each pair can be individually programmed to open or close in response to some particular weather parameter threshold (or combination of thresholds). See below for further details.

[Pictures of these loggers are not yet to hand - hopefully these can be added at a later date]

6540 Weatherlink for APRS

This logger generates a text string of current weather conditions in the specific APRS format that has been developed to allow amateur radio enthusiasts to broadcast weather readings in an agreed common format. These broadcasts may be collated to allow maps of current weather over an area to be generated automatically. Although the standard Weatherlink software (ie used with a standard 6510 logger) has an APRS function, this works simply by uploading data to a designated central APRS web server and does not directly use wireless broadcast. The 6540 logger, on the other hand, can be connected directly to a TNC modem and thence to a radio transmitter and so allows APRS broadcasts in the full sense.

The fixed text string generated by the 6540 logger is as follows:

• Date/time and location identifiers;
• Wind speed (mph) and direction averaged over 1 minute;
• Maximum gust speed (mph) in last 5 minutes;
• Current temperature (°F)
• Rainfall (0.01") in last hour;
• Rainfall (0.01") in last 24 hours;
• Rainfall (0.01") since midnight;
• Relative humidity (%);
• Barometric pressure (0.1mb);
• Solar Radiation Intensity (W/sqm probably) - special format;

6550 Weatherlink for Emergency Response

This intriguingly named logger generates text strings of current weather readings in a special format needed for input to a program called ALOHA. This (freely-available) program was written for the US Environmental Protection Agency and is intended for the short-term monitoring of spills of hazardous chemicals, whose immediate dispersion pattern will obviously be determined by prevailing weather conditions, especially wind speed and direction.

ALOHA is actually part of a suite of 3 programs called CAMEO, which also include the original CAMEO program (mainly a substantial database of properties of hazardous chemicals, but also a set of tools to log incidents) and MARPLOT, which enables a graphic of the current dispersion pattern predicted by ALOHA to be overlaid on a digital map. MARPLOT was of course originally intended for use in the US where highly-detailed digital maps in a compatible format are freely available. With a little work, maps in a wide variety of formats (including bitmaps) can be made to work perfectly adequately in MARPLOT so the program can be used acceptably in any part of the world, but of course some cost may be involved in sourcing the maps outside of the US.

The 6550 unit clearly opens the way for use with the fascinating CAMEO software, but prospective users should note: (i) that the software is only intended for use immediately after an incident (up to 1 hour after the event and 10km distance from the spill  site - simply because changing weather, the unknown topography of the spill area etc would make further dispersion predictions unreliable at longer times and greater distances); and (ii) some familiarisation with the CAMEO software, how to source and import maps into MARPLOT, etc is needed.

As a result, the 6550 logger is not likely to have much public appeal for UK users. But if any professional users might be interested in learning more about this logger and its associated software then we can help and advise further.

For the record, the text string generated by the 6550 logger is as follows:

• Station ID;
• Mean wind speed over 5 minutes (m/sec);
• Mean wind direction;
• Standard deviation of the wind direction;
• Mean air temperature (°C) over 5 minutes;
• Current wind speed (m/sec);
• Current wind direction;
• Current air temperature (°C);
• Battery status;

6544 Weatherlink for Alarm Output

This is probably the most generally applicable unit amongst the four special streaming loggers. As noted above, this 6544 logger is able to control external electrical equipment via a contact block that contains four sets of contacts and that can open or close in response to the triggering of numeric thresholds of weather parameter values. These contacts are essentially like solid-state relays, which are limited to low voltage (28V AC / 48V DC) use but can switch respectable currents (1A or greater). These contacts could obviously be used indirectly to control AC mains equipment, but an intermediate mains-rated relay (or similar solid-state device) and power circuit would be needed.

This logger unit fills a need we're often asked about in relation to Vantage Pro stations, namely is there a way of turning some external equipment on or off in response to changing weather conditions? Well the answer now is very definitely: yes!

 The 6544 logger also complements the Weatherlink Email add-on module, which is used specifically for messaging (eg by email or SMS) about current weather conditions, whereas the 6544 logger is able to initiate some physical action as a result of changing weather conditions. Indeed there's no reason why the 6544 logger and the Email Module could not both be used on the same installation to carry out their distinct functions, ie the 6544 to control external equipment and the Email software Add-on Module to relay status messages by email and/or SMS to operators.

The parameter monitoring available on the 6544 is very comprehensive. Any parameter measured by the VP installation, including any supplementary sensors fitted and also derived parameters such as dew point can be monitored. Trigger points can be set to: greater than, less than, or equal to a specified level. Other function such as between two specified values (or not between) and even a trend value can be used. Multiple combinations can also be set, when a contact closure can be triggered is any condition in a set is reached or only if all conditions in the combination are met. And a completely different combination of weather conditions can be set for each of the four pairs of contacts.

The 6544 logger is programmed as follows: A special Streaming Logger utility, which is installed automatically along with recent versions of Weatherlink, is run on the linked PC. (NB Normal Weatherlink software operation must be stopped whilst this utility is running). The utility contains a comprehensive set of screens that allow all the features listed above to be specified and downloaded to the logger. Once programming of the 6544 unit is complete, the Streaming Logger utility is closed and normal Weatherlink software operation can be resumed.

6560 Weatherlink for Irrigation Control

This logger can control compatible irrigation equipment apparently at the same time that it is performing routine data logging. Compatible equipment would be either industrial units that expect pulsed inputs of wind, rain and ET in a standard protocol and available from the contacts in the 6560 connector block or residential units based on an ET output but with other constraints that can be entered in the control program.

Clearly, this logger is not going to be of general interest, but for those subsets of professional users who are familiar with the control and use of irrigation equipment, this logger may be a cost-effective solution to their needs.