How the System Works

The weather system has two parts: a solar-powered base station and the Harvest database with its web server. In the field, the base station station records weather data (temperature, wind, rainfall, etc). Every hour during normal conditions or every minute under frost conditions, the system sends its new data via a GSM/GPRS/3G cellular link to the central Harvest database. Our database processes, records, backs up and then publishes your weather data online.

On the website you can view current graphs as well all your weather history, and you can configure your alarms and password.

Temperature

Temperature is measured using digital Dallas one-wire sensors with a range of -55°C to +125° and an accuracy of 0.5%. Sensors are calibrated at Harvest to 0.1% at 0°C in an environmental chamber with a calibrated 0.01% platinum temperature sensor.

Rainfall

Rainfall is measured with a tipping-bucket rain gauge. Older systems were supplied with the Pronamic gauge (1mm per tip) while all current systems use the higher accuracy Davis 7852 gauge (0.2mm per tip).

Wind Speed/Direction

Wind is measured using a Davis 7911 anemometer or Novalynx 200-WS-02, usually mounted directly on top of the weather station. The Davis is rated from 4–280km/h and has an accuracy of 5%. The Novalynx is rated from 0–160km/h, has an accuracy of 3% and is made out of more durable metal components.

Humidity

Humidity is measured using a Honeywell HIH-3610 sensor, which has a range of 0–90% and an accuracy of 5%. After the humidity data has been temperature-compensated, the dewpoint and wet bulb temperatures are calculated from the humidity and the air temperature.

Soil Moisture

Soil Moisture is measured using either a Decagon EC-5 or 10HS probe. The newer Decagon 10HS sensor has an accuracy of ±3% across all soil types. More info on both sensors can be found on the Decagon website.

Other Sensors

Other sensors are available, such as leaf wetness, soil temperature, solar radiation, barometric pressure, flow meters, float switches and pressure sensors. Other sensors can be interfaced to via spare analog and digital inputs.

Alarms

Every system is configured by default with a frost alarm but can include other alarms too, eg. heat, wind machine on/off, pump pressure low, etc. If frost alarms are turned on and the temperature goes below the set frost alarm temperature, a text message, voice message or email is sent to the specified user(s). The frost alarm temperature threshholds and alarm roster can be modified online.

Each sensor can have both a frost alarm and a heat alarm, and each alarm is specified with two alarm levels and a reset level. For a frost alarm, a paging message is sent when the temperature crosses below each of the two alarm levels. No more alarms are sent until the temperature has crossed back above the reset level, at which time the system goes back into "wait for alarms" state. Heat alarms work the same way, but the temperature must cross above the given temperatures for an alarm, and back below the reset level to reset.