Soil sensor minimises environmental damage

Murata has initiated projects using the soil sensor with partners all over the world. One example is a collaboration with Vietnam’s Can Tho University which began in 2017. The university has a deep knowledge of agricultural and environmental research in the Mekong Delta, and the project included conducting field trials of a soil monitoring system to observe the condition of agricultural land in the delta.

Vietnam’s Mekong Delta region is subject to the salinity impact from the infiltration of seawater during the dry season as a result of a decline in the volumetric flow rate of the Mekong River, and the action of the tides under the impact of climate change driven by global warming. In addition to salt damage, the environment for agriculture has become harsher due to the increasing severity of droughts and floods.

Murata developed a compact 13cm sensor that draws on the company’s know-how and expertise in the fields of electronic components, circuit design and software design to measure the condition of agricultural land, and to channel water with high precision. Combining these observations with independently developed monitoring tools it is possible to visualise and analyse the environmental conditions with a view to making improvements.

In this way the sensor contributes to the implementation of IT in agriculture in the Mekong Delta region by preventing salt damage to rice paddies and orchards, ameliorating salt and sulfur contamination of agricultural land and water channels, and creating a mechanism to comprehensively manage fertilisers, crops and irrigation systems.

The sensor is able to monitor two types of electrical conductivity (EC), temperature and the moisture content of the soil. Being able to accurately diagnose EC levels enables growers to realise ideal fertiliser timing, and of course the water content of the soil similarly enables accurate and timely watering. By being able to use water intelligently, this valuable resource is not wasted, thus helping the environment.

Able to operate from a three to 6.5V, 50mA (maximum) supply, the sensor’s EC measurement range is zero to 5.0dS/m with an accuracy of ±3% full scale. Its moisture measurement range is 0 to 60%VWC at an accuracy of ±3% full scale, and its temperature range is -20 to +70°C with an accuracy of ±1°C.

Protected to IP68 dust and water resistance including reliable rust proofing for use in harsh environments, this high performing, highly accurate sensor is more rugged than competing sensors of its type and accordingly is positioned at the high end of its genre. The sensor’s interface capability embraces UART, RS232E, RS485 and SDI-12, and maximum cable length is specified as 3m@UART, 10m@RS232E and 300m@RS485.

In the project, the wireless transmitter-receiver system used consisted of a gateway, a router and several sensor nodes. Each sensor node is made up of a transmitter and three sensor units to measure the soil, field and channel water quality, and the sensing data is accumulated in the cloud. The sensor provides high-precision analysis of conditions by utilising a uniquely shaped sensor element and a proprietary algorithm. It is able to run for over a year of continuous operation on three size AA batteries.