WET150: The Multi-Parameter Soil Sensor

Delta-T Devices has introduced a new digital multi-parameter WET150 soil sensor that represents the culmination of its four decades of research and development.

Through several major design breakthroughs, the sensor provides research-grade precision as well as build quality at a price point that was not previously possible.

The WET150 is the perfect sensor developed to analyze soil conditions and is also suitable for integrating into SDI-12 horticultural and environmental control/measurement systems.

  • The latest lower-cost, research-grade multi-parameter sensor
  • Digital SDI-12 for simple system integration
  • Quantifies electrical conductivity, temperature and moisture
  • Precise monitoring of growing conditions
  • Buriable, robust and low power
  • Five-year warranty
  • Extendable and detachable cable system

Video — The Wet150 Sensor’s Use in Research and Horticulture

WET150 Sensor video (SDI-12 soil and substrate moisture sensor - also measures EC and temperature)

Video Credit: Delta-T Devices Ltd

A Digital SDI-12 Sensor that Measures Three Crucial Variables

When the WET150 sensor is concealed in substrate or soil, it simultaneously quantifies three major variables that affect the growth of plants. These variables include temperature, moisture content and electrical conductivity (EC) — a powerful indicator of the general level of nutrients.

One of the major strengths of the WET150 sensor is its potential to consistently estimate pore water conductivity (ECp) — the ion content of the water available to the plant.

The patented sensor electronics of the WET150 provide research-grade measurement precision with excellent temperature stability and salinity — both important for crucial control and irrigation decisions. When the WET150 sensor is buried, temperature measurement — which is necessary for offsetting the EC measurement to achieve optimum precision — is directly obtained from the root zone.

Accurate Monitoring of Soil and Substrate Conditions

When the WET150 sensor is installed in growing media, it can offer the precise information needed to fuel effective SDI-12-enabled automatic environmental control and precision irrigation systems — allowing decreased use of fertilizer/water while enhancing quality and yields of produce.

Besides this, the robust watertight design of the WET150 sensor makes it perfect for use in outdoor farming and field studies — sensors can be left buried across extended periods of time without affecting the performance. The WET150 sensors can even be buried at varying depths for tracking EC profiles, soil moisture and temperatures.

Digital SDI-12 Interface

The WET150 is essentially a digital SDI-12 sensor that completely conforms to SDI-12 version 1.3 standards. SDI-12 is a standardized interface for linking digital sensors to a master device, usually an SDI-12 compatible wireless node, data logger, computer or controller. It defines both the sensor power and digital communications standards.

A major strength of the SDI-12 sensor is that it is capable of supporting the connection of numerous networked sensors to a solo input on an SDI-12-enabled master device. This reduces both costs and complexity.

The WET150 sensor, similar to all SDI-12 sensors, is low-power and includes a built-in microprocessor that allows it to carry out two-way communication with an SDI-12 master device.

The WET150 sensor outputs readings in a regular SDI-12 format, and these readings can be transmitted to, and detected by, the master device. Moreover, the integration of a microprocessor in the sensor gives the WET150 the potential to execute intricate internal correction, averaging algorithms and compensation that improve data quality.

The SDI-12 process is built on a master-slave configuration. When deployed in an SDI-12 network, the master device sends data requests to separately addressed WET150s (slaves). Such requests briefly trigger all the WET150 sensors in the network and cause a measurement and data-sending response from the targeted WET150 sensor. When there is no response to a master request, all the WET150 sensors stay in a dormant energy-saving state.

The Key Benefits of SDI-12

  • Several sensors can be used with only a single master device, thus decreasing costs and complexity
  • Several parameters can be transmitted across simplified wiring
  • Low-power systems operate on batteries and are powered through the interface Bus
  • Perfect for wireless communications-based applications
  • Accuracy is not lost across large cable runs 

Cables and Connectors

The WET150 sensor has a high-quality, stainless steel IP68-rated connector (M12 x five-way)—linking to the regular Delta-T range of M12 x five-way cables and accessories.

WET150 sensor cable options

Image Credit: Delta-T Devices Ltd

GP2 SDI-12 Data Logger — An Ideal Partner for the WET150

The WET150 sensor can be used with the SDI-12-enabled GP2 Data Logger and Controller featuring simple point and click configuration. A total of 62 WET150 sensors can be linked to a solo GP2 SDI-12 Data Logger (subject to the requirements of cable length and power).

Apart from SDI-12 input, the GP2 can also log 12 analog channels. The SDI-12-enabled GP2 Data Logger and DeltaLINK allow easy and rapid development of sensor networks without having to resort to the usually complex programming techniques that are often used by other manufacturers.

Thanks to the flexibility of the GP2 Logger and the SD1-12 interface, numerous power and cabling configurations can be made when constructing a sensor network. For more data, customers can refer to the WET150 User Manual. Alternatively, they can contact Delta-T Devices to discuss their applications in more detail.

Easy Installation

The strong and sharp pins of the WET150 sensor reduce disturbance to substrate and soil, maintaining the original structure around the measurement rods, rendering it easy to insert and install the probe. For in-depth burial, the cylindrical shape eases the installation in augured holes. Extension tubes, provided as an option, enable placement and removal (100 and 50 cm lengths, connectable).

Applications

Soil science — The WET15 sensor can be effortlessly incorporated into SDI-12 systems and provides research-grade reliability and precision for scientists tracking the conditions of soil and substrates. General areas of application include crop trials, irrigation research, forestry, soil water profiling, phenotyping and hydrology.

Horticulture and agriculture — The WET150 sensor comes with a complete set of calibrations and offers an effective, simple and robust solution to inspect the uniformity of growing conditions for several types of growing media. The WET150 sensor excels in quantifying the variables needed to track and regulate fertigation. It is also a robust device for sampling the levels of soil salinity (which can impact crop yields).

Precision irrigation — The WET150 sensor is perfect for precision irrigation applications. Thanks to its compact design, the sensor can be easily integrated into grow bags. The precise sensor data of the WET150 sensor can be used to drive an SDI-12-enabled automatic irrigation system or to improve irrigation scheduling.

System integration — The WET150 sensor has low power, simple SDI-12 output, and stable and precise three-parameter measurement, which make it the perfect sensor for system integrators. UV-resistant, industrial-rated, equipped with a waterproof IP68 connector enables the WET150 sensor to be buried for an indefinite period of time, while still allowing easy cable exchange or extension, if needed.

Data Logging and Portable Readout

The WET150 is also a dual-purpose soil moisture sensor. This means it can be deployed in substrate or soil and linked to an SDI-12 master device (for example, data logger) to offer long-term moisture, EC and temperature data.

Alternatively, the sensor can be utilized in kit form as a mobile sensor linked to the WET150 readout meter to take immediate spot measurements of EC and moisture content (when utilized in portable mode, the WET150 sensor does not indicate temperatures).

Calibrations

The WET150 sensor now comes complete with calibrations for organic and soils, in addition to coir, peat, perlite and mineral wool substrates soils.

WET150 Sensor Development Collaboration with National Physical Laboratory (NPL)

Measurement technologies designed by the renowned National Physical Laboratory (NPL) in the United Kingdom have played a crucial role in the development of the WET150 sensor.

The NPL’s involvement in the project is centered around the challenges of calibrating a sensor that concurrently quantifies both the permittivity of soil and the conductivity of soil (EC) — from which readings of soil moisture are produced.

The joint study between NPL and Delta-T Devices helped develop the latest dielectric fluids with conductivity and permittivity characteristics that are representative of those usually found in soils and soil-free growing media.

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