GroPoint Classic

The original analog GroPoint moisture sensor, with legendary ruggedness and accuracy.

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GroPoint™ Classic is our original analog soil sensor, with a rugged design that has been proven over decades of use. The sensing element is manufactured from a solid 7mm (0.28″) stainless steel rod, and all electronics are sealed in water-proof epoxy.

The 4-20mA output integrates easily with common irrigation control and management systems, and it’s also available with 0-5mA output. The standard 5m cable can be extended to up to 150m (500′) and terminates in a rugged IP66/68 environmental connector or bare wires.

The sensor features a larger area of influence than our other sensors—about 10cm (4″) surrounding the sensing element. It can be calibrated specifically for sandy soils, high salinity and clay soils or a broad range of soils. Please specify when ordering.

The GroPoint Classic responds immediately and accurately to changes in soil moisture. It’s extremely rugged, easy to install and requires virtually no maintenance, providing years of reliable service.

  • Fully potted electronics for excellent durability.
  • Stainless steel sensing element provides years of maintenance free, reliable sensing.
  • 4-20 mA interface provide easy and simple integration into common irrigation management and control systems. Also available with 0-5mA output.
Moisture
Measurement range 0% to 100% of VMC
Accuracy ±2.0% *
Precision < 0.2%
Electrical
Output 4-20 mA (optional 0-5mA)
Connection Bare wire
Optional EN3 3-pin IP66/IP68 rated environmental connector
Input voltage 5.5 to 18 VDC
Current consumption 0-5 mA: 15 mA (nominal), 20mA (max)
4-20 mA: 30 mA (nominal), 50 mA (max)
Environmental
Operating temperature -20°C to 70°C (-4°F to 158°F)
Storage temperature -40°C to 85°C (-40°F to 185°F)
Physical
Weight (with standard cable) 635 g (1.4 lb.)
Cable weight 38 g per m (0.42 oz. per foot)
Dimensions 26 cm x 8.9 cm x 4.4 cm (10.25” x 3.5” x 1.75”)
Standard cable 5 m (16.4 ft.) Max. 500 ft.
3xAWG22 dual-shielded, twisted pair, rated for direct burial
Warranty 1-year limited parts and labour

* 8% to 42% VMC, in controlled laboratory conditions; factory calibrated for most agricultural soils. In field applications, accuracy may slightly decrease due to the inevitable heterogeneity of soil texture, soil compaction, moisture and fluctuation in soil temperature. The accuracy may also decrease in difficult soil conditions (higher clay and salinity content). In normal conditions, GroPoint sensors will maintain their accuracy from permanent wilting through field capacity in sandy loam through clay soils with less than 60% clay particles. Under moderately saline conditions. GroPoint sensors will maintain their accuracy up to 6 ds/m.

  • GroPoint Profile and GroPoint Pro will work with virtually any data logger that supports the SDI-12 standard.

    GroPoint Lite and Classic will work with virtually any data logger. Just ensure your data logger will handle the output of your GroPoint Lite sensor (whether analog or digital).

  • No, GroPoint probes are meant to be used on a permanent or semi-permanent basis. There should be minimal disturbance of the surrounding soil for proper accuracy.

  • GroPoint probes can be used in virtually any soil.

  • GroPoint sensors feature an accuracy rating of ±2% (±0.02 m3m-3) volumetric soil moisture, between the range of 8% to 42% VMC (this is the normal range for agricultural applications). We obtain this accuracy through a patented technique which improves the performance of the already reliable TDT method of soil moisture measurement. This patented technology is called TDT5, which you can read about here.

    While a < ±1% accuracy rating is achieved in controlled laboratory conditions, GroPoint sensors are factory calibrated for most agricultural soils. In field applications, accuracy may slightly decrease due to the inevitable heterogeneity of soil texture, soil compaction, moisture and fluctuation in soil temperature. The accuracy may also decrease in difficult soil conditions (higher clay and salinity content). For these reasons we state a real-world accuracy of ±2%. In normal conditions, GroPoint sensors will maintain this accuracy from permanent wilting through field capacity in sandy loam through clay soils with less than 60% clay particles. Under moderately saline conditions, GroPoint sensors will maintain their accuracy up to 6 ds/m.

  • The GroPoint Classic sensing element will measure the differences in soil moisture up to 10 cm (about 4″) from the rods along all sides. A typical GroPoint measurement will interrogate an oval shaped area approximately 15 cm (6″) high x 23 cm (9″) wide x 37 cm (15″) long. The soil closely surrounding the rods will have a greater influence on the soil moisture reading than the soil about 8 cm (3″) away from the rods. The soil must be in direct contact with the rods to ensure an accurate reading.

  • GroPoint Classic sensors can be installed vertically or horizontally. Horizontal is the preferred method for a shallow sensor and vertical for sensors deeper than 30cm (12″). With a horizontal orientation, soil can be more easily packed around the elements, and this method also gives a more precise measurement of soil moisture in a specific range. In horizontal installation, the sensor will be measuring the soil moisture in an area about 7 cm (3″) above and below the sensor.

    With vertical placement, the sensor will report average soil moisture over it’s entire active length of 40 cm (16″). This may be the desired orientation for covering the majority of the root zone of a crop with one sensor.

    CAUTION: With this large active length, soil at the top could be dry and the bottom wet, resulting in a reading of good average soil moisture. With the roots concentrated in the dry topsoil, the crop could be unnecessarily stressed. Use the suggested vertical installation only when the crop roots have grown to cover the entire length of the sensor.

    Obtaining good soil compaction around the sensor is more difficult with a vertical installation. Make sure that there are no air pockets around the sensor elements when back filling the hole.

  • GroPoint sensors are furnished with a high quality cable suitable for direct burial or exposure to direct sunlight. It is resistant to damage from insects, abrasion and normal environmental exposure. However, mechanical damage from hoes, coyotes, gophers, other animals, and cultivators can easily cut this cable. Any problem with this sensor will most likely be due to damage to the electrical cable. To prevent damage, it is strongly recommended that the cable be installed in 3/4-inch electrical conduit. This size conduit is required to accommodate the passage of the plug connector.

  • For SDI-12 sensors, according to the SDI-12 specification, the combined length of all sensors connected to a data logger cannot exceed 610 m (2,000 feet). So one sensor with a 610 m cable or 10 sensors each with a 61 m cable.

    For analog sensors, the maximum length is 305 m (1,000 feet).

    It should be noted that the longer the cable is, the more susceptible the sensor is to catastrophic damage/failure due to increased voltage spikes from lightning strikes. A long cable becomes a very large antenna to amplify the voltage. Cable should be buried wherever possible.

    The minimum wire gauge when using a cable approaching the maximum should be 20 AWG.

  • Custom cable lengths can be ordered from us, or cable may be spliced by the customer. Each cable has three wires. The cable must be 22 gauge copper or larger.

    All connections should be made inside a waterproof box using silicone filled, waterproof, wire nut connectors. These waterproof connectors are available at local electrical/hardware suppliers, such as The Home Depot.

  • GroPoint has dealers in several international locations. You can find your local dealer on the Dealers page.

    GroPoint products are also sold online and we offer several self-help support resources, as well as unlimited support via phone, email and online chat.

General Inquiry
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  • GP-DL4 Data Logger

    $399.00$469.00

    Log soil data from up to 10 SDI-12 sensors or 4 analog sensors, for up to a year on standard household batteries. This simple data logger is no-frills, but effective and reliable.

    Select options
  • Measures soil moisture.
  • 4-20 mA interface provides easy integration into common irrigation management and control systems.
  • Also available with 0-5mA output.
  • Based on field-proven TDT soil moisture measurement, and features some aspects of our proprietary TDT5 technology.
  • Low power consumption—suitable for remote applications.
  • Comes with 5 m (16.4′) durable cable (4-pin IP68-rated EN3 connector optional).