GroPoint Profile

Multi-segment soil moisture and temperature profiling probe

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GroPoint™ Profile provides cost-effective measurement of volumetric water content over multiple depths using a single probe, eliminating the cumbersome excavation required for multiple sensors placed at different depths. It can be deployed in irrigation-sensitive zones to enable full control of precision irrigation needs, providing an understanding of water movement through the soil.

The sleek, lightweight design installs quickly with minimal soil disruption using a pilot rod and slide hammer tool. Designed for vertical installation, the sensor takes measurements over multiple soil layers, with each measurement zone (segment) providing the average volumetric soil moisture content over a 15 cm range (approximately 6 inches).

Unlike any other soil profiling probe, GroPoint Profile provides true soil profiling quantification, measuring the average moisture across the entire length of each segment (15cm or 6″), because there are no gaps between segments. This unique feature allows measuring the water movement through the soil continuously, rather than just at discrete positions on the probe.

The Most Accurate and Cost-Effective Soil Profiling Solution Available

  • Eliminates need for multiple sensors and cabling systems.
  • Measures across the entire length of the probe, averaging the soil moisture and temperature in each segment
  • Installs quickly and easily without excavating.
  • One SDI-12 address is used to read all segments, providing for simplified installations. Optional RS-485 output.
  • Moisture readings can be user-calibrated with 3rd-order polynomials to meet custom requirements.
  • Low power requirements—suitable for remote, autonomous applications.
  • Patented TDT5 technology for scientific-grade accuracy and excellent long-term stability of measurements.
  • Fully potted electronics for excellent durability.

Configurations

GroPoint Profile is available in six different multi-segment lengths, suitable for a wide range of agricultural crop monitoring.

You can also choose from two different configurations for temperature sensors, depending on your requirements. You can configure it with no temperature sensors if you only require moisture measurement, or the standard configuration places temperature sensors every 1 or 2 segments.

Choose the number of 15 cm (6″) segments that are right for your application. Custom lengths also available.

2
3
4
5
6
8

x segments

Moisture
Measurement range 0% to 100% of VMC
Accuracy ±2.0% *
Precision < 0.2%
Temperature
Measurement range -20°C to +70°C (-4°F to 158°F)
Accuracy ±0.5°C
Electrical
Output SDI-12 V1.3 (RS485 optional)
Connection Bare wire (optional 4 pin, IP66/IP68 rated environmental connector)
Input voltage 6 to 14 VDC max. 18 VDC
Current consumption Quiescent: Active: 15-20 mA (depending on number of segments) for 100 mS
Warm-up time on power up
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
Length Each segment is approximately 15 cm (5.9") long. Total length is the number of segments multiplied by 15 cm. For example, a 3-segment probe is about 45cm long.
Probe weight 2 segments: 292 g (10.3 oz.)
3 segments: 351 g (12.4 oz.)
4 segments: 408 g (14.4 oz.)
5 segments: 468 g (16.5 oz.)
6 segments: 526 g (18.6 oz.)
8 segments: 642 g (22.6 oz.)
Cable weight 38 g per m (0.42 oz. per foot)
Standard cable 5 m (16.3 ft.)
4xAWG22 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.

General

  • 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).

  • GroPoint Profile is for permanent or semipermanent installations only. For proper accuracy it must be installed properly, not just poked in the ground for a quick reading. However, given the ease of installing (no excavation required, no access tube required) and its low price point relative to other soil profiling sensors, there’s little reason not to use permanent GroPoint Profile installations for monitoring soil moisture throughout your site.

  • GroPoint probes can be used in virtually any soil.

  • 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.

  • GroPoint Profile probes detect water as much as 5 centimetres (2 inches) from the surface of the probe fins although, like all dielectric based sensors, moisture closest to the surface of the probe has more influence on the readings than moisture further away so that soil closely surrounding the sensor will have a greater influence on the soil moisture reading than the soil.

  • No, it doesn’t use Modbus, but SDI-12 over RS485.

Calibration & Accuracy

  • Our calibration process is extensive, involving multiple reference dialectric solutions in 6 inch diameter columns. Each segment is individually calibrated to match a reference EC. The process is time-consuming but very accurate, and very repeatable against a reference.

  • GroPoint probes are factory-calibrated for use in most soils. There are also two other standard calibrations that can be used, which you can specify when you order. Below is an image of a standard soil texture triangle. By default, calibration is done for a wide variety of soil types represented by the red area. You can also request that your sensor is calibrated for clay or highly saline soil (the green area) or sandy soils (blue area).

    Custom calibration can be done at our facility upon request. End customers can also perform their own calibration (documented in the User Manual).

  • If you’re using a sensor with the wrong calibration, measurements will have a small absolute/relative error, read either too high or too low by up to 4%.

  • Yes! Each segment can be calibrated for different soil horizons via SDI-12 extended commands entered through a small software utility.

  • TDT5 is a proprietary technology based on Time Domain Transmission (TDT), which is a refined version of Time Domain Reflectometry (TDR). TDT measures the time taken for an electromagnetic wave to propagate (travel) along a given length of a transmission line in the soil. Moisture in the soil changes the soil’s dielectric properties, so that the electromagnetic wave travels at different rates in wet soil compared to dry soil. This allows for the accurate determination of soil moisture content.

    However, we add our own engineering designs that result in a less expensive, more robust and more accurate (with greater repeatability) sensor than with pure TDT alone. This enhances TDT in five (hence “TDT5“) key ways:

    1. Measures with an antenna 5 times longer than the physical length of the probe, which reduces the impact of noise, and provides an average across the entire length of each segment of the probe.
    2. Filtering 400,000 pulses for each measurement – boosts accuracy to ±2% and repeatability to < 0.2%
    3. Captures measurement in less than 100ms – reduces power consumption
    4. Embeds antenna and circuitry on a single board – dramatically reduces cost to manufacture
    5. Encases entire sensor in a durable, sealed polycarbonate housing – maximizes durability

  • Capacitance probes set up an oscillating circuit that has a different frequency of oscillation depending on the moisture content, whereas TDT (Time Domain Transmission) measures the time taken for an electromagnetic wave to travel along a given length of a transmission line in the soil. Both are affected by the soil’s dielectric properties, so the frequency of oscillation (capacitance) or the travel time (TDT) is related to the moisture content.

    One of the drawbacks of the capacitance method is that the frequencies involved are usually fairly low (less than 500kHz). If they weren’t, the current consumption (which is directly related to frequency, that is, higher frequency means higher current) would be fairly high. The issue is that at these relatively low frequencies the measurement is quite negatively affected by conductivity, which leads to a lot of variability in the readings (poor accuracy). TDT frequency bandwidths are much higher, on the order 500 MHz (i.e. 1000 times higher) and up. Therefore they are not nearly as susceptible to electrical conductivity.

    An advantage of TDT is that antennas can be constructed that measure the soil moisture over a large area. This is exactly what permits the GroPoint Profile to measure soil moisture over the entire length of the probe, averaging each 15cm (6″) segment. Capacitance probes, because of their physical construction, will only provide point measurement (measuring only at the point where sensors are located).

  • Some compaction will occur, but it is very minor and after 1-2 weeks of normalization the soil settles back. The GroPoint Profile is generally deployed in longer term deployments, not in singular reading environments where immediate insertion and extraction is the goal. As such, any influence of soil compaction during installation over the lifetime of the sensor deployment is negligible.

Installation

  • 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.

  • The pilot rod is specially designed and manufactured to create a pilot hole that exactly matches the dimensions of the GroPoint Profile. During installation, it is important that the pilot rod installation is done properly and that the pilot rod is inserted vertically using the slide hammer and that the pilot rod is not tilted back and forth. When the proper installation process is followed carefully, there will be very good soil contact and no air gaps.

    In the event of an improper installation, where the pilot rod is moved side-to-side during hammering, the pilot hole will be too large (larger near the top than at the bottom), and those gaps will take some time to close. The soil will take a few days to a week to fully settle back and seal 100% against the probe surface. You could also create a soil slurry at the surface to correct for improper installation.

  • Since the slide hammer provides weight for insertion and extraction, installing even a long (5 or 6-segment) GroPoint Profile into hard clay soils is not a problem. It is laborious, but the slide hammer does most of the work for you. The upward swing carries with it the momentum of the  slide hammer’s weight, and as such the pilot rod does work its way out. We have deployed in many clay soils—our GroPoint Profile installation tutorial video was shot in a region with fairly hard clay soil (see video below). You’ll see that the pilot rod seems to go in and come out effortlessly (although it wasn’t completely without effort!)

Datasheets

Other

This machining drawing will allow you to have the pilot rod (used to install a 4-, 6- or 8-segment GroPoint Profile probe) manufactured locally.

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  • Soil moisture profiling probe
  • Optional temperature measurement
  • SDI-12 interface
  • Based on our unique TDT5 technology.
  • Comes with 5 m (16.4′) durable cable (4-pin IP68-rated EN3 connector optional).
  • Factory-calibrated for most agricultural soils, but can be custom calibrated before shipping—request when ordering.
  • Sensor can be custom calibrated by the customer—see detailed procedure in the User Manual.

Videos

Introduction to GroPoint Profile
NEW!

A brief introduction to the GroPoint profile.

How to Install the GroPoint Profile

Here’s a detailed look at the process of installing a GroPoint Profile soil sensor. It’s not difficult (especially because there’s no excavation required) but we show you several tips and tricks for making your installation as smooth as possible so you can ensure you get high accuracy.

Measuring Across the Entire Probe Length
NEW!

In this video we discuss a unique aspect of the Gropoint Profile and how it contributes to greater accuracy by minimizing the effect of rocks, air pockets, and different soil horizons that are in the measurement area.

Installing a GroPoint Profile probe is quick and easy with no excavation required. Attach the slide hammer to the sturdy steel pilot rod.

Slide the top segment of the slide hammer up as much as it goes, then down forcefully. It will strike the bottom segment and drive the attached pilot rod into the soil.

The hole will be the exact size of the probe, so not only is there minimal disruption to the surrounding soil, there will be no air gaps between the probe and the undisturbed soil. This clever design further increases measurement accuracy.

The slide hammer is used to extract the pilot rod again, with a couple of quick upward movements (like hammering in reverse).

This single 4-segment probe is equivalent to 4 separate probes, each measuring the average moisture across 15cm (6"). Soil moisture is measured at 4 different depths simultaneously.

Each segment averages the volumetric moisture content measured over 15 cm (6"). Together, the range covered is the length of the entire probe, with no gaps between.

Analyze water movement
through the soil

Why is it the Best Profiling Probe for Irrigation Optimization?

GroPoint Profile is the only soil moisture probe that measures the entire volumetric moisture content surrounding the

Imagine this is the soil we want to measure for moisture content, from the surface to a depth of about 42 cm.

Like most soil, it's not completely uniform, with objects like this buried rock, air gaps from rodent tunnels and other things that affect moisture in the soil.

Throughout the soil horizons, there are also varying degrees of porosity and different soil densities.

GroPoint Profile

3-segment probe

45cm long

Other profiling probe

4 sensors every 10 cm

40cm long

The sensors of typical profiling probes measure only at that point.

The GroPoint profile's sensor segments measure the entire length of each segment (and therefore the entire probe length).

This sensor will measure less moisture than there actually is because the rock consumes a large portion of the sensor's measurement area.

The rock will have minimal impact on the GroPoint Profile's measurements.
WHY?
Because the soil moisture content across the full 15cm length of each segment is measured and averaged.

More precision,

GroPoint's patented technique for soil moisture measurement

Our proprietary TDT5 technology delivers an exceptional price:performance ratio, with performance as good (in most cases better) as sensors costing much more.

 

How does it work?

GroPoint™ sensors are based on the field-proven Time Domain Transmission (TDT) method of reliably measuring soil moisture, which is a refined version of Time Domain Reflectometry (TDR).

TDT-based sensors do not need to be calibrated to each type of soil they will be buried in to deliver excellent accuracy and stability, however we do calibrate for 3 specific soil types for even greater accuracy.

TDT5 enhances TDT in 5 key ways.