+ General
Is the GroPoint Profile compatible with all data loggers?
GroPoint Profile will work with virtually any data logger that supports the SDI-12 standard.
Can the GroPoint Profile be used as a portable solution?
GroPoint Profile is for permanent or semipermanent installations only. The soil moisture probe should not be briefly placed in the ground to ensure proper accuracy. It performs best and with the highest soil moisture accuracy when the soil has fully settled around the probe. 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 to monitor soil moisture throughout your site.
Does temperature come standard with the GroPoint Profile
Yes, the standard configuration for GroPoint Profile is with temperature sensing capabilities. However, the GroPoint Profile comes in two versions; Volumetric Soil Water Content and Soil Temperature Sensing or Volumetric Soil Water Content Sensing. Please specify which configuration suits your needs when placing an order.
What kind of soils can the GroPoint Profile be used in?
The GroPoint Profile can take measurements of virtually any soil type. We have an extensive calibration procedure that allows us to factory-calibrate the soil moisture probes for most soil types. Customers can also perform their own calibrations after they receive their GroPoint Profile.
I’m not in BC or Canada. Can I buy and obtain support for GroPoint products locally?
GroPoint has dealers in several international locations. You can find your local dealer on the Dealers page.
GroPoint soil probes and data loggers are also sold online and we offer several self-help support resources, as well as unlimited support via phone, email and online chat.
What is the area of influence, or measurement volume, of the GroPoint Profile?
GroPoint Profile detect water as much as 5 cm (2 inches) from the surface of the probe fins and 2 L volume of influence per 15 cm segment. Like all dielectric based sensors, moisture closest to the surface of the soil moisture 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 further away.
The slide hammer is quite expensive to ship to the US from Canada. Can I purchase it from and ship it within the US?
Our longtime partner, and the manufacturer of the slide hammer, AMS (based in Idaho), sells it on their website. Here is a link to the product page.
Does the RS485 protocol use Modbus RTU to connect to sensors?
Yes, the GroPoint Profile can be configured for Modbus over RS-485 and SDI-12 over RS485.
+ Calibration & Accuracy
Can you explain your calibration process for the GroPoint Profile?
Our calibration process is extensive, involving multiple reference solutions with different dielectric constants in 6 inch diameter columns. Each segment is individually calibrated to match a reference % moisture content. The process is time-consuming but very accurate, and very repeatable against a reference.
Does it need to be calibrated for different soil types?
GroPoint soil 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
Custom calibration can be done at our facility upon request. End customers can also perform their own calibration (documented in the User Manual).
If I use a sensor calibrated for a different type of soil than I have, will I lose accuracy?
If you’re using a sensor with the wrong calibration, measurements will have a small absolute error, read either too high or too low by up to 4%.
My soil horizons span sandy, loamy and clay mixtures. Can each segment be calibrated differently to more accurately measure the different soil horizons?
Yes! Each segment can be calibrated for different soil horizons via SDI-12 extended commands entered through a small software utility.
What is TDT5 ? How does it differ from other soil measurement methods?
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:
- 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.
- Filtering 400,000 pulses for each measurement – boosts accuracy to ±2% and repeatability to < 0.2%
- Captures measurement in less than 100ms – reduces power consumption
- Embeds antenna and circuitry on a single board – dramatically reduces cost to manufacture
- Encases entire sensor in a durable, sealed polycarbonate housing – maximizes durability
Learn more about TDT5 here.
What is the difference between TDT and capacitance methodologies for measuring soil moisture? Are there any distinct advantages of TDT over capacitance?
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).
Are there any issues with compaction around the sensor when the pilot rod is inserted? Won’t this change the water content values being read?
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
How deep in the soil should the GroPoint Profile be placed?
These sensors are intended to have the top of the probe near the surface of the soil with the length of the probe determining the lowest depth of the soil moisture and temperature points.
Can the sensor cable be buried, and is it durable enough to be left exposed on the surface of the ground?
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.
What is the maximum length of cable that can be used with the sensor?
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.
If you are interested in getting rid of the cable, check out this link. https://www.gropoint.com/products/wireless
Can I use my own cable to extend the length of the standard cable?
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.
After inserting the GroPoint Profile into the hole created by the pilot rod, will there be any air gaps between the soil and the probe that will affect the accuracy?
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.
Will I really be able to drive the pilot rod into hard, dry, compacted clay soils with the slide hammer? And even if I do, are you sure I’ll be able to get it out again?
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!)
