Stevens HydraProbe User manual

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Soil Sensor
®
Installation Guide
Rev. IV
For Firmware Version 6.0

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Safety and Equipment Protection
WARNING!
ELECTRICAL POWER CAN RESULT IN DEATH, PERSONAL INJURY OR CAN CAUSE DAMAGE TO EQUIPMENT. If the instrument is driven by an external
power source, disconnect the instrument from that power source before attempting any repairs.
WARNING!
BATTERIES ARE DANGEROUS. IF HANDLED IMPROPERLY, THEY CAN RESULT IN DEATH, PERSONAL INJURY OR CAN CAUSE DAMAGE TO
EQUIPMENT. Batteries can be hazardous when misused, mishandled, or disposed of improperly. Batteries contain potential energy, even when partially discharged.
WARNING!
ELECTRICAL SHOCK CAN RESULT IN DEATH OR PERSONAL INJURY. Use extreme caution when handling cables, connectors, or terminals; they may yield
hazardous currents if inadvertently brought into contact with conductive materials, including water and the human body.
CAUTION!
Be aware of protective measures against environmentally caused electric current surges and follow the previous warnings and cautions, the following safety activities
should be carefully observed.
Children and Adolescents
NEVER give batteries to young people who may not be aware of the hazards associated with batteries and their improper use or disposal.
Jewelry, Watches, Metal Tags
To avoid severe burns, NEVER wear rings, necklaces, metal watch bands, bracelets, or metal identification tags near exposed battery terminals.
Heat, Fire
NEVER dispose of batteries in fire or locate them in excessively heated spaces. Observe the temperature limit listed in the instrument specifications.
Charging
NEVER charge "dry" cells or lithium batteries that are not designed to be charged.
NEVER charge rechargeable batteries at currents higher than recommended ratings.
NEVER recharge a frozen battery. Thaw it completely at room temperature before connecting charger.
Unvented Container
NEVER store or charge batteries in a gas-tight container. Doing so may lead to pressure buildup and explosive concentrations of hydrogen.
Short Circuits
NEVER short circuit batteries. High current flow may cause internal battery heating and/or explosion.
Damaged Batteries
Personal injury may result from contact with hazardous materials from a damaged or open battery. NEVER attempt to open a battery enclosure. Wear appropriate
protective clothing, and handle damaged batteries carefully.
Disposal
ALWAYS dispose of batteries in a responsible manner. Observe all applicable federal, state, and local regulations for disposal of the specific type of battery involved.
NOTICE
Stevens makes no claims as to the immunity of its equipment against lightning strikes, either direct or nearby.
The following statement is required by the Federal Communications Commission:
WARNING
This equipment generates, uses, and can radiate radio frequency energy and, if not installed in accordance with the instructions manual, may cause interference to radio
communications. It has been tested and found to comply with the limits for a Class A computing device pursuant to Subpart J of Part 15 of FCC Rules, which are designed
to provide reasonable protection against such interference when operated in a commercial environment. Operation of this equipment in a residential area is likely to cause
interference in which case the user at their own expense will be required to take whatever measures may be required to correct the interference.
USER INFORMATION
Stevens makes no warranty as to the information furnished in these instructions and the reader assumes all risk in the use thereof. No liability is assumed for damages
resulting from the use of these instructions. We reserve the right to make changes to products and/or publications without prior notice.

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Regulatory
Declaration of Conformity
The Manufacturer of the Products covered by this Declaration is
Water Monitoring Systems, Inc.
12067 NE Glenn Widing Dr. #106
Portland, Oregon 97220 USA
503-445-8000
The Directive covered by this Declaration2004/108/EC Electromagnetic Compatibility directive
The Product Covered by this Declaration
HydraProbe Soil Measurement Sensor
The basis on which Conformity is being Declared
The manufacturer hereby declares that the products identified above comply with the protection requirements of the EMC
directive for and following standards to which conformity is declared: EN61326-1:2006
Electrical requirements for measurement, control, and laboratory use EMC requirements Class A equipment –Conducted
Emissions and Radiated Emissions
1907/2006/EC REACH
Stevens Water Monitoring Systems, Inc. certifies that the Stevens HydraProbe, including all models and components, are compliant with the European
Union Regulation (EC) 1907/2006 governing the Registration, Evaluation, Authorization, and Restriction of Chemicals (REACH) and do not contain
substances above 0.1% weight of a Substance of Very High Concern (SVHC) listed in Annex XIV as of June 15th, 2019.
The technical documentation required to demonstrate that the products meet the requirements of the EMC directive has been
compiled and is available for inspection by the relevant enforcement authorities.
RoHS √

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Installation of The HydraProbe
See Appendix A for SDI-12 probes and Appendix B for RS485 Probes for wiring and communication.
Calibration is not necessary for most soils and the default settings will accommodate most users and
applications.
Supporting Documents
Document Number
Document
HP003A
HydraProbe Quick Start, SDI-12
HP004A
Soil Data Guide
HP005A
HydraProbe Install and Troubleshooting Guide
HP006A
HydraProbe Quick Start, RS-485
HP007A
Regulatory Information
HP008A
HydraProbe Comprehensive Manual
HP009A
Soil Geomorphology Guide for Soil Sensors
HP010A
Lightning Protection for Meteorological Stations

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Stevens HydraProbe Installation Guide
Table of Contents
1Introduction 7
Applications.................................................................................................................................8
Calibrations..................................................................................................................................8
Dielectric Permittivity .................................................................................................................8
Structural Components ................................................................................................................8
Accuracy and Precision ...............................................................................................................9
Electromagnetic Compatibility....................................................................................................9
Configurations and Physical Specification..................................................................................9
Soil Data Accessories and other Products .................................................................................10
1.8.1 Portable soil sensors.........................................................................................................10
1.8.2 Tempe Cell.......................................................................................................................11
HydraProbe Versions.................................................................................................................12
2Installation 14
Precautions.................................................................................................................................14
Topographical Station Placement Considerations.....................................................................14
Soil Sensor Depth Selection ......................................................................................................16
Installation of the HydraProbe in Soil .......................................................................................18
2.4.1 Checklist before you go into the field..............................................................................18
2.4.2 Test the probes and logger in the office before going into the field ................................18
2.4.3 Labeling............................................................................................................................18
2.4.4 Installing the HydraProbe in the Soil...............................................................................18
2.4.5 Soil Sensor Orientation ....................................................................................................19
Wiring to a Logger Station ........................................................................................................20
2.5.1 Sensor Setup.....................................................................................................................20
Backfilling the Hole...................................................................................................................20
2.6.1 Test Before you Backfill ..................................................................................................20
Lightning....................................................................................................................................21
3Troubleshooting and Soil Considerations 23
Troubleshooting at the logger end and out of the ground..........................................................23
3.1.1 Check Wiring and Power .................................................................................................23
3.1.2 Communicate with the Sensor at the Logger End............................................................23
3.1.3 Check the Logger Configuration......................................................................................24
3.1.4 Remove the Suspect Probe from the Soil.........................................................................24
Soil Hydrology...........................................................................................................................24
3.2.1 Evapotranspiration ...........................................................................................................25
3.2.2 Hydrology and Soil Texture.............................................................................................25
3.2.3 Soil Bulk Density .............................................................................................................25
3.2.4 Shrink/Swell Clays...........................................................................................................26
3.2.5 Rock and Pebbles .............................................................................................................26
3.2.6 Bioturbation......................................................................................................................26
3.2.7 Salt Affected Soil and the Loss Tangent..........................................................................27

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3.2.8 Ped Wetting......................................................................................................................27
3.2.9 Frozen Soil .......................................................................................................................28
Appendix A–HydraProbe SDI-12 Communication (6.0 Firmware) 29
Appendix B- HydraProbe RS-485 Communication (6.0 Firmware) 32
Appendix C–Custom Calibration Programming 35
Custom Calibration Procedure for the SDI-12 HydraProbe ...............................................................37
Custom Calibration Settings Procedure for the RS-485 HydraProbe.................................................39
Appendix D - Useful links 41

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1Introduction
The Stevens HydraProbe Soil Sensor, or the HydraProbe, measures soil temperature, soil moisture, soil electrical
conductivity (EC), and the complex dielectric permittivity. Designed for many years of service buried in soil, the
HydraProbe uses quality material in its construction. Marine grade stainless steel, PVC housing, and a high-grade
epoxy potting protects the internal electrical component from the corrosive and reactive properties of soil. Most
of the HydraProbes installed more than a decade ago are still in service today.
The HydraProbe is not only a practical measurement device; it is also a scientific instrument. Trusted by farmers
to maximize crop yields, using HydraProbes in an irrigation system can prevent runoff that may be harmful to
aquatic habitats, conserve water where it is scarce, and save money on pumping costs. Researchers can rely on
the HydraProbe to provide accurate and precise data for many years of service. The inter-sensor variability is low,
allowing direct comparison of data from multiple probes in a soil column or in a watershed.
The HydraProbe bases its measurements on the physics and behavior of a reflected electromagnetic radio wave
in soil to determine the dielectric permittivity. From the complex dielectric permittivity, the HydraProbe can
simultaneously measure soil moisture and electrical conductivity. The complex dielectric permittivity is related
to the electrical capacitance and electrical conductivity. The HydraProbe uses patented algorithms to convert the
signal response of the standing radio wave into the dielectric permittivity and thus the soil moisture and bulk soil
electrical conductivity.
HydraProbe installation at a typical USDA NRCS SNOTEL Site.
Picture compliments of USDA NRCS in Salt Lake City, Utah.

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Applications
The US Department of Agriculture Soil Climate Analysis Network (SCAN) has depended on the HydraProbe in
hundreds of stations around the United States and Antarctica since the early 1990s. The Bureau of Reclamation's
Agrimet Network, NOAA, and other mesonets and research watersheds around the world trust the measurements
the HydraProbe provides. Applications of the HydraProbe include:
Agriculture Irrigation
Viticulture Sports Turf
Research Soil Phytoremediation
Water Shed Modeling Evapotranspiration Studies
Land Reclamation Land Slide Studies
Shrink/Swell Clays Flood Forecasting
Satellite Ground Truthing Wetland Delineation
Predicting Weather Precision Agriculture
Calibrations
The HydraProbe has three factory calibrations that provide excellent performance in a variety of soils regardless
of organic content or texture. The three calibrations are: GENERAL (G) good for most all soils composed of
sand, silt, and clay; ORGANIC (O); and ROCKWOOL (R). The factory GENERAL soil calibration is the default
calibration and is suitable for most all mineral soils. (See Chapter 5.4.3 and Appendix C for more information)
Dielectric Permittivity
The complex dielectric permittivities are provided for custom calibrations and other applications. (See Chapter
4.2.2 for more information)
Structural Components
There are three main structural components to the HydraProbe: the tine assembly, body, and cable. The marine
grade stainless steel tine assembly is the four metal rods that extend out of the base plate ground plane and is the
wave guide. Each tine is 58 mm long by 3 mm wide. The base plate is 25 mm in diameter. Electromagnetic waves
at a radio frequency are transmitted and received by the center tine. The head, or body of the probe, contains the
circuit boards, microprocessors, and other electrical components. The outer casing is PVC and the internal
electronics are permanently potted with a rock-hard epoxy resin giving the probes a rugged construction. The
cable has a direct burial casing and contains the power, ground, and data wires that are all soldered to the internal
electronics.

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Accuracy and Precision
The HydraProbe provides accurate and precise measurements. Table 1.1 below shows the accuracy.
Parameter
Pro/ ET Version
Real Dielectric
Permittivity (isolated)
Range: 1 to 80 where 1 = air, 80 = distilled water
-Accuracy: < +/- 0.5% Or +/- 0.25 dielectric units
Imaginary Permittivity
Range: 0 to 80 where 1 = air, 80 = distilled water
Accuracy: +/- 0.1 up 0.25 S/m and +/-7 at or above
0.5 S/m
Soil Moisture for
inorganic mineral soils
Range: From complete dry to full saturation (0% to
100% of saturation)
Accuracy1: +/-0.01 WFV for most soils (m3,m-3)
+/- 0.03 for fine textured soil
Bulk Electrical
Conductivity (EC)
Range: 0 to 1.5 S/m
Accuracy2: +/- 2.0% or 0.02 S/m whichever is greater
Temperature
Range: -10 to 60oC
ET Range: -30 to 65oC
Accuracy: +/- 0.3oC
Inter-Sensor Variability
+/- 0.012 WFV
Pore Water EC
Hilhorst Equation
Table 1.1 Accuracy and Precision of the HydraProbes’ Parameters.
1Soil Moisture accuracy can vary with soil properties.
2Accuracy and range of Bulk EC depends on soil properties and distribution of ions present.
Electromagnetic Compatibility
The Stevens HydraProbe is a soil sensor that uses low power RF energy. The intended use of the HydraProbe is
to be buried in soil underground to depths ranging from 5 cm to 2 meters deep.
The HydraProbe meets and conforms to the conducted emissions criterion specified by EN 61326-1:2006 and
FCC 15.107:2010 in accordance with method CISPR 11:2009 and ANSI C63.4:2009
The HydraProbe meets the non-intentional radiator emissions, (group A) specified by EN 61326-1:2006, FCC
15.109(g) and (CISPR 22:1997):2010 in accordance with method CISPR 11:2009 and ANSI C63.4:2009 when
the probe is NOT buried as specified. Test results are available upon request. The HydraProbe is RoHS.
Configurations and Physical Specification
The HydraProbe is available in available in both SDI-12 and RS-485, with standard cable lengths of 7.5, 15, and
30 meters.
The two digital formats, SDI-12 and RS-485, incorporate a microprocessor to process the information from the
probe into useful data. This data is then transmitted digitally to a receiving instrument. SDI-12 and RS-485 are

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two different methods of transmitting digital data. In both versions there are electrical and protocol specifications
that must be observed to ensure reliable data collection.
All configurations provide the same measurement parameters with the same accuracy. The underlying physics
behind how the HydraProbe works and the outer construction are also the same for each configuration. Table 1.2
provides a physical description of the HydraProbe.
Feature
Attribute
Probe Length
12.4 cm (4.9 inches)
Diameter
4.2 cm (1.6 inches)
Sensing Volume1
(Cylindrical measurement region)
Length 5.7 cm (2.2 inches)
Diameter 3.0 cm (1.2 inches)
Weight
200g (cable 80 g/m)
Power Requirements
7 to 20 VDC (12 VDC typical)
Storage Temperature Range
-40 to 75°C
Table 1.2 HydraProbe Physical Description (All Versions)
1The cylindrical measurement region or sensing volume is the soil that resides between the stainless-steel
tine assembly. The tine assembly is often referred to as the wave guide, and probe signal averages the soil
in the sensing volume.
Soil Data Accessories and other Products
1.8.1 Portable soil sensors
Figure 1.1. The portable HydraGO-FLEX and HydraGO-S allow for wireless on the go measurements of soil moisture.
Connect via Bluetooth with a smartphone and the HydraGO App.
There are two portable HydraProbe soil sensor systems, the HydraGO-FLEX and the HydraGO-S. Each model
of the HydraGO has Bluetooth and can connect to a mobile device. The HydraGO App will work with either
Android or Apple iOS devices. The HydraGO-S provides GPS data from the device’s GPS which has a typical
accuracy of 5 to 10 meters depending on the device. The HydraGO FLEX has an internal survey grade GPS,