Related Manuals for Stevens Hydra Probe II Series
Summary of Contents for Stevens Hydra Probe II Series
- Page 1 Stevens Water Monitoring System, Inc. ® ® The Hydra Probe Soil Sensor Comprehensive Stevens Hydra Probe Users Manual 92915 July 2007...
- Page 2 CAUTION! Be aware of protective measures against environmentally caused electric current surges. Read the Stevens Engineering Applications Note, Surge Protection of Electronic Circuits, part number 42147. In addition to the previous warnings and cautions, the following safety activities should be carefully observed.
- Page 3 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:...
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Page 4: Table Of Contents
Comprehensive Stevens Hydra Probe II User's Manual Table of Contents Introduction Applications ..........................6 Temperature Corrections ......................7 Calibrations..........................7 Dielectric Permittivity .........................7 Structural Components ........................7 Accuracy and Precision .......................7 Configurations of the Hydra Probe Digital Probes ..........................8 2.1.1 Addressing & Programming....................9 2.1.2 Daisy Chaining Versus Home Run Wiring ................9... - Page 5 4.1.5 Diode Temperature......................26 Soil Temperature ........................27 Soil Moisture ..........................27 4.3.1 Soil Moisture Units ......................27 4.3.2 Soil Moisture Measurement Considerations ..............28 Soil Salinity (g/L NaCl)......................29 Soil Electrical Conductivity (Temperature corrected)...............30 Theory of Operation Real and Imaginary Dielectric Constants ..................31 Real Dielectric and Imaginary Constants (Temperature corrected) ..........33 Soil Electrical Conductivity.......................33 5.3.1 Electrical Conductivity Pathways in Soil.................33...
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Page 6: Introduction
Introduction The Stevens Hydra Probe Soil Sensor measures soil temperature, soil moisture, soil electrical conductivity and the complex dielectric permittivity. Designed for many years of service buried in soil, the Hydra Probe uses quality material in its construction. Marine grade stainless steel, ABS housing and a high grade epoxy potting protect the internal electrical component from the corrosive and the reactive properties of soil. -
Page 7: Temperature Corrections
Temperature Corrections The Hydra Probe’s soil moisture and electrical conductivity measurements are temperature corrected providing temperature independent data year round. Calibrations The Hydra Probe has four calibrations that provide excellent performance in most mineral soils regardless of texture or organics. The calibrations are sand, silt, clay and loam. The loam soil calibration is the default calibration and is suitable for Silt Loams, Loam, Clay Loam, Silty Clay Loam, Sandy Clay Loam, Sandy Loam, and some medium textured clays. -
Page 8: Configurations Of The Hydra Probe
Configurations of the Hydra Probe The Hydra Probe is available in three versions, differentiated by the manner that information is transferred. SDI-12 RS-485 Analog The two digital versions (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. -
Page 9: Addressing & Programming
2.1.1 Addressing & Programming The digital versions of the Hydra Probe (the SDI-12 and RS-485 versions) can be connected in parallel so that multiple probes can be connected to a single communications port of a data logger or other device. When multiple probes are connected this way, each probe must be assigned a unique address before they are installed. -
Page 10: Digital Rs-485 Hydra Probe Ii
Power Requirements 9 to 20 VDC (12VDC Ideal) Red Wire +Volts Power Input Black Wire Ground Blue Wire SDI-12 Data Signal Baud Rate 1200 Power Consumption <1 mA Idle, 30 mA Active Table 2.2 Digital SDI-12 Hydra Probe II Information. 2.1.4 Digital RS-485 Hydra Probe II Like the SDI-12 Hydra Probe, the RS-485 probe is also digital. -
Page 11: Analog Hydra Probe
The four voltage data wires need to be wired into four separate voltage sensing connection points on the recording instrument. On the Stevens DOT Logger, the analog ports are labeled A1, A2, A3, and A4. Use the logger data acquisition procedure to obtain the... -
Page 12: Post Possessing Raw Voltages Into The Measurements Of Interest
V2 and V3 will be between 0 and 2.5 volts DC. V4 will be between 0.1 to 0.8 volts DC. These 4 voltages need to be processed by a series of algorithms to obtain the parameters of interest. Stevens provides two executable programs to perform these calculations: HYDRA.EXE HYD_FILE.EXE. -
Page 13: Trouble Shooting The Analog Hydra Probe
Is the computer on the proper COM port? What about the Baud rate? Does the logger need a NUL modem or optical isolator in order to be connected to a computer? Most of the technical support questions Stevens receives are not due to malfunctioning probes but rather an incorrect data logger setup. -
Page 14: Frozen Soil
calibrate the probe accordingly. The calibration curves will mathematically have the appearance of equation [2.1] or [2.2] θ = A + BE + CE [2.1] θ = AE [2.2] Where θ is moisture E is the real dielectric permittivity and A,B,C, and D are coefficients. If the user wishes to use the Hydra Probe to measure moisture in a matrix that is not mineral soil, the user must empirically and experimentally solve equation [2.1] or equation [2.2]. -
Page 15: Installation
Table 2.4 in section 2.4.3 shows the wiring scheme for the Analog Hydra Probe. The four voltage data wires need to be wired into four separate data ports on the logger. On the Stevens DOT Logger, the analog ports are labeled A1, A2, A3, and A4. The red power wire should be... -
Page 16: Sdi-12 Hydra Probe Wiring Connections
+12 volt DC power supply, connect the black wire to a ground, and connect the blue wire to the SDI-12 port or the Data Logger. The SDI-12 data port on the Stevens DOT logger is conveniently located on the right side of front face plate. The advantage of SDI-12 communications is that multiple probes can be connected to a single port on data logger. -
Page 17: Soil And Topographical Considerations
Soil and Topographical Considerations 3.3.1 Soil Moisture Calibration There are four calibration curves depending on the texture of the soil. The calibrations curves are polynomials that include the real dielectric permittivity and several coefficients (Topp 1980, Seyfried and Murdock 2004). The four user selectable soil texture settings are Sand, Silt, Clay, and Loam. -
Page 18: Soil Classifications
If you have a mixture of sand, silt and clay or if you are unsure what the texture of your soil is, then use the Loam setting. The Sand, Silt and Clay settings are only suitable for soils that are comprised almost entirely of that one material. -
Page 19: Installation Of The Hydra Probe In Soil
Taxonomy. In this system, all of the worlds’ soils are broken into 12 orders based on climate, topography, biology and soil chemistry. Table 3.2 lists the orders. The Hydra Probe can accommodate all of the soil orders. Andisols, gelisols and histosols are soil that may have soil moistures and properties that depart from the Hydra Probe’s built in calibration curves. - Page 20 Figure 3.3 Groundwater pathways and Surface water. Taken from USGS Report 00-4008 Figure 3.4 Groundwater flow direction and surface water body. Taken from USGS report 00-4008. Figures 3.3 and 3.4 illustrate subsurface water movement in the water table. The Hydra Probe data is most meaningful in the unsaturated zone where soil moisture values will fluctuate.
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Page 21: Installation Of The Hydra Probe Into Soil
3.4.2 Installation of the Hydra Probe into Soil. The most critical thing about the installation of the Hydra Probe is the soil needs to be undisturbed and the base plate of the probe needs to be flush with the soil. To install the probe into the soil, first select the depth (see section 3.4.3 for depth selection). -
Page 22: Hydra Probe Depth Selection
3.4.3 Hydra Probe Depth Selection Like selecting a topographical location, selecting the sensor depth depends on the interest of the user. Farmers will be interested in the root zone depth while soil scientists may be interested in the soil horizons. Depending on the crop and the root zone depth, in agriculture two or three Hydra Probes may be installed in the root zone and one Hydra Probe may be installed beneath the root zone. - Page 23 retain water at field capacity longer than other soil horizons. Knowledge of the soil horizons in combination with the Hydra Probes accuracy will allow the user to construct a more complete picture of the movement of water in the soil. The horizons that exist near the surface can be 6 to 40 cm in thickness.
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Page 24: Back Filling The Hole After The Probes Are Installed
Figure 3.8 Illustration of soil horizons. In this frame, the soil horizons are very distinct and show the geological history of the soil. 3.4.4 Back Filling the Hole after the Probes are Installed. After soil is removed from the ground and piled up next to the hole, the horizons and soil become physically homogenized. - Page 25 If the soil is not trampled down while it is being back filled, the compaction and bulk density of the backfill will be considerably less than the native undisturbed soil around it. After a few months, the backfilled soil will begin to compact on its own and return to a steady state bulk density.
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Page 26: Measurements, Parameters, And Data Interpretation Analog Hydra Probe Output
4.1.4 ADC Reading 1 through 5 The ADC Reading 1 through 5 are the analog to digital values at 10 bits. They are the binary numbers that correspond to V1 through V5. They are used by Stevens for development or trouble shooting purposes. -
Page 27: Soil Temperature
reading, the diode temperature is usually very close, if not the same value as soil temperature. The diode temperature is used by the Hydra Probe to make algorithmic temperature correction to the electronics. Soil Temperature The user can select Fahrenheit or Celsius. Diurnal (daily) temperature fluctuations between daytime highs and nighttime lows may be observed with the Hydra Probe’s temperature data. -
Page 28: Soil Moisture Measurement Considerations
calculation can be much less straightforward, particularly when soil moisture is measured as a tension. 4.3.2 Soil Moisture Measurement Considerations Soil moisture measurements are important for a number of applications and for a number of different reasons. Some applications include; land slide studies, erosion, water shed studies, climate studies, predicting weather, flood warning, crop quality and yield optimization, irrigation, and soil remediation to name a few. -
Page 29: Soil Salinity (G/L Nacl)
Figure 4.1 soil textures and the available water Texture Clay Silty Clay Loam Sandy Loamy Sand Clay Loam Loam Sand Table 4.1 Maximum allowable depletions for different soil textures For example, let us suppose your soil is a sandy loam. From table 4.1, MAD = 0.5, From Figure 4.1 (or a soil surrey) PWP = 13% and the field capacity is 25%. -
Page 30: Soil Electrical Conductivity (Temperature Corrected)
Equation [4.4] is found in the literature (McBride 1994) and works well if the soil is not extremely acidic or extremely alkaline. To use the Soil Water Salinity calculation in equation [4.4], mix one part soil with one part water and take a reading with the Hydra Probe’s tines completely submerged in the water extract. -
Page 31: Theory Of Operation
The Hydra Probe is different from all other soil sensors because it measures both components of the complex dielectric permittivity of the soil. In other words, The Stevens Hydra Probe uses the reflected properties of a radio waves to measure soil moisture and soil electrical conductivity simultaneously. - Page 32 Where (E ) is imaginary dielectric permittivity, j = -1 and is the imaginary number, and (E ) is the real dielectric permittivity. Figure [5.1]. Illustration of polarization. The real dielectric permittivity of soil is mostly due to orientation polarization of water (Taken from Lee et al. 2003) The imaginary dielectric permittivity is directly related to the conductivity of the medium, the higher the imaginary dielectric permittivity, the higher the conductivity.
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Page 33: Real Dielectric And Imaginary Constants (Temperature Corrected)
The Hydra Probes’ design features such as the geometry of the wave guide and the frequency at 50 MHz allows the Hydra Probe to simultaneously measure both real and imaginary dielectric constants (Campbell, 1990). The algorithmic treatment method of the four raw voltages is derived from the solution to a complex function. -
Page 34: Solution Chemistry
Pathway 2 is the pathway that is attributed to the electrical conductivity of the soil water. Increasing the dissolved salts will increase the conductivity of pathway 2; however, like pathway 1, increases in the soil water content will increase the size of the pathway thus increasing the electrical conductivity. -
Page 35: Cation Exchange And Agriculture - Reclaiming Salt Infested Land
Agricultural soils over time may become sodic or saline and this may dramatically effect the health and yields of the crops. There are techniques that can remove the sodium to improve soil quality and increase crop production. The Stevens Hydra Probe can be an invaluable tool for monitoring the progress of saline soil reclamation. - Page 36 The outer portion of a soil particle at the molecular level is typically negatively charged. Positively charged sodium ions will bind or “hook” onto the surface of the soil micro particle. The opposite charges create an electronic attraction between the sodium ion and the soil. The sodium ions compete for negatively charged sites on the soil particle surface and in doing so, disperse the aggregates of soil.
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Page 37: Maintenance And Trouble Shooting
Maintenance and Trouble Shooting If a probe appears to be malfunctioning, there are generally three main reasons that may explain why a probe may appear to be malfunctioning. The three most common reasons why a probe may seam to be malfunctioning are: 1) Improper logger setup or improper wiring, 2) soil hydrology may produce some unexpected results, and 3) the probe is defective. -
Page 38: Check The Wiring
Stevens receives are not due to malfunctioning probes but rather an incorrect data logger setup. DOTSet is a Windows program used to program a Stevens DOT Logger. Please refer to Appendix C for more information about programming DOT Loggers. -
Page 39: Evapotranspiration
Figure 6.1 Measurement volume with a void space between the tine assembly. Void spaces between the tine assembly can also occur from changing soil conditions. Factors such as shrink/swell clays, tree roots or pebbles may introduce a void space. The following sections describe some of these and other factors. -
Page 40: Soil Bulk Density
6.4.3 Soil Bulk Density In general, the greater the soil density, the less water it will hold and the slower water will move through it. There will often times be soil horizons that will be more dense than others giving the soil different hydrological properties with depth. -
Page 41: Bioturbation
6.4.6 Bioturbation Organisms such as plants and burrowing animals can homogenize soil and dislodge soil probes. A tree root can grow between the tines affecting the measurements and in some cases, tree roots can bring a buried soil probe to the soil surface. Burrowing mammals and invertebrates may decide that the Hydra Probes’... - Page 42 thus as the wetting front move down into the soil, the regions between the peds will be the preferential water pathway. As the wetting font moves through the soil column the soil moisture measurements may be temporarily biased by the peds. For example, if the soil probe’s measurement volume is residing entirely in a single ped, the probe would not detect the wetting front until the water infiltrates the ped.
- Page 43 Appendix A - SDI-12 Communication SDI-12 (serial data interface at 1200 baud) communications protocol allows compatible devices to communicate with each other. More information about SDI-12 can be found at http://www.sdi-12.org/. SDI-12 Wiring Information The SDI-12 Hydra Probe has three wires. A ground wire, a +12 volt power wire and a blue data wire.
- Page 44 Stevens Hydra Probe SDI-12 Command Specification For Firmware Versions 2.7 and Later The Stevens HP2 is fully compliant with the SDI-12 Version 1.2 command specification. As such, responses to many of the standard commands are not detailed here. A complete description of the SDI-12 Command Grammar is contained in the SDI-12 Protocol Specification.
- Page 45 The following measurement set descriptions detail the parameters returned by each of the measurement commands. For the aM! command, only the default reading set is listed. All data transmitted using SDI-12 must be printable ASCII characters. The first character of any command or response is the address.
- Page 46 <constant> Single ASCII character specifying the water constant accessed by the command. Water constants are used in conjunction with the Custom soil types. When a Custom soil type is selected, the probe will use the water constants to compute the soil moisture content. Custom 1 uses all 4 constants, Custom 2 uses the first 2 constants only.
- Page 47 Response: aFGHOJ<CR><LF> aXM=3! – Set default measurement set to measurement set 3 Sets the default measurement set to KLMNOPQ. Response: aKLMNOPQ<CR><LF> aXM=4! – Set default measurement set to measurement set 4 Sets the default measurement set to ABCDE. Response: aABCDE<CR><LF> aXM=5! –...
- Page 48 Data Signal B inverting signal Baud Rate 9600 8N1 Power Consumption <10 mA Idle 30 mA Active Table 2.3 Digital RS-485 Hydra Probe II Information. Stevens Hydra Probe RS-485 Command Specification For Use with Firmware Version 2.7 and Later Command Format AAACC<CR><LF> Execute AAACC=?<CR><LF>...
- Page 49 <quick>: Quick mode, 1 character {‘1’ – ‘6’, ‘X’} <warmup>: Warmup time, 1-5 digits, 0-65535 <bool>: Boolean value, 1 character, {‘0’ | ‘1’} <firmware>: Firmware, 3 or 4 bytes, formatted like “2.7” or “R2.7” or “2s7” <text>: Printable ASCII text <float>: Decimal number, optionally using a form of scientific notation.
- Page 50 Soil Type Description: Gets/sets the probe soil type. Access Level: Read/Write Read Addresses: Broadcast, Exact <addr>ST=?<CR><LF> Read Command: Read Response: <addr><CR><LF> Write Addresses: Broadcast, Exact, Wildcard Write Command: <addr>ST=<soil><CR><LF> Write Response: (No response for wildcard address) <addr><soil><CR><LF>...
- Page 51 Advanced Configuration Commands Location Description: Gets/sets the probe location. Access Level: Read/Write Read Addresses: Broadcast, Exact Read Command: <addr>LO=?<CR><LF> Read Response: <addr><text><CR><LF> Write Addresses: Exact <addr>LO=<text><CR><LF> Write Command: Write Response: <addr><text><CR><LF> Description Description: Gets/sets the probe description. Access Level: Read/Write Read Addresses: Broadcast, Exact Read Command: <addr>DS=?<CR><LF>...
- Page 52 Debug Commands Warmup Time Description: Gets/sets the custom probe warmup time. Access Level: Read/Write Read Addresses: Broadcast, Exact Read Command: <addr>WT=?<CR><LF> Read Response: <addr><warmup><CR><LF> Write Addresses: Exact Write Command: <addr>WT=<warmup><CR><LF> <addr><warmup><CR><LF> Write Response: Probe Enable Description: Gets/sets whether the probe circuitry is enabled. Access Level: Read/Write Read Addresses: Broadcast, Exact Read Command:...
- Page 53 RS-485 TRANSMIT SETS (tc) indicates values that have been temperature corrected T0 - Transmit Set 0: H) Moisture J) Soil Electrical Conductivity (tc) F) Temp C G) Temp F O) Soil Electrical Conductivity K) Real Dielectric Permittivity M) Imag Dielectric Permittivity L) Real Dielectric Permittivity (tc) N) Imag Dielectric Permittivity (tc) T1 - Transmit Set 1:...
- Page 54 Appendix C - Stevens DOT Logger with the SDI-12 Hydra Probe The Stevens DOT Logger is the perfect companion for the Hydra Probe. The DOT logger has 100 SDI-12 channels for recording data. For example, 33 Hydra Probes each measuring 3 parameters such as EC, temperature and soil moisture, can be connected to a single DOT logger.
- Page 55 Enter Sensor Command: 0a1! Response from sensor: 1! If in doubt, type ?! to verify the address change. F) While in Transparent Mode, the user may wish to confirm the parameter set. Type 1XM! The response should be: Enter Sensor Command: 1XM! Response from sensor: 1HJFGOKMLN This means that a probe with an address of 1 is set for the default parameter set.
- Page 56 Steps 1 though 5 set up the data logger and the probes. Once logging is enabled, the system will start taking measurements and start logging data. Step 6 Retrieving Data. To retrieve the data, launch “Stevens Logger XL”. Step 7 Set up Logger XL. From the main window select “Define DOT logger batch”.
- Page 57 Select “All channels” in the Batch list Dialog box. Next, go to the configuration menu, data access setting and: check “auto create data.csv.file” check “append data to file”. Under configurations, comport settings: select COM1, Echo off, Parity none, Stop bits 1, Data bits 8 Flow control Xon/Xoff.
- Page 58 Appendix D - Statistics All measurements, no matter how careful and scientific, are subject to some uncertainties. Statistics is the branch of mathematics that can quantify uncertainties. The Hydra Probe’s design and signal processing reduces error to a magnitude that has little impact on hydrological measurements such as permanent wilting point, field capacity and saturation.
- Page 59 Statistical Definitions Shows how well a distribution of points fit on a straight line. The closer the R value is to 1 the more correlated the data the better the accuracy. In the above definition, The average The Standard deviation represents precision and reproducibility. Precision verses accuracy Figure A.4.1 Good Precision Figure A.4.2 Good Accuracy...
- Page 60 Appendix E - Ordering Information Table E.1 lists the part numbers, and some accessories such as the Stevens Dot Logger. The RS- 485 Hydra Probe has a cable length limit of 1000 meters. The SDI-12 version has a limit of 50 meters, and the analog versions have a maximum cable length of 33 meters.
- Page 61 Appendix F - Useful links Stevens Water Monitoring Systems, Inc. www.stevenswater.com The Soil Science Society of America http://www.soils.org/ The US Department of Agriculture NRCS Soil Climate Analyses Network (SCAN) http://www.wcc.nrcs.usda.gov/scan/ The US Department of Agriculture NRCS Snotel Network http://www.wcc.nrcs.usda.gov/snow/ The US Geological Survey Agricultural Weather Network (AgriMet) http://www.usbr.gov/pn/agrimet/...
- Page 62 Appendix G - References Blonquist, J. M., Jr., S. B. Jones, D.A. Robinson,. Standardizing Charaterization of Electromagnetic Water Content Sensors: Part 2. Evaluation of Seven Sensing Systems. Vadose Zone J. 4:1059-1069 (2005) Birkeland, P. W. Soils and Geomorphology 3 Ed. Oxford University Press 1999 Campbell, J.
- Page 63 This warranty covers all defects which you bring to the attention of Stevens within two years from the date of shipment. If your Stevens product is defective, Stevens will repair or replace it and will ship it back to you free of charge.
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