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TABLE OF CONTENTS
2.1 Installation ................................................................................................ 2
2.1.1 Preparation ...................................................................................... 2
2.1.2 Installation Angle ............................................................................. 3
2.1.3 Installation Depth ............................................................................ 3
2.1.4 Test Connection ............................................................................... 6
2.1.5 Installation Methods ........................................................................ 6
2.2 Connecting ................................................................................................. 9
2.2.1 Adding a Custom Shaft Extension .................................................... 9
2.2.2 Connect to METER Logger .............................................................. 10
2.2.3 Connect to Non-METER Logger ...................................................... 10
2.3 Communication ....................................................................................... 11
....................................................................................................... 13
3.1 Specifications .......................................................................................... 13
3.2 Components ............................................................................................ 16
3.3 Theory ...................................................................................................... 17
3.3.1 Water Potential Measurement ....................................................... 17
3.3.2 Measurement Range ...................................................................... 18
3.3.3 Measurement Accuracy ................................................................. 18
3.3.4 Temperature Measurement ............................................................ 19
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18551-00
11.2023
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Summary of Contents for METER TEROS 22
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Page 1: Table Of Contents
2.1.4 Test Connection ................6 2.1.5 Installation Methods ................ 6 2.2 Connecting ....................9 2.2.1 Adding a Custom Shaft Extension ............ 9 2.2.2 Connect to METER Logger .............. 10 2.2.3 Connect to Non-METER Logger ............10 2.3 Communication ..................11 3. System ....................... - Page 2 3.4 Considerations..................19 3.4.1 Measuring in Frozen Soils .............. 19 3.4.2 Measuring in High Salinity ............. 20 3.4.3 Temperature Sensitivity ..............20 4. Service ....................... 22 4.1 Calibration ....................22 4.2 Maintenance .................... 22 4.3 Troubleshooting ..................23 4.4 Customer Support..................23 4.5 Terms and Conditions ................
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Page 4: Introduction
INTRODuCTION 1. INTRODuCTION Thank you for purchasing the TEROS 22 Soil Water Potential Sensor from METER Group. Prior to use, verify the TEROS 22 arrived in good condition. The TEROS 22 is designed to be a maintenance-free matric potential sensor for long-term, continuous field measurements. The TEROS 22 measures the dielectric permittivity of a solid matrix to determine the water content of the solid matrix. -
Page 5: Operation
PRECAuTIONS METER sensors are built to the highest standards, but misuse, improper protection, or improper installation may damage the sensor and possibly void the manufacturer’s warranty. Before integrating TEROS 22 into a system, make sure to follow the recommended installation instructions and have the proper protections in place to safeguard sensors from damage. -
Page 6: Installation Angle
OPERATION 2.1.2 INSTALLATION ANGLE The TEROS 22 should be installed at an angle ( ) of 0° to 80° from horizontal (Figure 1). An angled installation position does not disturb typical water flow and reduces the chances of preferential water flow along the shaft. - Page 7 TEROS 22 Because the TEROS 22 should be installed at an angle from horizontal ( ), installation depth is not equal to drilling depth (Figure 3). To calculate the correct drilling depth, use Equation 1 or Table 1. installation depth drilling depth = Equation 1 sinα...
- Page 8 OPERATION Table 1 Drilling depth in centimeters for installation depths and angles Installation Angle 80° 75° 70° 65° 60° 55° 50° 45° 40° 35° 30° 25° 20° 15° 10° 116 173 117 155 100 118 146 193 105 120 142 175 109 122 140 166 205 104 113 124 139 160 189 104 110 117 127 140 157 180 213...
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Page 9: Test Connection
Customer Support. 2.1.5.1 METHOD 1: PILOT HOLE METER recommends drilling an appropriately sized pilot hole with a masonry drill bit for shallow installations (less than 120 cm) to the required depth (Figure 4). Advantages • Minimizes the soil disturbance •... - Page 10 OPERATION Figure 4 Pilot hole installation depths Figure 5 Drill bit and level...
- Page 11 This method is recommended if the sensor end and cables should not be exposed at the soil surface. After digging a trench, METER recommends using a masonry drill to drill an appropriately sized pilot hole (Section 2.1.3). Installing into a trench wall may be easier than drilling the whole depth from the soil surface.
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Page 12: Connecting
2.2.1 ADDING A CuSTOM SHAFT EXTENSION The TEROS 22 comes standard with three optional shaft lengths of 40, 80, and 120 cm (15.7, 31.5, and 47.3 in), but it can be ordered without the standard shaft extensions if a custom length is needed. -
Page 13: Connect To Meter Logger
METER data loggers record the TEROS 22 measurements every minute and return the minute-average data across the chosen measurement interval. TEROS 22 data can be downloaded from METER data loggers using either ZENTRA Utility or ZENTRA Cloud. Refer to the logger user manual for more information about these programs. -
Page 14: Communication
NOTE: The acceptable range of excitation voltages is from 4.0 to 15 VDC. If the TEROS 22 cable has a standard stereo plug connector and needs to be connected to a non-METER data logger, use one of the following two options. Option 1 Clip off the stereo plug connector on the sensor cable. - Page 15 Detailed information can also be found in the application note Setting SDI-12 addresses on METER digital sensors using Campbell Scientific data loggers and LoggerNet. When using the sensor as part of an SDI-12 bus, excite the sensors continuously to avoid...
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Page 16: System
±1 °C COMMuNICATION SPECIFICATIONS Output DDI Serial or SDI-12 communications protocol Data Logger Compatibility METER ZL6 and EM60 data loggers or any data acquisition system capable of 4.0- to 15-VDC power and serial or SDI-12 communication PHySICAL SPECIFICATIONS Dimensions Diameter 1.7 cm (0.67 in) - Page 17 TEROS 22 Sensor Diameter 1.7 cm (0.67 in) Operating Temperature Range Minimum –40 °C Typical Maximum +60 °C NOTE: Sensors may be used at higher temperatures under certain conditions; contact Customer Support for assistance. Cable Length 5 m (standard) 75 m (maximum custom cable length) NOTE: Contact Customer Support if a nonstandard cable length is needed.
- Page 18 SySTEM Digital Input Voltage (logic low) Minimum –0.3 V Typical 0.0 V Maximum 0.8 V Power Line Slew Rate Minimum 1.0 V/ms Typical Maximum Current Drain (during measurement) Minimum 3.0 mA Typical 5.0 mA Maximum 16.0 mA Current Drain (while asleep) Minimum Typical 0.03 mA...
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Page 19: Components
TEROS 22 Measurement Duration Minimum 175 ms Typical Maximum 200 ms COMPLIANCE EM ISO/IEC 17050:2010 (CE Mark) EN 55011:2016 / A1:2017 (RCM Mark) 3.2 COMPONENTS The TEROS 22 sensor measures the water potential and temperature of soil with porous ceramic discs (Figure 10). TEROS 22 sensors measure moisture content changes of two engineered ceramic discs sandwiched between stainless steel screens and the circuit board. -
Page 20: Theory
SySTEM 3.3 THEORy TEROS 22 sensors measure water potential, so they are not as sensitive to soil disturbance as water content sensors. TEROS 22 requires good hydraulic contact with the surrounding soil for accurate measurements. 3.3.1 WATER POTENTIAL MEASuREMENT All soil water potential measurement techniques measure the potential energy of water in equilibrium with water in the soil. -
Page 21: Measurement Range
METER designed the ceramic discs to approach this ideal. The discs have a total pore volume that is weighted toward the larger pores, which drain at water potentials within the plant-available range (approximately −33 to −2,000 kPa). -
Page 22: Temperature Measurement
Do not install the sensor with the black body above ground. The shaft extension piece on the TEROS 22 are white to minimize potentiaing heating and can be installed with some of the extention piece aove ground. However, any part of the shaft extension exposed above ground should be protected from damand and insulating the shaft will help minimize impacts on temperature measurements. -
Page 23: Measuring In High Salinity
TEROS 22 TEROS 22 does not accurately measure water potential in frozen soil conditions. However, the water potential of the soil under frozen soil conditions can be estimated by measuring the soil temperature accurately (Koopmans and Miller, 1966). For each 1 °C decrease in temperature below 0 °C, the water potential in the soil decreases by ~1,200 kPa. - Page 24 SySTEM −200.0 Sensor 1 (5-cm depth) Sensor 2 (15-cm depth) −400.0 −600.0 −800.0 −1,000.0 −1,200.0 −1,400.0 −1,600.0 −1,800.0 Figure 12 Temperature sensitivity data for TEROS 22 sensors...
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Page 25: Service
Measurements as the soil wets up are slightly drier (more negative water potential) than the true water potential of the soil. METER wetting and drying tests show the magnitude of the hysteresis error is <10 kPa in the −20 to −100 kPa range. -
Page 26: Troubleshooting
Table 2 Troubleshooting TEROS 22 Problem Possible Solutions Data logger is not If using a METER logger, update logger firmware. recognizing sensor Check to make sure the connections to the data logger are both correct and secure. Ensure that your data logger batteries are not dead or weakened. -
Page 27: Terms And Conditions
NOTE: For products purchased through a distributor, please contact the distributor directly for assistance. 4.5 TERMS AND CONDITIONS By using METER instruments and documentation, you agree to abide by the METER Group, Inc. Terms and Conditions. Please refer to metergroup.com/terms-conditions... -
Page 28: References
REFERENCES REFERENCES Bittelli, Marco, and Markus Flury. 2009. “Errors in Water Retention Curves Determined with Pressure Plates.” Soil Science Society of America Journal 73 (5): 1453–60. https://doi.org/10.2136/sssaj2008.0082Citations: 124. Campbell, Gaylon S. 1988. “Soil Water Potential Measurement: An Overview.” Irrigation Science 9: 265–73. https://doi.org/10.1007/BF00296702. Frydman, Samuel, and Rafi Baker. -
Page 29: Index
TEROS 22 INDEX maintenance 22 cable colors 10 matric potential 17, 20 calibration 18, 22 moisture characteristic curve 18–19 ceramic pore size 19–20 cleaning. See maintenance components phone number 23, 24 ceramic discs 16, 17, 18–19, 22, 22–23, 23 circuit board 16 screens 16, 22 references 25 sensor body 16, 19...
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