Related Manuals for Decagon Devices MPS-2
Summary of Contents for Decagon Devices MPS-2
- Page 1 MPS-2 & MPS-6 Dielectric Water Potential Sensors Operator’s Manual Decagon Devices, Inc. Version: December 1, 2014 — 14:32:49...
- Page 2 MPS-2 & MPS-6 Decagon Devices, Inc. 2365 NE Hopkins Court Pullman WA 99163 Phone: 509-332-5600 Fax: 509-332-5158 Website: www.decagon.com Email: support@decagon.com or sales@decagon.com Trademarks c 2011-2014 Decagon Devices, Inc. All Rights Reserved...
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Page 3: Table Of Contents
6 Maintenance and Troubleshooting 6.1 MPS-2 & MPS-6 in Frozen Soils ... . 22 6.2 Troubleshooting ..... . 23... -
Page 4: Introduction
1 INTRODUCTION Introduction Thank you for choosing the Dielectric Water Potential Sensor, model MPS-2 or MPS-6, for measuring soil water potential and tempera- ture. This manual helps you to understand the sensor features and how to use it successfully. Note: The engineering community commonly uses the term soil suc- tion instead of soil water potential. -
Page 5: Specifications
1 INTRODUCTION MPS-2 & MPS-6 Specifications Water Potential Range: 9 to 100,000 kPa (pF 1.96 to pF 6.01) Resolution: 0.1 kPa Accuracy: MPS-6: (10% of reading + 2 kPa) from 9 to 100 kPa MPS-2: (25% of reading + 2 kPa) from... -
Page 6: Warranty Information
MPS-2 & MPS-6 1 INTRODUCTION Connector Types: 3.5 mm (stereo) plug or stripped & tinned lead wires (3) Cable Length: 5 m standard; custom lengths available upon request Data Logger Compatibility (not exclusive): Decagon: Em50, Em50R, Em50G (rev 2.13+) Campbell Scientific: Any logger with serial I/O including CR10X, CR23X, any CRBasic type logger (CR850, 1000, 3000, etc.) - Page 7 1 INTRODUCTION MPS-2 & MPS-6 occasioned by or arising out of the installation, operation, use, mis- use, nonuse, repair, or replacement of said material and equipment, or out of the use of any method or process for which the same may be employed.
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Page 8: About The Mps-2 & Mps-6
The only functional difference between the MPS-2 and MPS-6 is the amount of effort spent calibrating the sensor. Each MPS-2 has a two point calibration that results in a fair degree of accuracy, while the MPS-6 has a six point calibration that results in research-grade accuracy. -
Page 9: Theory
3 THEORY MPS-2 & MPS-6 Theory Water Potential Measurement There are two basic parameters that describe the state of water in soil: one is soil water content, or the amount of water per unit of soil, and the other is soil water potential, or the energy state of water in the soil. -
Page 10: Temperature Measurement
Water content and water potential are related by a relationship unique to a given material, called the moisture characteristic curve. The ceramic used with the MPS-2 and MPS-6 has a wide pore size distribution and is consistent between discs, giving each disc the same moisture characteristic curve. - Page 11 3 THEORY MPS-2 & MPS-6 in C unless otherwise stated in your preferences file in either the DataTrac 3 or ECH2O Utility programs. If the black plastic over- mold of the sensor is in direct sunshine, the temperature measure- ment may read high. Exposure of the overmold to solar radiation also drastically decreases the life expectancy of the sensor.
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Page 12: Range And Accuracy
4 RANGE AND ACCURACY Range and Accuracy Measurement Range The MPS-2 and MPS-6 measure the water content of porous ceramic discs and convert the measured water content to water potential us- ing the moisture characteristic curve of the ceramic.(See Section 3) It is important for sensor function that the ceramic drains over a wide water potential range.(See Figure 2) The size of the pore determines... -
Page 13: Measurement Accuracy
The MPS-2 and MPS-6 sensors are identical in construction, with the only difference between the two sensor types being the calibra- tion method applied. We calibrate the MPS-2 and MPS-6 at a vac- uum saturated state (0 kPa), and at an air-dry state ( 100,000 kPa). - Page 14 9 to 100 kPa. Dry end At water potentials drier than 100 kPa, both the MPS-2 and MPS-6 rely on the linear relationship between water content and the loga- rithm of water potential that is a fundamental characteristic of soils and the MPS-2 or MPS-6 ceramic disc.
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Page 15: Calibration
Calibration Wet End We calibrate each MPS-2 and MPS-6 sensor at an air-dry and vac- uum saturated state at Decagon Devices. This two-point calibration results in the accuracy stated above. Although better wet-end accu- racy can be achieved through user calibration of the MPS-2 sensor, it is more cost-effective and convenient to simply order MPS-6 sensors... -
Page 16: Soil Type Dependence
4 RANGE AND ACCURACY Dry End As described in the section above, both the MPS-2 and MPS-6 rely the linear relationship between water content and the logarithm of water potential for calibration in the dry end. Lab testing and field evaluations have shown that additional calibrations in this region are not necessary, but could improve accuracy some. - Page 17 4 RANGE AND ACCURACY MPS-2 & MPS-6 most accurate as the soil dries. Measurements as the soil wets up are slightly drier (more negative water potential) than the true water potential of the soil. Our wetting and drying tests show the mag-...
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Page 18: Connecting To A Logger
Connecting to Em50/Em50R/Em50G logger The MPS-2 and MPS-6 work best with the Em50 data logger se- ries. Simply plug the 3.5 mm “stereo plug” connector directly into one of the five sensor ports. Next, configure your logger port for... -
Page 19: Connecting To A Non-Decagon Logger
Figure 5: 3.5 mm Stereo Plug Wiring Connecting to a Non-Decagon Logger You may purchase the MPS-2 and MPS-6 sensors for use with non- Decagon data loggers. These sensors typically come pre-configured with stripped and tinned (pigtail) lead wires for use with screw termi- nals. - Page 20 Figure 7: Wire Illustration Note: The acceptable range of excitation voltages is from 3.6 to 15 VDC. If you wish to read the MPS-2 or the MPS-6 with the Campbell Scientific Data Loggers, you need to power the sensors off of the 5 V, 12 V, or switched 12 V port.
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Page 21: Using Non-Decagon Loggers
SDI-12 for communication. If you plan on using SDI-12 for com- munication with the sensor, please see our Integrator’s guide un- der the support tab on the MPS-2 and MPS-6 product pages at http://www.decagon.com. There are several benefits and drawbacks regarding the SDI-12 pro-... - Page 22 Address The SDI-12 protocol requires that all sensors have a unique address. MPS-2 and MPS-6 sensors come from the factory with an SDI-12 ad- dress of 0. To add more than one SDI-12 sensor to a bus, the sensor address must be changed. Address options include 0...9, A...Z, a...z.
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Page 23: Installing The Sensors
Because the MPS-2 and MPS-6 measure water potential, they are not as sensitive to air gaps or soil disturbance as water content sen- sors. The MPS-2 and MPS-6 need good hydraulic contact with the surrounding soil. The preferred method for installing the sensor is to... -
Page 24: Campbell Scientific Programs
MPS-2 & MPS-6 5 CONNECTING TO A LOGGER Campbell Scientific Programs Because the sensors use digital rather than analog communication, they require special considerations when connecting to a Campbell Scientific data logger. Please visit our website at http://www.decagon .com/support to view sample Campbell Scientific programs. -
Page 25: Maintenance And Troubleshooting
5 at the frequency of the sensor measurement meaning that the MPS-2 or MPS-6 can no longer accurately measure the water in the ceramic. The MPS-2 and MPS-6 do not accurately measure the water potential of soil in frozen soil conditions. How-... -
Page 26: Troubleshooting
2. Ensure that your data logger batteries are not dead or weak- ened. 3. Check the configuration of your data logger in ECH2O Utility or DataTrac 3 to make sure you have selected MPS-2 or MPS-6. 4. Ensure that you are using the most up to date software and firmware. - Page 27 6 MAINTENANCE AND TROUBLE MPS-2 & MPS-6 3. Check the ceramic disc for damage or contamination.
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Page 28: References
MPS-2 & MPS-6 7 REFERENCES References Bittelli, M. And M. Flury, 2009. Errors in Water Retention Curves Determined with Pressure Plates. Soil Science Society of America Journal 73: 1453-1460 Campbell, G. S., 1988. Soil water potential measurement: an overview. Irrigation Science 9:265-273. -
Page 29: Declaration Of Conformity
MPS-2 & MPS-6 Year of First Manufacture: 2011 This is to certify that the MPS-2 and MPS-6 dielectric water poten- tial sensors, manufactured by Decagon Devices, Inc., a corporation based in Pullman, Washington, USA meet or exceeds the standards for CE compliance as per the the aforementioned Council Directives. - Page 30 Index Accuracy, 2, 9 Wet End, 10 Model Number, 26 Calibration Moisture Characteristic Curve, 7 Dry End, 13 Wet End, 12 Range, 9 CE Compliance, 26 References, 25 Ceramic Disc, Handling, 22 Sandy Soil, 20 Ceramic Discs, 7 Sensor, Installation, 20 Communication Soil Water Content, 6 Address, 19...
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