栽培介質水分量測 v1.0

1. 栽培介質水分量測 v1.0 方煒 台大生機系教授 2005/11/3

2. 栽培介質含水率表示方式 • 體積法：m3/m3 • 重量法：g/g • 乾基 (水重/乾土塊重) • 濕基(水重/(水+乾土塊重))。

3. 土壤含水率量測方式 • 蒸發盤 • 張力計 • 電阻(石膏)塊 • 電容片 • 熱分散法 • 時域反射法 • 中子熱化法 • 重量變化 （荷重元）

4. 目前最熱門的產品 ECH2O Probe

5. ECHO Probes: Models and Specifications ECHO probe model EC-20 (20cm length) ECHO probe model EC-10 (10cm length)

8. The ECH2O System

9. ECH2O Data Loggers Model Em50 • The Em50 is the non-radio enabled data collection system. It interfaces with up to five inputs, and uses an RS-232 cable connected to the comm port in order to set the station id, time, date, scan interval, and to collect data. Model Em50R • The Em50R system has an added radio transceiver module, which you can use to set the station id, time, date, scan interval, and to collect data via telemetry. One Rm1 can collect data from different EM50Rs. The radio module has 900MHz, 916MHz or 2.4GHz spread spectrum RF communication (depending on individual country regulations)and a 5-mile line of sight range under most conditions.

10. ECH2O DataTrac Mobile • ECH2O DataTrac Mobile • *Data Shuttle • *Program Ech2O Dataloggers • *Scan Datalogger Sensor Ports DataTrac Mobile runs on Windows CE Pocket PCs. Using DataTrac Mobile, you can program Ech2o Loggers and download data for transport to your PC. While connected to the logger you can also scan the ports for current sensor readings.Simply connect the Pocket PC serial cable to the Ech2o Serial Cable Adapter and plug the 3.5 mm connector into "Comm Port." Launch the program and press connect.

11. ECH2O Data Receivers • The DataStation is an always on radio base station that allows you to remotely collect and store data from multiple Em5R data loggers. The Data Station, being always on, receives and saves data from Em5R loggers operating in transmit mode. Data can then be downloaded directly from the Data Station to your computer at your convenience. DataStation data can be graphed and analyzed using ECH2O DataTrac software. • Features:• External antenna connector• RS232 serial cable connectivity• Storage for over 36,000 broadcast packets• Flexible 9-24V AC/DC power• Battery-backed solar power (coming soon)

12. ECH2O Data Receivers • The Rm1 is a radio modem for communication with the ECH2O Logger. The Rm1 can be used to query the ECH2O Logger or as a data relay for extending the range of radio telemetry between the logger and DataStation. • Specifications:• Radio Frequency: Type: 902-928 Mhz/2.4 Ghz.• Serial Data Interface: RS-232• Range: 1 to 10 km, varies depending on line of sight, interference, and antenna options• Supply Voltage: 7-18VDC (AC Adapter supplied)• Current Consumption: 70-210mA• Dimensions: 7.9cm x 13.9cm x 3.8• Weight: 6.9 oz. (195.6g)• Operating Environment: 0 - 70 °C, 10-90% RH

14. The ECH2O Dielectric Aquameter • is a new, low-cost sensor for measuring volumetric water content of soil and other porous materials. It uses new technology and durable materials to enable you to monitor moisture content over a wide geographic area. Best of all, it is inexpensive enough to allow you to install several of them in your field or plot without breaking the bank.

15. The ECH2O probe • measures the dielectric constant of the soil in order to find its volumetric water content. It does this by finding the rate of change of voltage applied to the sensor once it is buried in the soil. There are other probes that measure water content this way, but the ECH2O probe is the only one of its kind to have a comparatively low sensitivity to saline and temperature effects in the soil. Furthermore, it has a very low power requirement, which makes long-term monitoring more cost-effective. And its extremely high resolution makes it possible to accurately monitor water use daily or even hourly.

16. Applications • The ECH2O probe's versatility allows it to be used in a variety of applications, including: • Irrigation scheduling and management • Water balance studies • Vadose zone monitoring • Landfill and hazardous waste site monitoring • Monitoring land-applied waste water

17. Specifications Range: 0 to saturation, volumetric water content Measurement time: 10ms Accuracy:±3% typical± 1% with soil-specific calibration Resolution: 0.002m3/m3 Output Range:Dry soil: 375 to 1000mVAir: 255 to 260mV Power: Requirements: 2VDC @ 3mA to 5VDC @ 7mAOutput: 10-40% of excitation voltage (250-1000mV at 2500mV excitation)

19. precipitation gauge Self-emptying Tipping-bucket precipitation gauge for use with Em5 loggers

20. The rain is collected by the funnel and runs into a self-emptying spoon, which automatically tips and is emptied when it is reaches a volume of one millimeter of water. Each time the spoon empties, a measurement is sent and recorded by the Em5. • You can connect up to 122m (400 feet) of extension cables from the Rain Gage to an Em5 or other logger before experiencing any signal loss

21. ECH2O DataTrac(Graphing Software)

22. Accessories The Em5 is a convenient, high-quality data collection system designed for use with the ECHO probes. The EM5 is a 5-channel, self-contained data recorder with an optional radio telemetry module (model Em5R). Its low power consumption gives you the ability to make as many measurements as you want (even hourly) over a long period of time (several months), with minimal battery usage.

23. Accessories

24. Accessories ECHO Check is designed for use with your ECHO probes for a quick measurement of water content. Simply connect the ECHO probe to the ECHO Check, and with the press of a button, you get an instant measurement of Volumetric Water content.

25. Accessories • With lightweight (140g) ECHO Check hand-held readout, you can make rapid measurements of your installed ECHO probes. Simply plug in the ECHO probe's 3.5 mm connector and press the left button of the ECHO check to get an instant reading of water content. You can also to calibrate the ECHO check for the specific soil type you are measuring. • Readings are displayed in units of volumetric water content (m3/m3), inches per foot (in/ft), or millivolt output.

26. 栽培介質水分含量量測原理-1 • Any sensor which accurately measures permittivity can be used to determine volumetric water content. Confounding factors typically are temperature and salinity. • Water has a permittivity of about 80, while the value for soil minerals is around 4, and air is 1. This high value for water results in relatively large changes in the permittivity of soil when the water content changes.

27. 栽培介質水分含量量測原理-2 • Dielectric moisture sensors, or aquameters, are of two types. One measures the dielectric constant of a medium by finding the time taken for an electromagnetic pulse to traverse a transmission line buried in the medium. This type of sensor is called a time domain reflectometer (TDR) sensor. • The second type of sensor measures the dielectric constant of a medium by finding the rate of change of voltage on a sensor that is embedded in the medium. This type of sensor is called capacitor type sensor. • TDR type sensor is normally expensive and relatively complex. Capacitor type sensor is relatively cheap and simple.

28. What is Permittivity ? • The permittivity of a medium is an intensive physical quantity that describes how an electric field affects and is affected by the medium. • Permittivity can be looked at as the quality of a material that allows it to store electrical charge. A given amount of material with high permittivity can store more charge than a material with lower permittivity.

29. What is dielectric constant ? • The dielectric constantεris defined as the ratio: εr= εs / εo = εs /( 8.85 x 10-12 F/m) = εs x 1.13 x 1011 • Where εs: the static permittivity of the material in question, ε0: the vacuum permittivity. This permittivity of free space is derived from Maxwell's equations and is equals theratio D/E in vacuum, whereDis the electric flux densityandEis theelectric field intensity. • In vacuum (free space), the permittivity εs is just ε0, so the dielectric constant is unity.

30. Dielectric constant of some materials at room temperature

31. FAQ • http://www.decagon.com/echo/faq.html More literature to download • http://www.decagon.com/instruments/agdownload.html

32. Accessories Long-term water flux meter for monitoring downward water movement through the soil. Used with the Em5 and Em5R loggers. Now you can measure how much water leaches from your root zone using drain gauge.

33. Accessories • for use with the Em5 and Em5R loggers. • If you are using the ECHOTemp sensor in air, we strongly recommend that you use it in a radiation shield. The best type for this kind of sensor is the one available from Davis Instruments, Model 7714 (picture below).

34. Dielectric Leaf Wetness • The Dielectric Leaf Wetness Sensor, like its name implies, measures surface wetness by measuring changes in the dielectric on the sensor surface. Designed to mimic the thermodynamic properties of a leaf in shape and dimensions. Specifications are in development.