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Campbell 229 Instruction Manual

Heat dissipation matric water potential sensor
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229 Heat Dissipation Matric
Water Potential Sensor
Revision: 5/09
C o p y r i g h t
©
2 0 0 6 - 2 0 0 9
C a m p b e l l
S c i e n t i f i c ,
I n c .

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Summary of Contents for Campbell 229

  • Page 1 229 Heat Dissipation Matric Water Potential Sensor Revision: 5/09 C o p y r i g h t © 2 0 0 6 - 2 0 0 9 C a m p b e l l S c i e n t i f i c , I n c .
  • Page 2 Warranty and Assistance The 229 HEAT DISSIPATION MATRIC WATER POTENTIAL SENSOR is warranted by CAMPBELL SCIENTIFIC, INC. to be free from defects in materials and workmanship under normal use and service for twelve (12) months from date of shipment unless specified otherwise. Batteries have no warranty.

  • Page 3: Table Of Contents

    229 Sensor Table of Contents PDF viewers note: These page numbers refer to the printed version of this document. Use the Adobe Acrobat® bookmarks tab for links to specific sections. 1. General Description.............1 1.1 Compatibility ....................2 1.2 Measurement Principle ................2 2.
  • Page 4 229 Sensor Table of Contents 9. References..............28 List of Figures 1-1. 229 Heat Dissipation Matric Water Potential Sensor and Hypodermic Assembly ..................... 1 1-2. CE4 and CE8 Current Excitation Modules..........2 1-3. Typical Temperature Response of 229 Sensor in Silt Loam Soil ... 3 4-1.

  • Page 5: General Description

    229 Heat Dissipation Matric Water Potential Sensor 1. General Description The 229 Heat Dissipation Matric Water Potential Sensor uses a heat dissipation method to indirectly measure soil water matric potential. The active part of the 229 Soil Water Potential Sensor is a cylindrically-shaped porous ceramic body. A heating element which has the same length as the ceramic body is positioned at the center of the cylinder.

  • Page 6: Compatibility

    229 Heat Dissipation Matric Water Potential Sensor Use of the 229 sensor requires a constant current source. Campbell Scientific offers the CE4 and CE8 current excitation modules (Figure 1-2), which have respectively four and eight regulated outputs of 50 milliamp ±0.25 milliamp.

  • Page 7: Typical Temperature Response Of 229 Sensor In Silt Loam Soil

    229 Heat Dissipation Matric Water Potential Sensor A change in the water potential and water content of the ceramic matr ix causes a corresponding change in the thermal conductivity of the ceramic/water complex. As the water content in the ceramic increases, the thermal conductivity of the complex also increases.

  • Page 8: Specifications

    229 Heat Dissipation Matric Water Potential Sensor 2. Specifications Measurement range: -10 to -2500 kPa Measurement time: 30 seconds typical hermocouple type: copper / constantan (type T) Dimensions: 1.5 cm (0.6”) diameter 3.2 cm (1.3”) length of ceramic cylinder 6.0 cm (2.4”) length of entire se nsor Weight: 10 g (0.35 oz) plus 23 g/m (0.25 oz/ft) of cable...

  • Page 9: Equilibration And Saturation Of The Sensor Before Installation

    229 Heat Dissipation Matric Water Potential Sensor 3.3 Equilibratio n and Saturation of the Sensor Before Installation The smaller the difference in water potential between the 229 ceramic an d the surrounding soil, the sooner equilibrium will be reached. Filling th e ceramic pores with liquid water will optimize the hydraulic conductivity between the ceramic and soil.

  • Page 10: Example Programs

    A Campbell Scientific datalogger can read a single thermocouple junction directly because the temperature at the wiring panel is measured with a thermistor and this temperature is converted to a voltage which is then used as a thermocouple reference.

  • Page 11: Adjusting For Thermal Properties Of Sensor During Early Heating Times7

    229 Heat Dissipation Matric Water Potential Sensor 5.2 Adjusting for Thermal Properties of Sensor During Early Heating Times The discussion presented at the beginning of the calibration section (Section 6) describes how thermal properties can vary from sensor-to-sensor. The thermal properties of the needle casing, wiring, and the amount of contact area between the needle and the ceramic have a slight effect on the temperature response.

  • Page 12: Temperature Correction

    229 Heat Dissipation Matric Water Potential Sensor The AM16/32B multiplexer in 4x16 mode provides a convenient method to measure up to sixteen 229 sensors. Since four lines are switched at once, both the thermocouple and the heating element leads for each sensor can be connected to a multiplexer channel.

  • Page 13: Example #1 - Cr1000 With Ce4 And Four 229S

    229 Heat Dissipation Matric Water Potential Sensor 5.5 Example #1 — CR1000 with CE4 and Four 229s Table 5-1 shows wiring information for reading four 229 sensors with a CR1000 datalogger and CE4 current excitation module. TABLE 5-1. Wiring for Four 229s with CR1000 and CE4 CR1000 229 #1Blue 229 #1 Green...
  • Page 14 229 Heat Dissipation Matric Water Potential Sensor 'CR1000 SequentialMode Const Num229 = 4 'Enter number of 229 sensors to measure Dim LoopCount Public RefTemp_C, StartTemp_C(Num229), Temp_1sec_C(Num229) Public Temp_30sec_C(Num229), DeltaT_C(Num229) Public Flag(1) as Boolean Units StartTemp_C()=Deg C Units DeltaT_C()=Deg C DataTable(Matric,Flag(1),-1) Sample(Num229,StartTemp_C(),FP2) Sample(Num229,DeltaT_C(),FP2) EndTable...

  • Page 15: Example #2 - Cr1000 With Am16/32-Series Multiplexer, Ce4 And Sixteen 229 Sensors With Temperature Correction

    229 Heat Dissipation Matric Water Potential Sensor 5.6 Example #2 — CR1000 with AM16/32-series Multiplexer, CE4 and Sixteen 229 Sensors with Temperature Correction Table 5-2 shows wiring information for connecting multiple 229 sensors and CE4 excitation module to an AM16/32 multiplexer and CR1000 datalogger. See Figure 6-4 for a schematic of this wiring configuration.
  • Page 16 229 Heat Dissipation Matric Water Potential Sensor 'CR1000 SequentialMode Const Num229 = 16 'Enter number of 229 sensors to measure Const read229 = 60 'Enter Number of minutes between 229-L readings Const CalTemp = 20 'Enter calibration temperature (deg C) Dim i, dTdry(Num229), dTwet(Num229) Dim Tstar, Tstarcorr, DeltaTcorr, s Public RefTemp_C, StartTemp_C(Num229), Temp_1sec_C(Num229)

  • Page 17: Example #3 - Cr10X With 229 Sensor

    229 Heat Dissipation Matric Water Potential Sensor 'Measure temperature after 30 second of heating TCDiff(Temp_30sec_C(i),1,mV2_5C,1,TypeT,RefTemp_C,True,0,_60Hz,1,0) PortSet (3,0 ) 'Set C3 low to deactivate CE4 DeltaT_C(i)=Temp_30sec_C(i)-Temp_1sec_C(i)'Calculate temperature rise Call TempCorr 'Call temperature correction subroutine dTcorr(i)=DeltaTcorr Next i EndIf 'Ends Flag(1) high condition PortSet(1,0) 'Turn multiplexer Off CallTable(Matric)
  • Page 18 229 Heat Dissipation Matric Water Potential Sensor ;{CR10X} ;Program to read 1 229-L sensor ;Reading 1 sensor takes 30 seconds *Table 1 Program 01: 60 Execution Interval (seconds) 1: If time is (P92) 1: 0 Minutes (Seconds --) into a 2: 60 Interval (same units as above) 3: 11...
  • Page 19 229 Heat Dissipation Matric Water Potential Sensor 8: Excitation with Delay (P22) ;Wait 29 more seconds for next reading 1: 1 Ex Channel 2: 0 Delay W/Ex (0.01 sec units) 3: 2900 Delay After Ex (0.01 sec units) 4: 0000 mV Excitation 9: Thermocouple Temp (DIFF) (P14) ;Take 30 second temperature reading...

  • Page 20: Example #4 - Cr10X With Am16/32-Series, Ce4, And Sixteen 229 Sensors

    229 Heat Dissipation Matric Water Potential Sensor 5.8 Example #4 — CR10X with AM16/32-series, CE4, and Sixteen 229 Sensors Table 5-4 shows wiring information for connecting multiple 229 sensors and CE4 or CE8 excitation module to an AM16/32-series multiplexer and CR10X datalogger.
  • Page 21 229 Heat Dissipation Matric Water Potential Sensor ;{CR10X} ;Program to read 16 229-L sensors using 1 AM16/32 multiplexer ;and 1 CE4 or CE8 constant current interface ;Manually set Flag 1 high to force readings *Table 1 Program 01: 30 Execution Interval (seconds) 1: Batt Voltage (P10) 1: 1 Loc [ Batt_Volt ]...
  • Page 22 229 Heat Dissipation Matric Water Potential Sensor 11: Thermocouple Temp (DIFF) (P14) ;Read thermocouple after 1 second of heating 1: 1 Reps 2: 21 10 mV, 60 Hz Reject, Slow Range 3: 1 DIFF Channel 4: 1 Type T (Copper-Constantan) 5: 2 Ref Temp (Deg.

  • Page 23: Calibration

    229 Heat Dissipation Matric Water Potential Sensor 22: Sample (P70) ;Sample 16 initial soil temperature readings 1: 16 Reps 2: 3 Loc [ Tinit_1 ] 23: Sample (P70) ;Sample 16 delta T readings 1: 16 Reps 2: 51 Loc [ dT_1 24: Do (P86) 1: 21 Set Flag 1 Low...

  • Page 24: Normalized Temperature Change And Correction For Soil Temperature

    229 Heat Dissipation Matric Water Potential Sensor correspond to the water potential expected during sensor use should be included in the calibration Temperature rise,T(30s) - T(1s), deg-C FIGURE 6-1. Data Points (x) and Regression for Typical Calibration 6.2 Normalized Temperature Change and Correction for Soil Temperature 6.2.1 Normalized Temperature Change The effect of sensor-to-sensor variability can be reduced by using normalized...

  • Page 25: Correction For Soil Temperature

    60 °C may damage the sensor cable. Reece (1996) suggested that inverse thermal conductivity can also be used a normalization technique but work by Campbell Scientific has no t shown significant advantage for this method over normalization as described by equation [3].

  • Page 26: Measurement Error For Range Of Soil Temperatures And Wide Range Of Matric Potential

    229 Heat Dissipation Matric Water Potential Sensor 1000 1500 2000 matric potential (-kPa) 10 degrees C 16 degrees C 18 degrees C 22 degrees C 24 degrees C 30 degrees C FIGURE 6-2. Measurement error for range of soil temperatures and wide range of matric potential.

  • Page 27: Measurement Error For Range Of Soil Temperatures And Wetter Range Of Matric Potential

    229 Heat Dissipation Matric Water Potential Sensor matric potential (-kPa) 10 degrees C 16 degrees C 18 degrees C 22 degrees C 24 degrees C 30 degrees C FIGURE 6-3. Measurement error for range of soil temperatures and wetter range of matric potential. A temperature correction for the difference in temperature at time of calibration and time of measurement is provided in the work of Flint et al., 2002.

  • Page 28: Using Pressurized Extraction Methods

    229 Heat Dissipation Matric Water Potential Sensor Δ 2. With the sensor in place, use the from the in situ measurement Δ Δ along with the values for the particular sensor to Δ calculate norm 3. Implement the iterative temperature correction as presented in Δ...

  • Page 29: Wiring For Calibration Using Pressure Plate Extractor

    229 Heat Dissipation Matric Water Potential Sensor Measurements of sensor temperature response are made periodically to determine if equilibration is attained. This will require depressurization of the pressure vessel if a pressure-tight feedthrough is not used. Prior to depressurization, it is important that the effluent hose be blocked by clamping or other method to prevent solution from re-entering the soil and sensors.

  • Page 30: Maintenance

    229 Heat Dissipation Matric Water Potential Sensor FIGURE 6-4. Datalogger and Peripheral Connections for 229 Calibration 7. Maintenance The 229 does not require maintenance after it is installed in the soil. The datalogger, current excitation module, and multiplexer, if used, should be kept in a weatherproof enclosure.

  • Page 31: Troubleshooting

    229 Heat Dissipation Matric Water Potential Sensor 8. Troubleshooting Symptom Possible Cause Action Temperature reading is Thermocouple wire not Check program to see which differential input offscale (-6999 or NAN) connected to correct channel 229 should be connected to and verify that it datalogger channel has a good connection to that channel Break in thermocouple wire...

  • Page 32: References

    229 Heat Dissipation Matric Water Potential Sensor 9. References Flint, A. L., G. S. Campbell, K. M. Ellett, and C. Calissendorff. 2002. Calibration and Temperature Correction of Heat Dissipation Matric Potential Sensors. Soil Sci. Soc. Am. J. 66:1439–1445. Reece, C.F. 1996. Evaluation of a line heat dissipation sensor for measuring...
  • Page 34 Campbell Scientific Companies Campbell Scientific, Inc. (CSI) 815 West 1800 North Logan, Utah 84321 UNITED STATES www.campbellsci.com • info@campbellsci.com Campbell Scientific Africa Pty. Ltd. (CSAf) PO Box 2450 Somerset West 7129 SOUTH AFRICA www.csafrica.co.za • cleroux@csafrica.co.za Campbell Scientific Australia Pty. Ltd. (CSA)

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