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Campbell Bowen Ratio Instrumentation Instruction Manual

Summary of Bowen Ratio Instrumentation

  • Page 1

    Instruction manual bowen ratio instrumentation revision: 9/05 c o p y r i g h t ( c ) 1 9 8 7 - 2 0 0 5 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

    Warranty and assistance the bowen ratio instrumentation 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. Campbell scientific...

  • Page 3

    I bowen ratio 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. System overview ......................................................1-1 1.1 review of theory ....................

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    Bowen ratio table of contents ii figures 1.2-1. Vapor measurement system............................................................. 1-3 1.2-2. Thermocouple configuration............................................................ 1-4 2-1. Csi bowen ratio system .......................................

  • Page 5: Section 1.  System Overview

    1-1 section 1. System overview 1.1 review of theory by analogy with molecular diffusion, the flux-gradient approach to vertical transport of an entity from or to a surface assumes steady diffusion of the entity along its mean vertical concentration gradient. When working within a few meters of the s...

  • Page 6

    Section 1. System overview 1-2 ( ) ( ) β λε = = − − h l pc t t e e e p 1 2 1 2 (6) where pc p λε is the psychrometric constant. The surface energy budget is given by, r g h l n e − − − = 0, (7) where r n is net radiation for the surface and g is the total soil heat flux. The sign convention used is ...

  • Page 7: 1.2  System Description

    Section 1. System overview 1-3 figure 1.2-1. Vapor measurement system 1.2 system description 1.2.1 water vapor measurement it is common practice in bowen ratio measurements to measure wet bulb depression to develop the water vapor gradient. The position of the two psychrometers is periodically rever...

  • Page 8

    Section 1. System overview 1-4 a datalogger is used to measure all sensors and control the valve that switches the air stream through the cooled mirror. The resolution of the dewpoint temperature measurement is ±0.003°c over a ±35°c range. The limitation is the stability of the dew-10, approximately...

  • Page 9

    Section 1. System overview 1-5 the gradient measurement is due only to the difference in the radiative heating of the two tc junctions and their physical symmetry minimizes this. Conversely, contamination of only one junction can cause larger errors. Applying temperature gradients to the tc connecto...

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    Section 1. System overview 1-6 this is a blank page..

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    2-1 section 2. Station installation figure 2-1 shows the typical bowen ratio installation on the cm10 tripod. The 023a enclosure, mounting arms, and sp20r solar panel all mount to the tripod mast (1 1/4 in. Pipe, inside diameter) with u-bolts. The size of the tripod allows the heights of the arms to...

  • Page 12

    Section 2. Station installation 2-2 q7-br (system) figure 2-1. Csi bowen ratio system 2.2 soil thermocouples and heat flux plates the soil thermocouples and heat flux plates are typically installed as shown in figure 2.2-1. The tcav parallels four thermocouples together to provide the average temper...

  • Page 13

    Section 2. Station installation 2-3 to minimize thermal conduction down the sensor lead wires, they should be buried for a short distance back from the sensor. In particular, do not run the leads directly to the surface, but wrap them around the edge of the hole, keeping the leads at the same level ...

  • Page 14: 2.3  Wiring

    Section 2. Station installation 2-4 figure 2.2-2. Tcav spatial averaging thermocouple probe 2.3 wiring table 2.3-1 lists the connections to the cr23x for the standard bowen ratio sensors measured by the example program. Because the air temperature measurements are so critical, the air temperature th...

  • Page 15

    Section 2. Station installation 2-5 upper/lower tcs - constantan red/red tc shield clear/clear 5h hft#1 black 5l hft#2 white/white hft#1 and hft#2 clear/clear 6h wind sentry red 6l cs615 green wind sentry white/clear cs615 black/clea r ex1 hygrometer excitation red ex2 wind sentry black gnd hygromet...

  • Page 16

    Section 2. Station installation 2-6 c r 2 3 x figure 2.3. A block diagram for the connections between the datalogger, the br relay driver and components, and the external battery..

  • Page 17: 2.4  Battery Connections

    Section 2. Station installation 2-7 2.4 battery connections two terminal strip adapters for the battery posts (p/n 4386) are provided with the 023a (figure 2.4-1). These terminal strips will mount to the wing nut battery posts on most deep cycle lead acid batteries. Figure 2.4-1. Terminal strip adap...

  • Page 18: 2.7  Cleaning The Dew 10

    Section 2. Station installation 2-8 thermocouples. A camel-hair brush and tweezers can be used to clean the thermocouples. To turn the hygrometer and pump on, set flag 6 high. The thermocouples can also be dipped in a mild acid to dissolve spider webs. For example, muratic acid (hydrochloric acid) i...

  • Page 19

    Section 2. Station installation 2-9 if the led is not already on, turn the potentiometer clockwise until it turns on and then counter clockwise until it goes off. Now, slowly turn the potentiometer clockwise until the led comes on again. 7. Return the switch to its normal operating position. The led...

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    Section 2. Station installation 2-10 this is a blank page..

  • Page 21

    3-1 section 3. Sample cr23x program the example program is available on the campbell scientific ftp site, ftp://ftp.Campbellsci.Com/pub/outgoing/files/br_023a.Exe. The example program measures the standard bowen ratio inputs: vapor pressure and air temperature gradients, net radiation, and soil heat...

  • Page 22

    Section 3. Sample cr23x program 3-2 table 3-1. Sample cr23x bowen ratio program flow chart table 1 1 second execution interval measure panel temperature measure lower thermocouple (single ended) measure upper thermocouple (differential) measure rtd on cooled mirror subtract upper tc temp. From the l...

  • Page 23

    Section 3. Sample cr23x program 3-3 table 2 10 second excitation interval yes 40 second interval ? No reset flag 1 yes flag 5 set ? No yes flag 4 reset ? No call subroutine 1 yes 2 minute interval ? No set flag 1 yes 4 minute interval ? No set port 2 high set flag 2 set port 1 high reset flag 2 dela...

  • Page 24

    Section 3. Sample cr23x program 3-4 subroutine 1 output the time processing is re-enabled reset flag 5 (re-enable output) [output process] day, hour:minute subroutine 2 turn the cooled mirror and pump on/off in response to a user flag or battery voltage yes flag 6 set ? No set port 3 high (turn on p...

  • Page 25

    Section 3. Sample cr23x program 3-5 table 3-2. Output from example bowen ratio program 01: 110 20 minute bowen ratio data 02: day 03: hhmm 04: avg reference temperature 05: avg t low 06: avg dt 07: avg dp low 08: avg vp low 09: avg dp high 10: avg vp high 01: 237 20 minute bowen ratio data 02: day 0...

  • Page 26

    Section 3. Sample cr23x program 3-6 this is a blank page..

  • Page 27: Split

    4-1 section 4. Calculating fluxes using split split (loggernet software) can be used to calculate the fluxes from the bowen ratio measurements. This section describes these calculations on the data output from the example datalogger program. It requires two passes with split to compute the fluxes. T...

  • Page 28

    Section 4. Calculating fluxes using split 4-2 heat of the soil and the change in soil temperature, ∆t s , over the output interval, t, are required to calculate the stored energy. The heat capacity of the soil is calculated by adding the specific heat of the dry soil to that of the soil water. The v...

  • Page 29

    Section 4. Calculating fluxes using split 4-3 table 4.2-1. Input values for flux calculations varib. Value units description cp 1.01 kj/(kg k) specific heat of air cw 4190.0 j/(kg k) specific heat of water cs* 840.0 j/(kg k) specific heat of dry soil (estimate) ew** 2450.0 kj/kg latent heat of vapor...

  • Page 30

    Section 4. Calculating fluxes using split 4-4 this is a blank page..

  • Page 31: Appendix A.  References

    A-1 appendix a. References bowen, i. S., 1926: the ratio of heat losses by conduction and by evaporation from any water surface. Phys. Rev., 27, 779-787. Brutsaert, w., 1982: evaporation into the atmosphere. D. Reidel publishing co., 300 pp. Dyer, a. J., and w. O. Pruitt, 1962: eddy flux measurement...

  • Page 32

    Appendix a. References a-2 wallace, j. M., and p. V. Hobbes, 1977: atmospheric science: an introductory survey. Academic press, 350 pp..

  • Page 33: 1993)

    B-1 appendix b. 023 bowen ratio (pre july 1993) figure b-1. 023 bowen ratio vapor measurement system with three flowmeters.

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    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 sales@csafrica.Co.Za campbell scientif...