Campbell KH20 User Manual
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Campbell KH20 User Manual

Krypton hygrometer
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KH20
Krypton
Hygrometer
User Manual
Issued 23.3.10
©
Copyright
2010 Campbell Scientific Inc.
Printed under Licence by Campbell Scientific Ltd.
.
CSL 876

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Summary of Contents for Campbell KH20

  • Page 1 KH20 Krypton Hygrometer User Manual Issued 23.3.10 © Copyright 2010 Campbell Scientific Inc. Printed under Licence by Campbell Scientific Ltd. CSL 876...
  • Page 3 Note that goods sent air freight are subject to Customs clearance fees which Campbell Scientific will charge to customers. In many cases, these charges are greater than the cost of the repair. Campbell Scientific Ltd,...
  • Page 5 PLEASE READ FIRST About this manual Please note that this manual was originally produced by Campbell Scientific Inc. primarily for the North American market. Some spellings, weights and measures may reflect this origin. Some useful conversion factors: Area: 1 in...

  • Page 7: Table Of Contents

    A.1 Basic Measurement Theory ..............A-1 A.2 Calibration of KH20 ................A-1 Figures 1. Mounting KH20 onto a tripod ..............3 2. Proper mounting position of the electronics box ........4 3. Attaching cables to the electronics box ............5...
  • Page 8 Tables 1. Datalogger Connections for Differential Measurement ......5 2. KH20 Calibration Ranges ................6 A-1. Linear Regression Results for KH20 ln(mV) vs. Vapour Density ..A-2 A-2. Final Calibration Values for KH20 ............ A-3...

  • Page 9: General Description

    KH20 is not suitable for absolute water vapour concentration measurements due to its signal offset drift. The KH20 heads are sealed and will not suffer damage should they get wet. In addition, the electronics box and the connectors are housed inside a rain shield (#14113) that protects them from moisture.

  • Page 10: Physical

    3. Installation 3.1 Siting When installing the KH20 sensor for latent heat flux measurement in an eddy covariance application, proper siting, sensor height, sensor orientation and fetch are important. Please refer to Section 2 Installation and Mounting of the Open Path Eddy Covariance System manual for more discussion on siting.

  • Page 11: Mounting The Electronics Box

    3. Mount the 12 inch long pipe (#18048) to a crossarm via 1” x 3/4” Nu-rail (#1049). 4. Mount the KH20 onto the 12” long pipe using a 3/4” x 3/4” Nu-rail (#1017). Mount the KH20 such that the source tube, the longer of the two tubes, is positioned on top, as shown in Figure 1.

  • Page 12: Proper Mounting Position Of The Electronics Box

    3. Mount the rain shield onto the tripod or tower mast using the U-bolt provided. Make sure that the distance between the KH20 sensor head and the rain shield is within 5 feet so that the cables from the sensor head will be within reach of the electronics box.

  • Page 13: Wiring

    6. Gather any loose cables and tie them up, using cable ties, onto the tripod or tower mast. 4. Wiring The KH20 sensor is shipped with a power/signal cable with a 25 ft standard lead length. Table 1 shows the connections for the KH20 to the CR1000, CR3000, and CR5000.

  • Page 14: Datalogger Programming

    The water vapour absorption coefficient for three different vapour ranges are calculated from the collected calibration data: full range, dry range, and wet range. Table 2 shows a sample of the KH20 vapour ranges over which three different water vapour absorption coefficients are calculated. See Appendix A for more information on KH20 calibration.

  • Page 15: Example 1, Cr3000 Program To Measure Water Vapour Fluctuations

    'CR3000 Series Datalogger 'This datalogger program measures KH20 Krypton Hygrometer. 'The station operator must enter the constant and the calibration value for the KH20. 'Search for the text string "unique" to find the locations of these constants 'and enter the appropriate values found from the calibration sheet of the KH20.

  • Page 16: Maintenance And Calibration

    NextScan EndProg 6. Maintenance and Calibration The KH20 sensor is designed for continuous field application and requires little maintenance. The tube ends for the KH20 have been sealed with silicone elastomer using an injection-mould method. Therefore, the tubes are protected from water damage, and the KH20 continues to make measurements under rainy or wet conditions.

  • Page 17: Visual Inspection

    Section 6.3 below. 6.3 Testing the Detector Tube If the source tube tests fine but the output from KH20 is still in question, perform the following test. Prepare a piece of paper and insert it between the source tube and the detector tube to completely block the optical path. You should see an immediate decrease in the voltage reading, and it should go close to zero.

  • Page 18: Older Kh20

    The older version of the KH20 used to suffer permanent damage when exposed to water, due to corrosion and loss of vacuum within the tubes. The new version of the KH20 has employed a new sealing around the window to prevent this type of damage.

  • Page 19: Calibrating Kh20

    ρ. The KH20 sensor uses the UV light emitted by the krypton lamp: major line at 123.58 nm and the minor line at 116.49. As the light travels through the air, both the major line and the minor line are absorbed by the water vapour present in the light path.
  • Page 20 ρ . Campbell Scientific, Inc. performs the calibration twice for each KH20: once with the window cleaned, and again with the window scaled. We then break up the vapour density range into dry and wet ranges, and compute the k values for each sub range, as well as for the full range.
  • Page 21 Appendix A. Calibrating KH20 Table A-2. Final Calibration Values for KH20 Vapour Range Slope Y Intercept Coefficient (g/m ln (V Full Range 1.74 ~ 19.25 -0.205 3087 -0.144 Dry Range 1.74 ~ 9.20 -0.216 3259 -0.151 Wet Range 7.95 ~ 19.25 -0.201...
  • Page 22 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 Scientific Australia Pty. Ltd. (CSA)

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