Campbell Scientific KH20 User Manual

KH20 Krypton Hygrometer

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Copyright © 2010

Campbell Scientific, Inc.

Warranty and Assistance

The KH20 KRYPTON HYGROMETER 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, INC.'s obligation under this warranty is limited to repairing or
replacing (at CAMPBELL SCIENTIFIC, INC.'s option) defective products.
The customer shall assume all costs of removing, reinstalling, and shipping
defective products to CAMPBELL SCIENTIFIC, INC. CAMPBELL
SCIENTIFIC, INC. will return such products by surface carrier prepaid. This
warranty shall not apply to any CAMPBELL SCIENTIFIC, INC. products
which have been subjected to modification, misuse, neglect, accidents of
nature, or shipping damage. This warranty is in lieu of all other warranties,
expressed or implied, including warranties of merchantability or fitness for a
particular purpose. CAMPBELL SCIENTIFIC, INC. is not liable for special,
indirect, incidental, or consequential damages.

Products may not be returned without prior authorization. The following
contact information is for US and International customers residing in countries
served by Campbell Scientific, Inc. directly. Affiliate companies handle
repairs for customers within their territories. Please visit
www.campbellsci.com to determine which Campbell Scientific company
serves your country.

To obtain a Returned Materials Authorization (RMA), contact CAMPBELL
SCIENTIFIC, INC., phone [phone]. After an applications engineer
determines the nature of the problem, an RMA number will be issued. Please
write this number clearly on the outside of the shipping container.
CAMPBELL SCIENTIFIC's shipping address is:

CAMPBELL SCIENTIFIC, INC.

RMA#_____
815 West 1800 North
Logan, Utah 84321-1784

For all returns, the customer must fill out a “Declaration of Hazardous Material
and Decontamination” form and comply with the requirements specified in it.
The form is available from our website at
completed form must be either emailed to [e-mail]
435-750-9579. Campbell Scientific will not process any returns until we
receive this form. If the form is not received within three days of product
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customer’s expense. Campbell Scientific reserves the right to refuse service on
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concerns for our employees.

www.campbellsci.com/repair

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or faxed to

KH20 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

2. Specifications ..............................................................1

2.1 Measurements...........................................................................................1

2.2 Electrical...................................................................................................1

2.3 Physical..................................................................................................... 2

3. Installation....................................................................2

3.1 Siting.........................................................................................................2

3.2 Mounting ..................................................................................................2

3.2.1 Parts and Tools Needed for Mounting............................................2

3.2.2 Mounting the KH20 Sensor............................................................3

3.2.3 Mounting the Electronics Box ........................................................3

4. Wiring............................................................................5

5. Datalogger Programming............................................6

5.1 KH20 Calibration .....................................................................................6

5.2 Example 1, CR3000 Program to Measure Water Vapor Fluctuations......7

6. Maintenance and Calibration......................................9

6.1 Visual Inspection......................................................................................9

6.2 Testing the Source Tube...........................................................................9

6.3 Testing the Detector Tube ........................................................................9

6.4 Managing the Scaling of KH20..............................................................10

6.5 Older KH20 ............................................................................................10

6.6 Calibration..............................................................................................10

Appendix

A. Calibrating KH20..................................................... A-1

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

A-1. KH20 ln(mV) vs. Vapor Density....................................................... A-2

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KH20 Table of Contents

Tables

1. Datalogger Connections for Differential Measurement............................. 5

2. KH20 Calibration Ranges.......................................................................... 6

A-1. Linear Regression Results for KH20 ln(mV) vs. Vapor Density ...... A-2

A-2. Final Calibration Values for KH20.................................................... A-3

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KH20 Krypton Hygrometer

1. General Description

The KH20 is a krypton hygrometer for measuring water vapor fluctuations in
the air. The name KH20 (KH-twenty) was derived from KH2O (K-H
the sensor has been known with this name since 1985. It is typically used with
the CSAT3 3-D sonic anemometer for measuring latent heat flux (LE), using
Eddy Covariance technique. Please refer to the Open Path Eddy Covariance
System operator’s manual for details on flux measurements using the KH20
sensor.

The KH20 sensor uses a krypton lamp that emits two absorption lines: major
line at 123.58 nm and minor line at 116.49 nm. Both of these lines are
absorbed by water vapor, and a small amount of the minor line is absorbed by
oxygen. The KH20 is not suitable for absolute water vapor 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
(CSI p/n 14113) that protects them from moisture. The KH20 is suitable for
long-term continuous outdoor applications.

The KH20 sensor is comprised of two main parts: the sensor head and the
electronics box. The sensor head comes with cables with 6 ft of lead length
that connect the sensor to the electronics box. It is shipped with a rain shield
(CSI p/n 14113) to protect the electronics box and the connectors from
moisture, a 20 inch 3/4 IPS threaded aluminium pipe (CSI p/s 3874), a 3/4” x
3/4” Nu-Rail (CSI p/n 1017), and a 5/32 inch Allen wrench (CSI p/n 4697) for
mounting. The sensor comes with a signal/power cable which has 25 ft lead
length. If a longer cable is desired, the customer can order a replacement cable
(p/n KH20CBL-L) and specify the desired lead length after -L.

O), and

2

NOTE

Discussion on the principles and theory of measurement is
included in Appendix A.

2. Specifications

2.1 Measurements

Calibration Range: 1.7 to 19.5 g/m3 (nominal)
Frequency Response: 100 Hz
Operating Temperature Range: -30 to +50°C

2.2 Electrical

Supply Voltage: 10 V to 16 Vdc
Current Consumption: 20 mA max at 12 Vdc
Power Consumption: 0.24 Watts
Output Signal Range: 0 to 5Vdc

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KH20 Krypton Hygrometer

2.3 Physical

Dimensions
Sensor Head: 11.5” x 9” x 1.25” (29 cm x 23 cm x 3 cm)
Electronics Box: 7.5” x 5” x 2” (19 cm x 13 cm x 5 cm)
Rain Shield with Mount: 11.5” x 7” x 2.5” (29 cm x 18 cm x 6.5 cm)
Mounting Pipe: 20” (50 cm)
Carrying Case: 25” x 15” x 7” (64 cm x 38 cm x 18 cm)
Weight
Sensor Head: 3.55 lbs (1.61 kg)
Electronics Box: 1.4 lbs (6.4 kg)
Rain Shield with Mount: 4.75 lbs (2.2 kg)
Mounting Pipe with Nu-rail: 1.0 lbs (0.45 kg)
Carrying Case: 9.45 lbs (4.3 kg)
Shipping: 20.15 lbs (9.2 kg)
Package Includes:
KH20 sensor head with 5’ of cables
Power/Signal cable with 25’ lead length (CSI p/n KH20CBL-L)
Electronics Box
Rain Shield (CSI p/n 14113)
Horizontal Mounting Boom (20 inch 3/4” IPS threaded aluminium pipe)
(CSI p/n 3874)
Nu-rail (3/4” x 3/4”) (CSI p/n 1017)
Allen Wrench (5/32”) (CSI p/n 4697)

3. Installation

3.1 Siting

3.2 Mounting

3.2.1 Parts and Tools Needed for Mounting

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.

You will need the following hardware to mount the KH20 sensor:

1. Tripod (CSI model CM115 standard) or tower

2. CM20x series crossarm (CSI model CM204 standard)

3. 3/4 inch IPS Aluminum Pipe, 12 inches long (CSI p/n 18048)

4. 3/4” x 1” Nu-rail (CSI p/n 1049)

5. Small Phillips and flat-head screw-drivers

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6. 1/2 inch wrench