PowerPoint-Pr

1
Field-Portable Spectroscopy
Introduction

• Field-portable spectroscopy has traditionally
  been used in remote sensing applications.
• The technology can be used for on site analysis
  of soils and agricultural inputs and products.
• Field-portable spectroscopy utilizes diffuse
  reflectance of light in the visible (350-750 nm)
  and near infrared (750-2,500 nm) wavelength
  regions of the electromagnetic spectrum (Fig. 1).
  
• The measured spectrum (Fig. 2) contains
  interpretable information about the composition,
  structure, and concentration of substances in a
  sample.

Figure 1 The electromagnetic spectrum
Figure 2. Visible near infrared spectrum of a
soil sample.
Instrumentation
Key Advantages/Limitations

• Portable
• Useful for field applications
• Little sample preparation
• Rapid acquisition of unprocessed samples
• Low cost instrument
• Visible wavelength range gives information on
  iron oxides in soil

• Field-portable instruments can run on battery
  power.
• Reflected light is gathered through a fibre-optic
  cable. An integrating sphere with an external
  light source can be used.

• External white reference is required
• No internal reference or validation available
• Instrument needs annual service at factory
• Reproducibility across instruments and over time
  is unknown
• Readings are sensitive to movement of the
  fibre-optic cable

Field-portable spectrometer fitted with an
integrating sphere containing an integrated light
source. In this example a soil sample contained
in a Petri dish is being scanned.
Contact World Agroforestry Centre (ICRAF), P.O.
Box 30677-00100 Nairobi, Kenya. Tel [phone]
4000. www.worldagroforestry.org