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Chameleon - Configurations


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The Chameleon - known for its ability to change colours...
Any built Chameleon instrument can be described by a simple functional designator in the format (CFN)-λ-(LC).

The first letter indicates the intended function of the instrument :

C = colorimeter, F = fluorometer, N = nephelometer (for measurement of 900 light scattering)

The colour of the instrument's (LED) light source is next indicated numerically by λ, the nominal source wavelength in nanometers (nm). Most LED's have a fairly broad spectral output; λ is the peak emission wavelength. For a white LED, replace λ with the letter W.

The actual choice of source wavelength will be dictated by the spectroscopy involved (i.e. at what wavelength does your sample absorb ?).

The final letter denotes the mode by which the instrument will output its data:

L = LCD display
C = computer

For example, if one requires a stand-alone instrument to measure quinine fluorescence excited at 370 nm and having an LCD readout we would build an F-370-L. An instrument used in flow-injection analysis (FIA) for the colorimetric determination of phosphate at 880 nm with computer data logging would be a C-880-C. Finally an instrument for light scattering measurements with a white LED and an LCD readout would be an N-W-L.

Chameleon - Features

  • WavelengthsAny source wavelength from 350 nm to 1μm is possible using a low cost LED driven by a constant current source for excellent intensity stability.
  • DetectorsUser can select from a choice of two low-noise, solid-state detectors - a TSL230 light-to-frequency converter for in-line/900 detection, or a TSL25x light-to-voltage converter (for 900 detection).
  • Signal ProcessingAll data acquisition, signal averaging and processing tasks are managed by a dedicated 8 pin PIC flash microcontroller programmed in C.
  • Data LoggingData logging is possible via a USB connection using LabVIEWTM, enabling the instrument to be used as a flexible detection system e.g. in FIA experiments.
  • Scattered Light RejectionAn optical filter can be installed in front of the detector to discriminate against scattered light in fluorescence applications.
  • Cuvette HolderInstrumentation is mounted inside a Delrin housing with a central cavity to accept either a standard 1 cm cuvette or a flow-through cell; this has an internal ball plunger to ensure accurate and repeatable cuvette alignment.
  • Materials CostTotal cost of electronic components is approximately $10; to build a complete instrument including PCB, enclosure and USB cable typically costs $50-$100.
  • AssemblyAssembly of a Chameleon spectrometer can be performed by anyone reasonably proficient with a soldering iron in less than an hour. An instrument has even been constructed and a full analytical experiment performed using it within a single 3 hour laboratory session !
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