Dual Wavelength U.V.-Vis. Photometer

Version 1.0 (June, 2000). Click to see a larger view.

[Operating instructions] [Cell definitions and equations]

Simulation of a dual-wavelength uv-visible spectrophotometer with a 200 - 800 nm wavelength range, switchable tungsten and deuterium light sources, four interchangable quartz cuvettes, auto-zero button, four readout modes, and realistic sources of error and non-linearity. Students specify sample characteristics, select wavelength, cell path length, select deuterium or tungsten lamp, and perform measurements. Realistic modeling of lamp spectral characteristics, cell transmission variations, photon and detector noise, unabsorbed stray light, and instrument non-linearity caused by finite spectral bandpass.

Version 1.0 (June, 2000) has a fixed 5 nm spectral bandpass and models a single absorber in solution. Allows the student to specify the solute weight, solution volume, and the absorptivity, peak wavelength, and peak width of the absorber in each of the four cells. Version 1.1 (July, 2000) models a mixture of two absorbers (A and B) in solution.

Download links: Version 1.0 (June, 2000): DualWave.WKZ; Version 1.1 (July, 2000): dws11.wkz;

Wingz player application and basic set of simulation modules, for windows PCs or Macintosh

Other related simulations:
U.V.-Visible Spectrophotometer
Instrumental Deviations from Beer's Law
Comparison of Calibration Curve Fitting Methods in Absorption Spectroscopy
Signal-to-noise ratio of absorption spectrophotometry
Effect of Slit Width on Signal-to-Noise Ratio in Absorption Spectroscopy

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Operating Instructions:

Specify the spectral characteristics and concentrations of the absorbers in the four cell by typing values into the Cuvette Changer table (cells C9 .. F13). Use the sliders above to change the wavelengths of the two monochromators. Click on the buttons on the lower left to change the cell path length and lamp type. Click on one of the four cuvette buttons (#1 ... #4) to change the cuvette in the light beam. (The current selections are highlighted in red). Click one of the four radio buttons below the absorbance readout to select the readout mode: A1 (absorbance at wavelength 1), A2 (absorbance at wavelength 2), difference mode (A1-A2), or ratio mode (A1/A2). Click the Auto-zero button to zero the readout on the current cell contents. Click the Read once button to take a single reading of absorbance. Click on the Read 30 times button to take 30 readings in quick succession (without removing and replacing the cell) and calculate the mean (average), standard deviation, and percent relative standard deviation of the readout. Click on the Replace 30 times button to simulate removing and replacing the cuvette 30 times (including the effect of changes in background transmission due to cell repositioning error, dust on the cell, particles in solution, etc).

Cell definitions and equations