Details

Autor(en) / Beteiligte

• Rusak, David A.
• Kawka, Ernest A.
• Trexler, E. Brady

Titel

Note: Investigation of a null measurement of optical absorbance using a pulse width modulated light-emitting diode

Ist Teil von

• Review of scientific instruments, 2010-01, Vol.81 (1), p.016107-016107

Ort / Verlag

United States

Erscheinungsjahr

2010

Quelle

MEDLINE

Beschreibungen/Notizen

• We examined the possibility of making a null measurement of optical absorbance by using pulse-width modulation to control the intensity of a light-emitting diode (LED). This type of measurement is intriguing because the instrumental sources of noise are different from those in the traditional absorbance measurement. Our experiment employed phototransistor detectors and a RC integrator to measure the amount of light being transmitted. However, instead of measuring the ratio of the detector voltages for a blank and sample, we measured the ratio of the LED duty cycles required to give the same detector voltage for a blank and a sample. Using this method, it is presumed that  the same amount of light reaches the detector during measurement of the blank and sample.