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Rosing, R.; Kerkhoff, Hans G.; Tangelder, R.J.W.T.; Sachdev, Manoj

doi:10.1023/a:1008349322397

Cited by 6 publications

(1 citation statement)

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“…Coherent sampling requires that an integer number of wanted waveforms exist in the acquired data set and that the ratios between the sampling and the modulation frequencies ͑both laser scanning and laser modulation signals͒ are integers. [15][16][17] With this technique a number of scanned signals can be averaged before the lock-in detection is carried out. Periodic noise such as power supply ripple and external optical noise from fluorescent lamps, etc., which does not fulfill the requirements above, is averaged out ͑the coherent sampling process acts as a comb filter͒ together with nonperiodic noise.…”

Section: Introductionmentioning

confidence: 99%

Flexible lock-in detection system based on synchronized computer plug-in boards applied in sensitive gas spectroscopy

Andersson

Persson

Svensson

et al. 2007

Review of Scientific Instruments

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We present a flexible and compact, digital, lock-in detection system and its use in high-resolution tunable diode laser spectroscopy. The system involves coherent sampling, and is based on the synchronization of two data acquisition cards running on a single standard computer. A software-controlled arbitrary waveform generator is used for laser modulation, and a four-channel analog/digital board records detector signals. Gas spectroscopy is performed in the wavelength modulation regime. The coherently detected signal is averaged a selected number of times before it is stored or analyzed by software-based, lock-in techniques. Multiple harmonics of the modulation signal (1f, 2f, 3f, 4f, etc.) are available in each single data set. The sensitivity is of the order of 10(-5), being limited by interference fringes in the measurement setup. The capabilities of the system are demonstrated by measurements of molecular oxygen in ambient air, as well as dispersed gas in scattering materials, such as plants and human tissue.

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Section: Introductionmentioning

confidence: 99%