A Simple System for Real-Time Digital Acquisition of Fast Kinetic Data

Abstract

We have assembled a data acquisition system (DAS) for the study of fast kinetics, specifically transient light absorption by molecular species formed by single pulses from a Q‐switched laser. The DAS consists of a sample‐and‐hold amplifier, 10‐bit analog‐to‐digital converter, solid state (MOS) memory, and associated timing and control circuitry. The analog signal (e.g., from a photomultiplier‐preamplifier circuit) is sampled at preset times, converted to binary digital form, and stored in the memory. The nominal accuracy of A‐to‐D conversion is ±0.05%, and the time between sampled points can be as short as 1.25 μsec. Following each laser flash, the data points are read sequentially from the memory, translated from binary to decimal numbers, and delivered to a digital panel display and a paper tape punch. The punched tape is then used to enter the data into a time shared computer for detailed analysis. The system can be readily adapted for on line use and can be used in conjunction with any of the various techniques available for studying fast chemical and biological processes [see, e.g., Methods in Enzymology, edited by K. Kustin (Academic, New York, 1969), Vol. 16].