The SR430 Multichannel Scaler/Averager can be thought of as a photon counter that counts events as a function of time. A trigger starts the counter which segments photon count data into sequential time bins (up to 32k bins). The width of the bins can be set from 5 ns to 10 ms. The instrument records the number of photons that arrive in each bin. It combines amplifiers, discriminators, bin clocks, and data analysis in a single, integrated instrument. IEEE-488, RS232 , and printer/plotter interfaces are standard. A built-in 3.5 inch disk drive permits easy import and export of data. The SR430 is useful in a variety of applications where it is necessary to count events as a function of time: LIDAR, time of flight mass spectroscopy, and fluorescence decay measurements are just a few examples.