A pulse generator simulating slit-scan chromosome analysis signals

A simple circuit is described for generating a variety of electronic pulses to test hardware and software for slit-scan chromosome analysis in a flow cytometer. The pulse shape can be changed to have different numbers of local minima, thereby simulating fluorescence pulses from acrocentric, monocentric, and dicentric chromosomes. Long pulses simulate aggregates of chromosomes. The pulse repetition rate as well as the pulse amplitude is variable. Although the circuitry is built with only three integrated circuits, the pulse-to-pulse variation in shape and height is quite small. After digitization of the analog signals, the constructed histograms of pulse integrals show a relative coefficient of variation below 1%. This signal generator provides a valuable tool for a number of electronic test applications that would otherwise require expensive standard particles analyzed in a well-tuned flow cytometer.