Abstract: A method is provided to ascertain the total number of cells per unit volume of a cell specimen in an apparatus which does not measure the volume of a suspension containing the specimen as it is being analyzed. The method includes mixing a suspension of a known quantity of particles having a first light scatter signal with a known volume of a cell specimen having a second light scatter signal different from the first light scatter signal to obtain a suspension having a concentration of particles per specimen volume, passing each of said particles and each cell in said cell specimen, in turn, through a light beam, each of said particles and cells producing at least one forward light scattering pattern, counting the number of cells and the number of particles in a portion of said suspension, and determining the total number of cells per unit volume of the specimen.

Abstract: A flow cytometer includes a plurality of detectors for providing voltage pulse signals over a four decade range as particles pass through an illuminated detection station. Each voltage pulse signal is processed and provided to a first sample and hold for storage. Thereafter, the value in the first sample and hold is amplified by one or thirty-two, depending upon its magnitude, and stored in a second sample and hold for subsequent provision to a sixteen bit analog to digital convertor (ADC), one signal at a time. The first sample and hold is then free to store a new value while the old value is awaiting provision to the ADC. The ADC converts the signal received from the second sample and hold to a fifteen bit digital signal and uses the sixteenth bit to manifest whether the signal stored in the second sample and hold was amplified by thirty-two.