Random error in timing using weak light pulse, photomultiplier, and threshold crossing detection

Expressions are reported which determine the random timing error resulting from random phenomena occurring during time points marking with weak light pulses, received by photomultiplier and detected by constant fraction and constant threshold discriminators. Examples of applications are receivers for laser-pulse, earth-to-satellite distance measuring instruments, and scintillation counters used in nuclear events timing. Results of calculations obtained from the formulas are in accordance with the results coming from simulations