A Cherenkov proton-beam monitor has been investigated. Its electronic system consisting of a preamplifier and an amplifier of detector signals is described. The measured waveform is compared to the simulated monitor signals during proton detection. The relative variance of the photomultiplier-tube gain for single photoelectrons has been measured. Good agreement is observed between the results of measurements with the monitors and the induction sensor of the proton-beam current. The monitor is incapable of detecting photons and electrons with energies below 170 keV, which is important for suppressing low-energy background.