The pulse counter circuit comprises an oscillator (1) of which the frequency is controlled by a probe, a constant frequency oscillator (13), a gate circuit (16) and a pulse counter (18). Such pulse counter circuits find application to flow measurements, particularly for calorimetric measurements. The aim is to provide a counter circuit allowing an accurate counting of the pulses during a predetermined period while being considerably less costly than the devices used heretofore. The solution is provided by transmitting the output voltage (5) of the pulses from the frequency controlled oscillator (1) through a period discriminator (8) to the gate circuit (16) and by coupling the other input of the gate circuit to the output (14) of the constant frequency oscillator (13).