Abstract: Device for measuring a signal having a very high noise level by an integrator circuit having an operational amplifier, characterized in that the device comprises a means for memorizing a voltage representative of the charge of the capacitor of the integrator circuit, a means for switching the voltage in the memory onto the integration capacitor to bring the voltage of that capacitor to a value close to the asymptotic integration value and a time base for controlling that switching and the reading of the final integration value.

Abstract: Phase correlator between a wave having a frequency of F sent out by an oscillator and a useful signal having the same frequency F and having a relative phase .phi..sub.0, comprising a first and a second modulator effecting the modulation of the useful signal having a high noise level by the wave out by the oscillator on the one hand through an adjustable phase-shifter of .phi. and on the other hand through the phase-shifter of .phi. followed by a fixed phase-shifter of .phi..sub.1, an adjusting circuit of .phi. by the error signal between the two preceding modulation signals coming respectively from two integrators and a third modulator effecting the modulation of the signal having a high noise level by the wave sent out by the oscillator through another phase-shifter of .phi.1/2 connected with the phase-shifter.