The invention is a method for checking the operation of at least one sensor situated in a dialysis liquid circuit of an artificial kidney. The method includes causing a reference liquid of known characteristics to circulate in the extracorporeal blood circuit, taking a measurement to check at least one characteristic of the dialysis liquid by means of the sensor, calculating the theoretical value of at least one characteristic of the reference liquid on the basis of the measurement, comparing the calculated theoretical value with the known value of the said characteristic of the reference liquid, concluding that the sensor is working properly after the measurement has been taken when the calculated theoretical value is substantially equal to the known value. A device for the application of this method is also disclosed.