Abstract: A measuring method and apparatus wherein the value of a physical quantity is measured by means of a first measuring device (2, 3) producing at its output an electrical voltage or current, which is a function of the value of the said physical quantity; wherein, simultaneously, a reference value for this physical quantity is measured by means of a second measuring device (2, 4), which is identical to the said first measuring device; wherein the output voltage or current of the said first measuring device (3) is applied to one of the measuring inputs (10, 11) of an analog/digital converter (9) with a variable threshold value; wherein the output voltage or current of the said second measuring device (4) is applied to the other measuring input (11, 10) of this analog/digital converter (9) and wherein the digital output signal of the said analog/digital converter (9) is applied to a processing and/or data display device (14).