Abstract: A device and a method for reading a mechanical numerical totalizer meter having a plurality of decadic wheels is disclosed. The device includes a light source for illuminating a portion of a decadic wheel, a sensor for detecting a change in the intensity of light reflected by the illuminated portion of the decadic wheel and for linearly scanning the portion, a processing unit, connected to the light source and the sensor, for processing the change in light intensity detected by the sensor so as to determine the change from one numerical figure of the decadic wheel to the next numerical figure and to translate the change into at least a pulse signal; and a housing containing the light source. The sensor and processing unit, are suitable for constituting a darkroom and having an opening facing the meter.