A cellular radio communication system has a number of cells covered by base stations communicating with mobile communication devices. Blue light-, green light-, and red light-detection silicon layers are formed, with the blue light detection layer positioned closest to the backside of the sensor and the red light detection layer positioned farthest from the backside of the sensor. The measured actual pressure ratio is compared with a predetermined reference value, and an error is detected as a function of the result of the comparison. During operation, target values may continue to be utilized or an open loop or closed loop control system may be utilized.