showing a circuit of the detector 10 n shown in fig1 a light detector 150 catches incident signals and converts the signals to electrical signals a light detection circuit 372 detects a weak current and an amplification circuit 373 amplifies the current then an output circuit changes the current to a voltage to be assumed as an external voltage the light detection element 150 is supplied a high driving voltage from a step up circuit 371 a coil 360 generates this high voltage at first a dc voltage 340 is applied to an oscillation circuit 370 to generate a pulse voltage this pulse voltage is applied to the primary side 361 of the coil 360 to generate an ac voltage higher than the pulse voltage at the secondary side 362 of the coil 360 this ac voltage is applied to the step up circuit 371 to generate a driving high supply voltage the temperature detection element 350 is connected to the step up circuit 317 and the detected signal is fed back to the oscillation circuit 370 consequently a stable supply voltage is realized fig1 shows a second embodiment of the present invention each of measuring systems 400 and 401 includes plural light sources 38 n and plural detectors 39 n that are disposed at equal intervals in an array pattern each detector 39 n is structured as a module according to the present invention to improve the portability the use of one unit of this measuring system 400 enables measurement of the freshness etc of food since the light irradiated from a light source 380 is reflected.