the testo 540 is ideal for the measurement of light intensity (lux). The Hold function allows an easy readout of the measurement values. Max. and min. values are displayed at the press of a button. testo 540 is small and easy to operate. Hold function and max./min. values Incl. calibration protocol Protective cap for safe storage Including wrist strap and belt holder Sensor adapted to spectral sensitivity of the eye Display light