Abstract: An illumination flicker measuring device having a photodiode detector producing a signal proportional to the illumination being measured. An input amplifier for increasing the level of the signal produced by the photodiode detector. A capacitor is inserted so as remove the average light output component of the signal produced by the photodiode detector and which is then entered into a rectifier and amplifier so as to remove the lower envelope of the signal and amplify the upper envelope of the signal. A low pass filter is then attached to the rectifier and amplifier so as to remove the 120 Hz ripple produced by the 60 Hz system powering the illumination system. The output of the low pass filter is then passed through a capacitor to remove DC components present and then rectified and amplified again to produce a signal which is proportional to the amplitude of the flicker present in the illumination system.